Copyright © 2004, 2005, 2006, 2007, 2008 Steven Knight
version 1.1.0$CPPPATH
Construction VariableSCONSFLAGS
Environment Variablevariable
=value
Build VariablesThank you for taking the time to read about SCons. SCons is a next-generation software construction tool, or make tool--that is, a software utility for building software (or other files) and keeping built software up-to-date whenever the underlying input files change.
The most distinctive thing about SCons is that its configuration files are actually scripts, written in the Python programming language. This is in contrast to most alternative build tools, which typically invent a new language to configure the build. SCons still has a learning curve, of course, because you have to know what functions to call to set up your build properly, but the underlying syntax used should be familiar to anyone who has ever looked at a Python script.
Paradoxically, using Python as the configuration file format makes SCons easier for non-programmers to learn than the cryptic languages of other build tools, which are usually invented by programmers for other programmers. This is in no small part due to the consistency and readability that are built in to Python. It just so happens that making a real, live scripting language the basis for the configuration files makes it a snap for more accomplished programmers to do more complicated things with builds, as necessary.
There are a few overriding principles we try to live up to in designing and implementing SCons:
First and foremost, by default, SCons guarantees a correct build even if it means sacrificing performance a little. We strive to guarantee the build is correct regardless of how the software being built is structured, how it may have been written, or how unusual the tools are that build it.
Given that the build is correct, we try to make SCons build software as quickly as possible. In particular, wherever we may have needed to slow down the default SCons behavior to guarantee a correct build, we also try to make it easy to speed up SCons through optimization options that let you trade off guaranteed correctness in all end cases for a speedier build in the usual cases.
SCons tries to do as much for you out of the box as reasonable, including detecting the right tools on your system and using them correctly to build the software.
In a nutshell, we try hard to make SCons just "do the right thing" and build software correctly, with a minimum of hassles.
One word of warning as you read through this Guide: Like too much Open Source software out there, the SCons documentation isn't always kept up-to-date with the available features. In other words, there's a lot that SCons can do that isn't yet covered in this User's Guide. (Come to think of it, that also describes a lot of proprietary software, doesn't it?)
Although this User's Guide isn't as complete as we'd like it to be, our development process does emphasize making sure that the SCons man page is kept up-to-date with new features. So if you're trying to figure out how to do something that SCons supports but can't find enough (or any) information here, it would be worth your while to look at the man page to see if the information is covered there. And if you do, maybe you'd even consider contributing a section to the User's Guide so the next person looking for that information won't have to go through the same thing...?
SCons would not exist without a lot of help from a lot of people, many of whom may not even be aware that they helped or served as inspiration. So in no particular order, and at the risk of leaving out someone:
First and foremost, SCons owes a tremendous debt to Bob Sidebotham, the original author of the classic Perl-based Cons tool which Bob first released to the world back around 1996. Bob's work on Cons classic provided the underlying architecture and model of specifying a build configuration using a real scripting language. My real-world experience working on Cons informed many of the design decisions in SCons, including the improved parallel build support, making Builder objects easily definable by users, and separating the build engine from the wrapping interface.
Greg Wilson was instrumental in getting SCons started as a real project when he initiated the Software Carpentry design competition in February 2000. Without that nudge, marrying the advantages of the Cons classic architecture with the readability of Python might have just stayed no more than a nice idea.
The entire SCons team have been absolutely wonderful to work with, and SCons would be nowhere near as useful a tool without the energy, enthusiasm and time people have contributed over the past few years. The "core team" of Chad Austin, Anthony Roach, Bill Deegan, Charles Crain, Steve Leblanc, Greg Noel, Gary Oberbrunner, Greg Spencer and Christoph Wiedemann have been great about reviewing my (and other) changes and catching problems before they get in the code base. Of particular technical note: Anthony's outstanding and innovative work on the tasking engine has given SCons a vastly superior parallel build model; Charles has been the master of the crucial Node infrastructure; Christoph's work on the Configure infrastructure has added crucial Autoconf-like functionality; and Greg has provided excellent support for Microsoft Visual Studio.
Special thanks to David Snopek for contributing his underlying "Autoscons" code that formed the basis of Christoph's work with the Configure functionality. David was extremely generous in making this code available to SCons, given that he initially released it under the GPL and SCons is released under a less-restrictive MIT-style license.
Thanks to Peter Miller for his splendid change management system, Aegis, which has provided the SCons project with a robust development methodology from day one, and which showed me how you could integrate incremental regression tests into a practical development cycle (years before eXtreme Programming arrived on the scene).
And last, thanks to Guido van Rossum for his elegant scripting language, which is the basis not only for the SCons implementation, but for the interface itself.
The best way to contact people involved with SCons, including the author, is through the SCons mailing lists.
If you want to ask general questions about how to use SCons send email to users@scons.tigris.org.
If you want to contact the SCons development community directly, send email to dev@scons.tigris.org.
If you want to receive announcements about SCons, join the low-volume announce@scons.tigris.org mailing list.
This chapter will take you through the basic steps of installing SCons on your system, and building SCons if you don't have a pre-built package available (or simply prefer the flexibility of building it yourself). Before that, however, this chapter will also describe the basic steps involved in installing Python on your system, in case that is necessary. Fortunately, both SCons and Python are very easy to install on almost any system, and Python already comes installed on many systems.
Because SCons is written in Python, you must obviously have Python installed on your system to use SCons. Before you try to install Python, you should check to see if Python is already available on your system by typing python -V (capital 'V') or python --version at your system's command-line prompt.
$ python -V Python 2.5.1 |
And on a Windows system with Python installed:
C:\>python -V Python 2.5.1 |
If Python is not installed on your system, you will see an error message stating something like "command not found" (on UNIX or Linux) or "'python' is not recognized as an internal or external command, operable progam or batch file" (on Windows). In that case, you need to install Python before you can install SCons.
(Note that the -V
option
was added to Python version 2.0,
so if your system only has an earlier version available
you may see an
"Unknown option: -V"
error message.)
The standard location for information about downloading and installing Python is http://www.python.org/download/. See that page for information about how to download and install Python on your system.
SCons will work with any version of Python from 1.5.2 or later. If you need to install Python and have a choice, we recommend using the most recent Python 2.5 version available. Python 2.5 has significant improvements the help speed up the performance of SCons'.
SCons comes pre-packaged for installation on a number of systems, including Linux and Windows systems. You do not need to read this entire section, you should only need to read the section appropriate to the type of system you're running on.
SCons comes in RPM (Red Hat Package Manager) format, pre-built and ready to install on Red Hat Linux, Fedora Core, or any other Linux distribution that uses RPM. Your distribution may already have an SCons RPM built specifically for it; many do, including SuSe, Mandrake and Fedora. You can check for the availability of an SCons RPM on your distribution's download servers, or by consulting an RPM search site like http://www.rpmfind.net/ or http://rpm.pbone.net/.
If your Linux distribution does not already have a specific SCons RPM file, you can download and install from the generic RPM provided by the SCons project. This will install the SCons script(s) in /usr/bin, and the SCons library modules in /usr/lib/scons.
To install from the command line, simply download the appropriate .rpm file, and then run:
# rpm -Uvh scons-0.96-1.noarch.rpm |
Or, you can use a graphical RPM package manager like gnorpm. See your package manager application's documention for specific instructions about how to use it to install a downloaded RPM.
Debian Linux systems use a different package management format that also makes it very easy to install SCons.
If your system is connected to the Internet, you can install the latest official Debian package by running:
# apt-get install scons |
SCons provides a Windows installer that makes installation extremely easy. Download the scons-0.95.win32.exe file from the SCons download page at http://www.scons.org/download.html. Then all you need to do is execute the file (usually by clicking on its icon in Windows Explorer). These will take you through a small sequence of windows that will install SCons on your system.
If a pre-built SCons package is not available for your system, then you can still easily build and install SCons using the native Python distutils package.
The first step is to download either the scons-1.1.0.tar.gz or scons-1.1.0.zip, which are available from the SCons download page at http://www.scons.org/download.html.
Unpack the archive you downloaded, using a utility like tar on Linux or UNIX, or WinZip on Windows. This will create a directory called scons-1.1.0, usually in your local directory. Then change your working directory to that directory and install SCons by executing the following commands:
# cd scons-1.1.0 # python setup.py install |
This will build SCons, install the scons script in the default system scripts directory (/usr/local/bin or C:\Python25\Scripts), and will install the SCons build engine in an appropriate stand-alone library directory (/usr/local/lib/scons or C:\Python25\scons). Because these are system directories, you may need root (on Linux or UNIX) or Administrator (on Windows) privileges to install SCons like this.
The SCons setup.py script has some extensions that support easy installation of multiple versions of SCons in side-by-side locations. This makes it easier to download and experiment with different versions of SCons before moving your official build process to a new version, for example.
To install SCons in a version-specific location,
add the --version-lib
option
when you call setup.py:
# python setup.py install --version-lib |
This will install the SCons build engine in the /usr/lib/scons-1.1.0 or C:\Python25\scons-1.1.0 directory, for example.
If you use the --version-lib
option
the first time you install SCons,
you do not need to specify it each time you install
a new version.
The SCons setup.py script
will detect the version-specific directory name(s)
and assume you want to install all versions
in version-specific directories.
You can override that assumption in the future
by explicitly specifying the --standalone-lib
option.
You can install SCons in locations other than
the default by specifying the --prefix=
option:
# python setup.py install --prefix=/opt/scons |
This would install the scons script in /opt/scons/bin and the build engine in /opt/scons/lib/scons,
Note that you can specify both the --prefix=
and the --version-lib
options
at the same type,
in which case setup.py
will install the build engine
in a version-specific directory
relative to the specified prefix.
Adding --version-lib
to the
above example would install the build engine in
/opt/scons/lib/scons-1.1.0.
If you don't have the right privileges to install SCons in a system location, simply use the --prefix= option to install it in a location of your choosing. For example, to install SCons in appropriate locations relative to the user's $HOME directory, the scons script in $HOME/bin and the build engine in $HOME/lib/scons, simply type:
$ python setup.py install --prefix=$HOME |
You may, of course, specify any other location you prefer,
and may use the --version-lib
option
if you would like to install version-specific directories
relative to the specified prefix.
In this chapter, you will see several examples of very simple build configurations using SCons, which will demonstrate how easy it is to use SCons to build programs from several different programming languages on different types of systems.
Here's the famous "Hello, World!" program in C:
int main() { printf("Hello, world!\n"); } |
And here's how to build it using SCons. Enter the following into a file named SConstruct:
Program('hello.c') |
This minimal configuration file gives SCons two pieces of information: what you want to build (an executable program), and the input file from which you want it built (the hello.c file). Program is a builder_method, a Python call that tells SCons that you want to build an executable program.
That's it. Now run the scons command to build the program. On a POSIX-compliant system like Linux or UNIX, you'll see something like:
% scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cc -o hello.o -c hello.c cc -o hello hello.o scons: done building targets. |
On a Windows system with the Microsoft Visual C++ compiler, you'll see something like:
C:\>scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:hello.exe hello.obj scons: done building targets. |
First, notice that you only need to specify the name of the source file, and that SCons correctly deduces the names of the object and executable files to be built from the base of the source file name.
Second, notice that the same input SConstruct file, without any changes, generates the correct output file names on both systems: hello.o and hello on POSIX systems, hello.obj and hello.exe on Windows systems. This is a simple example of how SCons makes it extremely easy to write portable software builds.
(Note that we won't provide duplicate side-by-side POSIX and Windows output for all of the examples in this guide; just keep in mind that, unless otherwise specified, any of the examples should work equally well on both types of systems.)
The Program builder method is only one of many builder methods that SCons provides to build different types of files. Another is the Object builder method, which tells SCons to build an object file from the specified source file:
Object('hello.c') |
Now when you run the scons command to build the program, it will build just the hello.o object file on a POSIX system:
% scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cc -o hello.o -c hello.c scons: done building targets. |
And just the hello.obj object file on a Windows system (with the Microsoft Visual C++ compiler):
C:\>scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cl /Fohello.obj /c hello.c /nologo scons: done building targets. |
SCons also makes building with Java extremely easy. Unlike the Program and Object builder methods, however, the Java builder method requires that you specify the name of a destination directory in which you want the class files placed, followed by the source directory in which the .java files live:
Java('classes', 'src') |
If the src directory contains a single hello.java file, then the output from running the scons command would look something like this (on a POSIX system):
% scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... javac -d classes -sourcepath src src/hello.java scons: done building targets. |
We'll cover Java builds in more detail, including building Java archive (.jar) and other types of file, in the Chapter called Java Builds.
When using SCons, it is unnecessary to add special commands or target names to clean up after a build. Instead, you simply use the -c or --clean option when you invoke SCons, and SCons removes the appropriate built files. So if we build our example above and then invoke scons -c afterwards, the output on POSIX looks like:
% scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cc -o hello.o -c hello.c cc -o hello hello.o scons: done building targets. % scons -c scons: Reading SConscript files ... scons: done reading SConscript files. scons: Cleaning targets ... Removed hello.o Removed hello scons: done cleaning targets. |
And the output on Windows looks like:
C:\>scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:hello.exe hello.obj scons: done building targets. C:\>scons -c scons: Reading SConscript files ... scons: done reading SConscript files. scons: Cleaning targets ... Removed hello.obj Removed hello.exe scons: done cleaning targets. |
Notice that SCons changes its output to tell you that it is Cleaning targets ... and done cleaning targets.
If you're used to build systems like Make you've already figured out that the SConstruct file is the SCons equivalent of a Makefile. That is, the SConstruct file is the input file that SCons reads to control the build.
There is, however, an important difference between an SConstruct file and a Makefile: the SConstruct file is actually a Python script. If you're not already familiar with Python, don't worry. This User's Guide will introduce you step-by-step to the relatively small amount of Python you'll need to know to be able to use SCons effectively. And Python is very easy to learn.
One aspect of using Python as the scripting language is that you can put comments in your SConstruct file using Python's commenting convention; that is, everything between a '#' and the end of the line will be ignored:
# Arrange to build the "hello" program. Program('hello.c') # "hello.c" is the source file. |
You'll see throughout the remainder of this Guide that being able to use the power of a real scripting language can greatly simplify the solutions to complex requirements of real-world builds.
One important way in which the SConstruct file is not exactly like a normal Python script, and is more like a Makefile, is that the order in which the SCons functions are called in the SConstruct file does not affect the order in which SCons actually builds the programs and object files you want it to build.[1] In other words, when you call the Program builder (or any other builder method), you're not telling SCons to build the program at the instant the builder method is called. Instead, you're telling SCons to build the program that you want, for example, a program built from a file named hello.c, and it's up to SCons to build that program (and any other files) whenever it's necessary. (We'll learn more about how SCons decides when building or rebuilding a file is necessary in the Chapter called Dependencies, below.)
SCons reflects this distinction between calling a builder method like Program> and actually building the program by printing the status messages that indicate when it's "just reading" the SConstruct file, and when it's actually building the target files. This is to make it clear when SCons is executing the Python statements that make up the SConstruct file, and when SCons is actually executing the commands or other actions to build the necessary files.
Let's clarify this with an example. Python has a print statement that prints a string of characters to the screen. If we put print statements around our calls to the Program builder method:
print "Calling Program('hello.c')" Program('hello.c') print "Calling Program('goodbye.c')" Program('goodbye.c') print "Finished calling Program()" |
Then when we execute SCons, we see the output from the print statements in between the messages about reading the SConscript files, indicating that that is when the Python statements are being executed:
% scons scons: Reading SConscript files ... Calling Program('hello.c') Calling Program('goodbye.c') Finished calling Program() scons: done reading SConscript files. scons: Building targets ... cc -o goodbye.o -c goodbye.c cc -o goodbye goodbye.o cc -o hello.o -c hello.c cc -o hello hello.o scons: done building targets. |
Notice also that SCons built the goodbye program first, even though the "reading SConscript" output shows that we called Program('hello.c') first in the SConstruct file.
You've already seen how SCons prints some messages about what it's doing, surrounding the actual commands used to build the software:
C:\>scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:hello.exe hello.obj scons: done building targets. |
These messages emphasize the order in which SCons does its work: all of the configuration files (generically referred to as SConscript files) are read and executed first, and only then are the target files built. Among other benefits, these messages help to distinguish between errors that occur while the configuration files are read, and errors that occur while targets are being built.
One drawback, of course, is that these messages clutter the output. Fortunately, they're easily disabled by using the -Q option when invoking SCons:
C:\>scons -Q cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:hello.exe hello.obj |
Because we want this User's Guide to focus on what SCons is actually doing, we're going to use the -Q option to remove these messages from the output of all the remaining examples in this Guide.
In this chapter, you will see several examples of very simple build configurations using SCons, which will demonstrate how easy it is to use SCons to build programs from several different programming languages on different types of systems.
You've seen that when you call the Program builder method, it builds the resulting program with the same base name as the source file. That is, the following call to build an executable program from the hello.c source file will build an executable program named hello on POSIX systems, and an executable program named hello.exe on Windows systems:
Program('hello.c') |
If you want to build a program with a different name than the base of the source file name, you simply put the target file name to the left of the source file name:
Program('new_hello', 'hello.c') |
(SCons requires the target file name first, followed by the source file name, so that the order mimics that of an assignment statement in most programming languages, including Python: "program = source files".)
Now SCons will build an executable program named new_hello when run on a POSIX system:
% scons -Q cc -o hello.o -c hello.c cc -o new_hello hello.o |
And SCons will build an executable program named new_hello.exe when run on a Windows system:
C:\>scons -Q cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:new_hello.exe hello.obj |
You've just seen how to configure SCons to compile a program from a single source file. It's more common, of course, that you'll need to build a program from many input source files, not just one. To do this, you need to put the source files in a Python list (enclosed in square brackets), like so:
Program(['prog.c', 'file1.c', 'file2.c']) |
A build of the above example would look like:
% scons -Q cc -o file1.o -c file1.c cc -o file2.o -c file2.c cc -o prog.o -c prog.c cc -o prog prog.o file1.o file2.o |
Notice that SCons deduces the output program name from the first source file specified in the list--that is, because the first source file was prog.c, SCons will name the resulting program prog (or prog.exe on a Windows system). If you want to specify a different program name, then (as we've seen in the previous section) you slide the list of source files over to the right to make room for the output program file name. (SCons puts the output file name to the left of the source file names so that the order mimics that of an assignment statement: "program = source files".) This makes our example:
Program('program', ['prog.c', 'file1.c', 'file2.c']) |
On Linux, a build of this example would look like:
% scons -Q cc -o file1.o -c file1.c cc -o file2.o -c file2.c cc -o prog.o -c prog.c cc -o program prog.o file1.o file2.o |
Or on Windows:
C:\>scons -Q cl /Fofile1.obj /c file1.c /nologo cl /Fofile2.obj /c file2.c /nologo cl /Foprog.obj /c prog.c /nologo link /nologo /OUT:program.exe prog.obj file1.obj file2.obj |
You can also use the Glob function to find all files matching a certain template, using the standard shell pattern matching characters *, ? and [abc] to match any of a, b or c. [!abc] is also supported, to match any character except a, b or c. This makes many multi-source-file builds quite easy:
Program('program', Glob('*.c')) |
The SCons man page has more details on using Glob with Variant directories and Repositories, and returning strings rather than Nodes.
We've now shown you two ways to specify the source for a program, one with a list of files:
Program('hello', ['file1.c', 'file2.c']) |
And one with a single file:
Program('hello', 'hello.c') |
You could actually put a single file name in a list, too, which you might prefer just for the sake of consistency:
Program('hello', ['hello.c']) |
SCons functions will accept a single file name in either form. In fact, internally, SCons treats all input as lists of files, but allows you to omit the square brackets to cut down a little on the typing when there's only a single file name.
![]() | Although SCons functions are forgiving about whether or not you use a string vs. a list for a single file name, Python itself is more strict about treating lists and strings differently. So where SCons allows either a string or list:
Trying to do "Python things" that mix strings and lists will cause errors or lead to incorrect results:
|
One drawback to the use of a Python list for source files is that each file name must be enclosed in quotes (either single quotes or double quotes). This can get cumbersome and difficult to read when the list of file names is long. Fortunately, SCons and Python provide a number of ways to make sure that the SConstruct file stays easy to read.
To make long lists of file names easier to deal with, SCons provides a Split function that takes a quoted list of file names, with the names separated by spaces or other white-space characters, and turns it into a list of separate file names. Using the Split function turns the previous example into:
Program('program', Split('main.c file1.c file2.c')) |
(If you're already familiar with Python, you'll have realized that this is similar to the split() method in the Python standard string module. Unlike the string.split() method, however, the Split function does not require a string as input and will wrap up a single non-string object in a list, or return its argument untouched if it's already a list. This comes in handy as a way to make sure arbitrary values can be passed to SCons functions without having to check the type of the variable by hand.)
Putting the call to the Split function inside the Program call can also be a little unwieldy. A more readable alternative is to assign the output from the Split call to a variable name, and then use the variable when calling the Program function:
src_files = Split('main.c file1.c file2.c') Program('program', src_files) |
Lastly, the Split function doesn't care how much white space separates the file names in the quoted string. This allows you to create lists of file names that span multiple lines, which often makes for easier editing:
src_files = Split("""main.c file1.c file2.c""") Program('program', src_files) |
(Note in this example that we used the Python "triple-quote" syntax, which allows a string to contain multiple lines. The three quotes can be either single or double quotes.)
SCons also allows you to identify the output file and input source files using Python keyword arguments. The output file is known as the target, and the source file(s) are known (logically enough) as the source. The Python syntax for this is:
src_files = Split('main.c file1.c file2.c') Program(target = 'program', source = src_files) |
Because the keywords explicitly identify what each argument is, you can actually reverse the order if you prefer:
src_files = Split('main.c file1.c file2.c') Program(source = src_files, target = 'program') |
Whether or not you choose to use keyword arguments to identify the target and source files, and the order in which you specify them when using keywords, are purely personal choices; SCons functions the same regardless.
In order to compile multiple programs within the same SConstruct file, simply call the Program method multiple times, once for each program you need to build:
Program('foo.c') Program('bar', ['bar1.c', 'bar2.c']) |
SCons would then build the programs as follows:
% scons -Q cc -o bar1.o -c bar1.c cc -o bar2.o -c bar2.c cc -o bar bar1.o bar2.o cc -o foo.o -c foo.c cc -o foo foo.o |
Notice that SCons does not necessarily build the programs in the same order in which you specify them in the SConstruct file. SCons does, however, recognize that the individual object files must be built before the resulting program can be built. We'll discuss this in greater detail in the "Dependencies" section, below.
It's common to re-use code by sharing source files between multiple programs. One way to do this is to create a library from the common source files, which can then be linked into resulting programs. (Creating libraries is discussed in the Chapter called Building and Linking with Libraries, below.)
A more straightforward, but perhaps less convenient, way to share source files between multiple programs is simply to include the common files in the lists of source files for each program:
Program(Split('foo.c common1.c common2.c')) Program('bar', Split('bar1.c bar2.c common1.c common2.c')) |
SCons recognizes that the object files for the common1.c and common2.c source files each only need to be built once, even though the resulting object files are each linked in to both of the resulting executable programs:
% scons -Q cc -o bar1.o -c bar1.c cc -o bar2.o -c bar2.c cc -o common1.o -c common1.c cc -o common2.o -c common2.c cc -o bar bar1.o bar2.o common1.o common2.o cc -o foo.o -c foo.c cc -o foo foo.o common1.o common2.o |
If two or more programs share a lot of common source files, repeating the common files in the list for each program can be a maintenance problem when you need to change the list of common files. You can simplify this by creating a separate Python list to hold the common file names, and concatenating it with other lists using the Python + operator:
common = ['common1.c', 'common2.c'] foo_files = ['foo.c'] + common bar_files = ['bar1.c', 'bar2.c'] + common Program('foo', foo_files) Program('bar', bar_files) |
This is functionally equivalent to the previous example.
It's often useful to organize large software projects by collecting parts of the software into one or more libraries. SCons makes it easy to create libraries and to use them in the programs.
You build your own libraries by specifying Library instead of Program:
Library('foo', ['f1.c', 'f2.c', 'f3.c']) |
SCons uses the appropriate library prefix and suffix for your system. So on POSIX or Linux systems, the above example would build as follows (although ranlib may not be called on all systems):
% scons -Q cc -o f1.o -c f1.c cc -o f2.o -c f2.c cc -o f3.o -c f3.c ar rc libfoo.a f1.o f2.o f3.o ranlib libfoo.a |
On a Windows system, a build of the above example would look like:
C:\>scons -Q cl /Fof1.obj /c f1.c /nologo cl /Fof2.obj /c f2.c /nologo cl /Fof3.obj /c f3.c /nologo lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj |
The rules for the target name of the library are similar to those for programs: if you don't explicitly specify a target library name, SCons will deduce one from the name of the first source file specified, and SCons will add an appropriate file prefix and suffix if you leave them off.
The previous example shows building a library from a list of source files. You can, however, also give the Library call object files, and it will correctly realize In fact, you can arbitrarily mix source code files and object files in the source list:
Library('foo', ['f1.c', 'f2.o', 'f3.c', 'f4.o']) |
And SCons realizes that only the source code files must be compiled into object files before creating the final library:
% scons -Q cc -o f1.o -c f1.c cc -o f3.o -c f3.c ar rc libfoo.a f1.o f2.o f3.o f4.o ranlib libfoo.a |
Of course, in this example, the object files must already exist for the build to succeed. See the Chapter called Node Objects, below, for information about how you can build object files explicitly and include the built files in a library.
The Library function builds a traditional static library. If you want to be explicit about the type of library being built, you can use the synonym StaticLibrary function instead of Library:
StaticLibrary('foo', ['f1.c', 'f2.c', 'f3.c']) |
There is no functional difference between the StaticLibrary and Library functions.
If you want to build a shared library (on POSIX systems) or a DLL file (on Windows systems), you use the SharedLibrary function:
SharedLibrary('foo', ['f1.c', 'f2.c', 'f3.c']) |
The output on POSIX:
% scons -Q cc -o f1.os -c f1.c cc -o f2.os -c f2.c cc -o f3.os -c f3.c cc -o libfoo.so -shared f1.os f2.os f3.os |
And the output on Windows:
C:\>scons -Q cl /Fof1.obj /c f1.c /nologo cl /Fof2.obj /c f2.c /nologo cl /Fof3.obj /c f3.c /nologo link /nologo /dll /out:foo.dll /implib:foo.lib f1.obj f2.obj f3.obj RegServerFunc(target, source, env) |
Notice again that SCons takes care of building the output file correctly, adding the -shared option for a POSIX compilation, and the /dll option on Windows.
Usually, you build a library
because you want to link it with one or more programs.
You link libraries with a program by specifying
the libraries in the $LIBS
construction variable,
and by specifying the directory in which
the library will be found in the
$LIBPATH
construction variable:
Library('foo', ['f1.c', 'f2.c', 'f3.c']) Program('prog.c', LIBS=['foo', 'bar'], LIBPATH='.') |
Notice, of course, that you don't need to specify a library prefix (like lib) or suffix (like .a or .lib). SCons uses the correct prefix or suffix for the current system.
On a POSIX or Linux system, a build of the above example would look like:
% scons -Q cc -o f1.o -c f1.c cc -o f2.o -c f2.c cc -o f3.o -c f3.c ar rc libfoo.a f1.o f2.o f3.o ranlib libfoo.a cc -o prog.o -c prog.c cc -o prog prog.o -L. -lfoo -lbar |
On a Windows system, a build of the above example would look like:
C:\>scons -Q cl /Fof1.obj /c f1.c /nologo cl /Fof2.obj /c f2.c /nologo cl /Fof3.obj /c f3.c /nologo lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj cl /Foprog.obj /c prog.c /nologo link /nologo /OUT:prog.exe /LIBPATH:. foo.lib bar.lib prog.obj |
As usual, notice that SCons has taken care of constructing the correct command lines to link with the specified library on each system.
Note also that, if you only have a single library to link with, you can specify the library name in single string, instead of a Python list, so that:
Program('prog.c', LIBS='foo', LIBPATH='.') |
is equivalent to:
Program('prog.c', LIBS=['foo'], LIBPATH='.') |
This is similar to the way that SCons handles either a string or a list to specify a single source file.
$LIBPATH
Construction Variable
By default, the linker will only look in
certain system-defined directories for libraries.
SCons knows how to look for libraries
in directories that you specify with the
$LIBPATH
construction variable.
$LIBPATH
consists of a list of
directory names, like so:
Program('prog.c', LIBS = 'm', LIBPATH = ['/usr/lib', '/usr/local/lib']) |
Using a Python list is preferred because it's portable across systems. Alternatively, you could put all of the directory names in a single string, separated by the system-specific path separator character: a colon on POSIX systems:
LIBPATH = '/usr/lib:/usr/local/lib' |
or a semi-colon on Windows systems:
LIBPATH = 'C:\\lib;D:\\lib' |
(Note that Python requires that the backslash separators in a Windows path name be escaped within strings.)
When the linker is executed, SCons will create appropriate flags so that the linker will look for libraries in the same directories as SCons. So on a POSIX or Linux system, a build of the above example would look like:
% scons -Q cc -o prog.o -c prog.c cc -o prog prog.o -L/usr/lib -L/usr/local/lib -lm |
On a Windows system, a build of the above example would look like:
C:\>scons -Q cl /Foprog.obj /c prog.c /nologo link /nologo /OUT:prog.exe /LIBPATH:\usr\lib /LIBPATH:\usr\local\lib m.lib prog.obj |
Note again that SCons has taken care of the system-specific details of creating the right command-line options.
Internally, SCons represents all of the files and directories it knows about as Nodes. These internal objects (not object files) can be used in a variety of ways to make your SConscript files portable and easy to read.
All builder methods return a list of
Node
objects that identify the
target file or files that will be built.
These returned Nodes can be passed
as source files to other builder methods,
For example, suppose that we want to build the two object files that make up a program with different options. This would mean calling the Object builder once for each object file, specifying the desired options:
Object('hello.c', CCFLAGS='-DHELLO') Object('goodbye.c', CCFLAGS='-DGOODBYE') |
One way to combine these object files into the resulting program would be to call the Program builder with the names of the object files listed as sources:
Object('hello.c', CCFLAGS='-DHELLO') Object('goodbye.c', CCFLAGS='-DGOODBYE') Program(['hello.o', 'goodbye.o']) |
The problem with listing the names as strings is that our SConstruct file is no longer portable across operating systems. It won't, for example, work on Windows because the object files there would be named hello.obj and goodbye.obj, not hello.o and goodbye.o.
A better solution is to assign the lists of targets returned by the calls to the Object builder to variables, which we can then concatenate in our call to the Program builder:
hello_list = Object('hello.c', CCFLAGS='-DHELLO') goodbye_list = Object('goodbye.c', CCFLAGS='-DGOODBYE') Program(hello_list + goodbye_list) |
This makes our SConstruct file portable again, the build output on Linux looking like:
% scons -Q cc -o goodbye.o -c -DGOODBYE goodbye.c cc -o hello.o -c -DHELLO hello.c cc -o hello hello.o goodbye.o |
And on Windows:
C:\>scons -Q cl /Fogoodbye.obj /c goodbye.c -DGOODBYE cl /Fohello.obj /c hello.c -DHELLO link /nologo /OUT:hello.exe hello.obj goodbye.obj |
We'll see examples of using the list of nodes returned by builder methods throughout the rest of this guide.
It's worth mentioning here that SCons maintains a clear distinction between Nodes that represent files and Nodes that represent directories. SCons supports File and Dir functions that, repectively, return a file or directory Node:
hello_c = File('hello.c') Program(hello_c) classes = Dir('classes') Java(classes, 'src') |
Normally, you don't need to call File or Dir directly, because calling a builder method automatically treats strings as the names of files or directories, and translates them into the Node objects for you. The File and Dir functions can come in handy in situations where you need to explicitly instruct SCons about the type of Node being passed to a builder or other function, or unambiguously refer to a specific file in a directory tree.
There are also times when you may need to refer to an entry in a file system without knowing in advance whether it's a file or a directory. For those situations, SCons also supports an Entry function, which returns a Node that can represent either a file or a directory.
xyzzy = Entry('xyzzy') |
The returned xyzzy Node will be turned into a file or directory Node the first time it is used by a builder method or other function that requires one vs. the other.
Node
File NamesOne of the most common things you can do with a Node is use it to print the file name that the node represents. For example, the following SConstruct file:
hello_c = File('hello.c') Program(hello_c) classes = Dir('classes') Java(classes, 'src') object_list = Object('hello.c') program_list = Program(object_list) print "The object file is:", object_list[0] print "The program file is:", program_list[0] |
Would print the following file names on a POSIX system:
% scons -Q The object file is: hello.o The program file is: hello cc -o hello.o -c hello.c cc -o hello hello.o |
And the following file names on a Windows system:
C:\>scons -Q The object file is: hello.obj The program file is: hello.exe cl /Fohello.obj /c hello.c /nologo link /nologo /OUT:hello.exe hello.obj |
Node
's File Name as a String
Printing a Node
's name
as described in the previous section
works because the string representation of a Node
is the name of the file.
If you want to do something other than
print the name of the file,
you can fetch it by using the builtin Python
str function.
For example, if you want to use the Python
os.path.exists
to figure out whether a file
exists while the SConstruct file
is being read and executed,
you can fetch the string as follows:
import os.path program_list = Program('hello.c') program_name = str(program_list[0]) if not os.path.exists(program_name): print program_name, "does not exist!" |
Which executes as follows on a POSIX system:
% scons -Q hello does not exist! cc -o hello.o -c hello.c cc -o hello hello.o |
So far we've seen how SCons handles one-time builds. But one of the main functions of a build tool like SCons is to rebuild only the necessary things when source files change--or, put another way, SCons should not waste time rebuilding things that have already been built. You can see this at work simply by re-invoking SCons after building our simple hello example:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q scons: `.' is up to date. |
The second time it is executed, SCons realizes that the hello program is up-to-date with respect to the current hello.c source file, and avoids rebuilding it. You can see this more clearly by naming the hello program explicitly on the command line:
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. |
Note that SCons reports "...is up to date" only for target files named explicitly on the command line, to avoid cluttering the output.
Another aspect of avoiding unnecessary rebuilds is the fundamental build tool behavior of rebuilding things when an input file changes, so that the built software is up to date. By default, SCons keeps track of this through an MD5 signature, or checksum, of the contents of each file, although you can easily configure SCons to use the modification times (or time stamps) instead. You can even specify your own Python function for deciding if an input file has changed.
By default, SCons keeps track of whether a file has changed based on an MD5 checksum of the file's contents, not the file's modification time. This means that you may be surprised by the default SCons behavior if you are used to the Make convention of forcing a rebuild by updating the file's modification time (using the touch command, for example):
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % touch hello.c % scons -Q hello scons: `hello' is up to date. |
Even though the file's modification time has changed, SCons realizes that the contents of the hello.c file have not changed, and therefore that the hello program need not be rebuilt. This avoids unnecessary rebuilds when, for example, someone rewrites the contents of a file without making a change. But if the contents of the file really do change, then SCons detects the change and rebuilds the program as required:
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % edit hello.c [CHANGE THE CONTENTS OF hello.c] % scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o |
Note that you can, if you wish, specify this default behavior (MD5 signatures) explicitly using the Decider function as follows:
Program('hello.c') Decider('MD5') |
You can also use the string 'content' as a synonym for 'MD5' when calling the Decider function.
Using MD5 Signatures to decide if an input file has changed has one surprising benefit: if a source file has been changed in such a way that the contents of the rebuilt target file(s) will be exactly the same as the last time the file was built, then any "downstream" target files that depend on the rebuilt-but-not-changed target file actually need not be rebuilt.
So if, for example, a user were to only change a comment in a hello.c file, then the rebuilt hello.o file would be exactly the same as the one previously built (assuming the compiler doesn't put any build-specific information in the object file). SCons would then realize that it would not need to rebuild the hello program as follows:
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % edit hello.c [CHANGE A COMMENT IN hello.c] % scons -Q hello cc -o hello.o -c hello.c scons: `hello' is up to date. |
In essence, SCons "short-circuits" any dependent builds when it realizes that a target file has been rebuilt to exactly the same file as the last build. This does take some extra processing time to read the contents of the target (hello.o) file, but often saves time when the rebuild that was avoided would have been time-consuming and expensive.
If you prefer, you can configure SCons to use the modification time of a file, not the file contents, when deciding if a target needs to be rebuilt. SCons gives you two ways to use time stamps to decide if an input file has changed since the last time a target has been built.
The most familiar way to use time stamps is the way Make does: that is, have SCons decide and target must be rebuilt if if a source file's modification time is newer than the target file. To do this, call the Decider function as follows:
Program('hello.c') Decider('timestamp-newer') |
This makes SCons act like Make when a file's modification time is updated (using the touch command, for example):
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % touch hello.c % scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o |
And, in fact, because this behavior is the same as the behavior of Make, you can also use the string 'make' as a synonym for 'timestamp-newer' when calling the Decider function:
Program('hello.c') Decider('make') |
One drawback to using times stamps exactly like Make is that if an input file's modification time suddenly becomes older than a target file, the target file will not be rebuilt. This can happen if an old copy of a source file is restored from a backup archive, for example. The contents of the restored file will likely be different than they were the last time a dependent target was built, but the target won't be rebuilt because the modification time of the source file is not newer than the target.
Because SCons actually stores information about the source files' time stamps whenever a target is built, it can handle this situation by checking for an exact match of the source file time stamp, instead of just whether or not the source file is newer than the target file. To do this, specify the argument 'timestamp-match' when calling the Decider function:
Program('hello.c') Decider('timestamp-match') |
When configured this way, SCons will rebuild a target whenever a source file's modification time has changed. So if we use the touch -t option to change the modification time of hello.c to an old date (January 1, 1989), SCons will still rebuild the target file:
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % touch -t 198901010000 hello.c % scons -Q hello cc -o hello.o -c hello.c scons: `hello' is up to date. |
In general, the only reason to prefer timestamp-newer instead of timestamp-match, would be if you have some specific reason to require this Make-like behavior of not rebuilding a target when an otherwise-modified source file is older.
As a performance enhancement, SCons provides a way to use MD5 checksums of file contents but to only read the contents whenever the file's timestamp has changed. To do this, call the Decider function with 'MD5-timestamp' argument as follows:
Program('hello.c') Decider('MD5-timestamp') |
So configured, SCons will still behave like it does when using Decider('MD5'):
% scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % touch hello.c % scons -Q hello scons: `hello' is up to date. % edit hello.c [CHANGE THE CONTENTS OF hello.c] % scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o |
However, the second call to SCons in the above output, when the build is up-to-date, will have been performed by simply looking at the modification time of the hello.c file, not by opening it and performing an MD5 checksum calcuation on its contents. This can significantly speed up many up-to-date builds.
The only drawback to using Decider('MD5-timestamp') is that SCons will not rebuild a target file if a source file was modified within one second of the last time SCons built the file. While most developers are programming, this isn't a problem in practice, since it's unlikely that someone will have built and then thought quickly enought to make a substantive change to a source file within one second. Certain build scripts or continuous integration tools may, however, rely on the ability to applying changes to files automatically and then rebuild as quickly as possible, in which case use of Decider('MD5-timestamp') may not be appropriate.
The different string values that we've passed to the Decider function are essentially used by SCons to pick one of several specific internal functions that implement various ways of deciding if a dependency (usually a source file) has changed since a target file has been built. As it turns out, you can also supply your own function to decide if a dependency has changed.
For example, suppose we have an input file that contains a lot of data, in some specific regular format, that is used to rebuild a lot of different target files, but each target file really only depends on one particular section of the input file. We'd like to have each target file depend on only its section of the input file. However, since the input file may contain a lot of data, we only want to open the input file if its timestamp has changed. This could done with a custom Decider function that might look something like this:
Program('hello.c') def decide_if_changed(dependency, target, prev_ni): if self.get_timestamp() != prev_ni.timestamp: dep = str(dependency) tgt = str(target) if specific_part_of_file_has_changed(dep, tgt): return True return False Decider(decide_if_changed) |
Note that in the function definition,
the dependency
(input file) is the first argument,
and then the target
.
Both of these are passed to the functions as
SCons Node
objects,
which we convert to strings using the Python
str().
The third argument, prev_ni
,
is an object that holds the
signature or timestamp information
that was recorded about the dependency
the last time the target was built.
A prev_ni
object can hold
different information,
depending on the type of thing that the
dependency
argument represents.
For normal files,
the prev_ni
object
has the following attributes:
The content signature,
or MD5 checksum, of the contents of the
dependency
file the list time the target
was built.
The size in bytes of the dependency
file the list time the target was built.
The modification time of the dependency
file the list time the target
was built.
Note that ignoring some of the arguments in your custom Decider function is a perfectly normal thing to do, if they don't impact the way you want to decide if the dependency file has changed.
The previous examples have all demonstrated calling the global Decider function to configure all dependency decisions that SCons makes. Sometimes, however, you want to be able to configure different decision-making for different targets. When that's necessary, you can use the env.Decider method to affect only the configuration decisions for targets built with a specific construction environment.
For example, if we arbitrarily want to build one program using MD5 checkums and another use file modification times from the same source we might configure it this way:
env1 = Environment(CPPPATH = ['.']) env2 = env1.Clone() env2.Decider('timestamp-match') env1.Program('prog-MD5', 'program1.c') env2.Program('prog-timestamp', 'program2.c') |
If both of the programs include the same inc.h file, then updating the modification time of inc.h (using the touch command) will cause only prog-timestamp to be rebuilt:
% scons -Q cc -o program1.o -c -I. program1.c cc -o prog-MD5 program1.o cc -o program2.o -c -I. program2.c cc -o prog-timestamp program2.o % touch inc.h % scons -Q cc -o program2.o -c -I. program2.c cc -o prog-timestamp program2.o |
SCons still supports two functions that used to be the primary methods for configuring the decision about whether or not an input file has changed. Although they're not officially deprecated yet, their use is discouraged, mainly because they rely on a somewhat confusing distinction between how source files and target files are handled. These functions are documented here mainly in case you encounter them in existing SConscript files.
The SourceSignatures function is fairly straightforward, and supports two different argument values to configure whether source file changes should be decided using MD5 signatures:
Program('hello.c') SourceSignatures('MD5') |
Or using time stamps:
Program('hello.c') SourceSignatures('timestamp') |
These are roughly equivalent to specifying Decider('MD5') or Decider('timestamp-match'), respectively, although it only affects how SCons makes decisions about dependencies on source files--that is, files that are not built from any other files.
The TargetSignatures function specifies how SCons decides when a target file has changed when it is used as a dependency of (input to) another target--that is, the TargetSignatures function configures how the signatures of "intermediate" target files are used when deciding if a "downstream" target file must be rebuilt. [2]
The TargetSignatures function supports the same 'MD5' and 'timestamp' argument values that are supported by the SourceSignatures, with the same meanings, but applied to target files. That is, in the example:
Program('hello.c') TargetSignatures('MD5') |
The MD5 checksum of the hello.o target file will be used to decide if it has changed since the last time the "downstream" hello target file was built. And in the example:
Program('hello.c') TargetSignatures('timestamp') |
The modification time of the hello.o target file will be used to decide if it has changed since the last time the "downstream" hello target file was built.
The TargetSignatures function supports two additional argument values: 'source' and 'build'. The 'source' argument specifies that decisions involving whether target files have changed since a previous build should use the same behavior for the decisions configured for source files (using the SourceSignatures function). So in the example:
Program('hello.c') TargetSignatures('source') SourceSignatures('timestamp') |
All files, both targets and sources, will use modification times when deciding if an input file has changed since the last time a target was built.
Lastly, the 'build' argument specifies that SCons should examine the build status of a target file and always rebuild a "downstream" target if the target file was itself rebuilt, without re-examining the contents or timestamp of the newly-built target file. If the target file was not rebuilt during this scons invocation, then the target file will be examined the same way as configured by the SourceSignature call to decide if it has changed.
This mimics the behavior of build signatures in earlier versions of SCons. A build signature re-combined signatures of all the input files that went into making the target file, so that the target file itself did not need to have its contents read to compute an MD5 signature. This can improve performance for some configurations, but is generally not as effective as using Decider('MD5-timestamp').
$CPPPATH
Construction VariableNow suppose that our "Hello, World!" program actually has an #include line to include the hello.h file in the compilation:
#include <hello.h> int main() { printf("Hello, %s!\n", string); } |
And, for completeness, the hello.h file looks like this:
#define string "world" |
In this case, we want SCons to recognize that, if the contents of the hello.h file change, the hello program must be recompiled. To do this, we need to modify the SConstruct file like so:
Program('hello.c', CPPPATH = '.') |
The $CPPPATH
value
tells SCons to look in the current directory
('.')
for any files included by C source files
(.c or .h files).
With this assignment in the SConstruct file:
% scons -Q hello cc -o hello.o -c -I. hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. % edit hello.h [CHANGE THE CONTENTS OF hello.h] % scons -Q hello cc -o hello.o -c -I. hello.c cc -o hello hello.o |
First, notice that SCons
added the -I. argument
from the $CPPPATH
variable
so that the compilation would find the
hello.h file in the local directory.
Second, realize that SCons knows that the hello program must be rebuilt because it scans the contents of the hello.c file for the #include lines that indicate another file is being included in the compilation. SCons records these as implicit dependencies of the target file, Consequently, when the hello.h file changes, SCons realizes that the hello.c file includes it, and rebuilds the resulting hello program that depends on both the hello.c and hello.h files.
Like the $LIBPATH
variable,
the $CPPPATH
variable
may be a list of directories,
or a string separated by
the system-specific path separation character
(':' on POSIX/Linux, ';' on Windows).
Either way, SCons creates the
right command-line options
so that the following example:
Program('hello.c', CPPPATH = ['include', '/home/project/inc']) |
Will look like this on POSIX or Linux:
% scons -Q hello cc -o hello.o -c -Iinclude -I/home/project/inc hello.c cc -o hello hello.o |
And like this on Windows:
C:\>scons -Q hello.exe cl /Fohello.obj /c hello.c /nologo /Iinclude /I\home\project\inc link /nologo /OUT:hello.exe hello.obj |
Scanning each file for #include lines does take some extra processing time. When you're doing a full build of a large system, the scanning time is usually a very small percentage of the overall time spent on the build. You're most likely to notice the scanning time, however, when you rebuild all or part of a large system: SCons will likely take some extra time to "think about" what must be built before it issues the first build command (or decides that everything is up to date and nothing must be rebuilt).
In practice, having SCons scan files saves time relative to the amount of potential time lost to tracking down subtle problems introduced by incorrect dependencies. Nevertheless, the "waiting time" while SCons scans files can annoy individual developers waiting for their builds to finish. Consequently, SCons lets you cache the implicit dependencies that its scanners find, for use by later builds. You can do this by specifying the --implicit-cache option on the command line:
% scons -Q --implicit-cache hello cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. |
If you don't want to specify --implicit-cache on the command line each time, you can make it the default behavior for your build by setting the implicit_cache option in an SConscript file:
SetOption('implicit_cache', 1) |
SCons does not cache implicit dependencies like this by default because the --implicit-cache causes SCons to simply use the implicit dependencies stored during the last run, without any checking for whether or not those dependencies are still correct. Specifically, this means --implicit-cache instructs SCons to not rebuild "correctly" in the following cases:
When --implicit-cache is used, SCons will ignore any changes that
may have been made to search paths
(like $CPPPATH
or $LIBPATH
,).
This can lead to SCons not rebuilding a file if a change to
$CPPPATH
would normally cause a different, same-named file from
a different directory to be used.
When --implicit-cache is used, SCons will not detect if a same-named file has been added to a directory that is earlier in the search path than the directory in which the file was found last time.
When using cached implicit dependencies, sometimes you want to "start fresh" and have SCons re-scan the files for which it previously cached the dependencies. For example, if you have recently installed a new version of external code that you use for compilation, the external header files will have changed and the previously-cached implicit dependencies will be out of date. You can update them by running SCons with the --implicit-deps-changed option:
% scons -Q --implicit-deps-changed hello cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. |
In this case, SCons will re-scan all of the implicit dependencies and cache updated copies of the information.
By default when caching dependencies, SCons notices when a file has been modified and re-scans the file for any updated implicit dependency information. Sometimes, however, you may want to force SCons to use the cached implicit dependencies, even if the source files changed. This can speed up a build for example, when you have changed your source files but know that you haven't changed any #include lines. In this case, you can use the --implicit-deps-unchanged option:
% scons -Q --implicit-deps-unchanged hello cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. |
In this case, SCons will assume that the cached implicit dependencies are correct and will not bother to re-scan changed files. For typical builds after small, incremental changes to source files, the savings may not be very big, but sometimes every bit of improved performance counts.
Sometimes a file depends on another file that is not detected by an SCons scanner. For this situation, SCons allows you to specific explicitly that one file depends on another file, and must be rebuilt whenever that file changes. This is specified using the Depends method:
hello = Program('hello.c') Depends(hello, 'other_file') |
% scons -Q hello cc -c hello.c -o hello.o cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. % edit other_file [CHANGE THE CONTENTS OF other_file] % scons -Q hello cc -c hello.c -o hello.o cc -o hello hello.o |
Note that the dependency (the second argument to Depends) may also be a list of Node objects (for example, as returned by a call to a Builder):
hello = Program('hello.c') goodbye = Program('goodbye.c') Depends(hello, goodbye) |
in which case the dependency or dependencies will be built before the target(s):
% scons -Q hello cc -c goodbye.c -o goodbye.o cc -o goodbye goodbye.o cc -c hello.c -o hello.o cc -o hello hello.o |
SCons has built-in scanners for a number of languages. Sometimes these scanners fail to extract certain implicit dependencies due to limitations of the scanner implementation.
The following example illustrates a case where the built-in C scanner is unable to extract the implicit dependency on a header file.
#define FOO_HEADER <foo.h> #include FOO_HEADER int main() { return FOO; } |
% scons -Q cc -o hello.o -c -I. hello.c cc -o hello hello.o % edit foo.h [CHANGE CONTENTS OF foo.h] % scons -Q scons: `.' is up to date. |
Apparently, the scanner does not know about the header dependency. Being not a full-fledged C preprocessor, the scanner does not expand the macro.
In these cases, you may also use the compiler to extract the implicit dependencies. ParseDepends can parse the contents of the compiler output in the style of Make, and explicitly establish all of the listed dependencies.
The following example uses ParseDepends to process a compiler generated dependency file which is generated as a side effect during compilation of the object file:
obj = Object('hello.c', CCFLAGS='-MD -MF hello.d', CPPPATH='.') SideEffect('hello.d', obj) ParseDepends('hello.d') Program('hello', obj) |
% scons -Q cc -o hello.o -c -MD -MF hello.d -I. hello.c cc -o hello hello.o % edit foo.h [CHANGE CONTENTS OF foo.h] % scons -Q cc -o hello.o -c -MD -MF hello.d -I. hello.c |
Parsing dependencies from a compiler-generated .d file has a chicken-and-egg problem, that causes unnecessary rebuilds:
% scons -Q cc -o hello.o -c -MD -MF hello.d -I. hello.c cc -o hello hello.o % scons -Q --debug=explain scons: rebuilding `hello.o' because `foo.h' is a new dependency cc -o hello.o -c -MD -MF hello.d -I. hello.c % scons -Q scons: `.' is up to date. |
In the first pass, the dependency file is generated while the object file is compiled. At that time, SCons does not know about the dependency on foo.h. In the second pass, the object file is regenerated because foo.h is detected as a new dependency.
ParseDepends immediately reads the specified file at invocation time and just returns if the file does not exist. A dependency file generated during the build process is not automatically parsed again. Hence, the compiler-extracted dependencies are not stored in the signature database during the same build pass. This limitation of ParseDepends leads to unnecessary recompilations. Therefore, ParseDepends should only be used if scanners are not available for the employed language or not powerful enough for the specific task.
Sometimes it makes sense to not rebuild a program, even if a dependency file changes. In this case, you would tell SCons specifically to ignore a dependency as follows:
hello = Program('hello.c') Ignore(hello, 'hello.h') |
% scons -Q hello cc -c -o hello.o hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. % edit hello.h [CHANGE THE CONTENTS OF hello.h] % scons -Q hello scons: `hello' is up to date. |
Now, the above example is a little contrived, because it's hard to imagine a real-world situation where you wouldn't want to rebuild hello if the hello.h file changed. A more realistic example might be if the hello program is being built in a directory that is shared between multiple systems that have different copies of the stdio.h include file. In that case, SCons would notice the differences between the different systems' copies of stdio.h and would rebuild hello each time you change systems. You could avoid these rebuilds as follows:
hello = Program('hello.c', CPPPATH=['/usr/include']) Ignore(hello, '/usr/include/stdio.h') |
Ignore can also be used to prevent a generated file from being built by default. This is due to the fact that directories depend on their contents. So to ignore a generated file from the default build, you specify that the directory should ignore the generated file. Note that the file will still be built if the user specifically requests the target on scons command line, or if the file is a dependency of another file which is requested and/or is built by default.
hello_obj=Object('hello.c') hello = Program(hello_obj) Ignore('.',[hello,hello_obj]) |
% scons -Q scons: `.' is up to date. % scons -Q hello cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello scons: `hello' is up to date. |
Occasionally, it may be useful to specify that a certain file or directory must, if necessary, be built or created before some other target is built, but that changes to that file or directory do not require that the target itself be rebuilt. Such a relationship is called an order-only dependency because it only affects the order in which things must be built--the dependency before the target--but it is not a strict dependency relationship because the target should not change in response to changes in the dependent file.
For example, suppose that you want to create a file every time you run a build that identifies the time the build was performed, the version number, etc., and which is included in every program that you build. The version file's contents will change every build. If you specify a normal dependency relationship, then every program that depends on that file would be rebuilt every time you ran SCons. For example, we could use some Python code in a SConstruct file to create a new version.c file with a string containing the current date every time we run SCons, and then link a program with the resulting object file by listing version.c in the sources:
import time version_c_text = """ char *date = "%s"; """ % time.ctime(time.time()) open('version.c', 'w').write(version_c_text) hello = Program(['hello.c', 'version.c']) |
If we list version.c as an actual source file, though, then version.o will get rebuilt every time we run SCons (because the SConstruct file itself changes the contents of version.c) and the hello executable will get re-linked every time (because the version.o file changes):
% scons -Q gcc -o hello.o -c hello.c gcc -o version.o -c version.c gcc -o hello hello.o version.o % scons -Q gcc -o version.o -c version.c gcc -o hello hello.o version.o % scons -Q gcc -o version.o -c version.c gcc -o hello hello.o version.o |
One solution is to use the Requires function to specify that the version.o must be rebuilt before it is used by the link step, but that changes to version.o should not actually cause the hello executable to be re-linked:
import time version_c_text = """ char *date = "%s"; """ % time.ctime(time.time()) open('version.c', 'w').write(version_c_text) version_obj = Object('version.c') hello = Program('hello.c', LINKFLAGS = str(version_obj[0])) Requires(hello, version_obj) |
Notice that because we can no longer list version.c
as one of the sources for the hello program,
we have to find some other way to get it into the link command line.
For this example, we're cheating a bit and stuffing the
object file name (extracted from version_obj
list returned by the Object call)
into the $LINKFLAGS
variable,
because $LINKFLAGS
is already included
in the $LINKCOM
command line.
With these changes, we get the desired behavior of re-building the version.o file, and therefore re-linking the hello executable, only when the hello.c has changed:
% scons -Q cc -o hello.o -c hello.c cc -o version.o -c version.c cc -o hello version.o hello.o % scons -Q scons: `.' is up to date. % edit hello.c [CHANGE THE CONTENTS OF hello.c] % scons -Q cc -o hello.o -c hello.c cc -o hello version.o hello.o % scons -Q scons: `.' is up to date. |
How SCons handles dependencies can also be affected by the AlwaysBuild method. When a file is passed to the AlwaysBuild method, like so:
hello = Program('hello.c') AlwaysBuild(hello) |
Then the specified target file (hello in our example) will always be considered out-of-date and rebuilt whenever that target file is evaluated while walking the dependency graph:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q cc -o hello hello.o |
The AlwaysBuild function has a somewhat misleading name, because it does not actually mean the target file will be rebuilt every single time SCons is invoked. Instead, it means that the target will, in fact, be rebuilt whenever the target file is encountered while evaluating the targets specified on the command line (and their dependencies). So specifying some other target on the command line, a target that does not itself depend on the AlwaysBuild target, will still be rebuilt only if it's out-of-date with respect to its dependencies:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q hello.o scons: `hello.o' is up to date. |
An environment is a collection of values that can affect how a program executes. SCons distinguishes between three different types of environments that can affect the behavior of SCons itself (subject to the configuration in the SConscript files), as well as the compilers and other tools it executes:
The external environment is the set of variables in the user's environment at the time the user runs SCons. These variables are available within the SConscript files through the Python os.environ dictionary. See the Section called Using Values From the External Environment, below.
A construction environment is a distinct object creating within a SConscript file and and which contains values that affect how SCons decides what action to use to build a target, and even to define which targets should be built from which sources. One of the most powerful features of SCons is the ability to create multiple construction environments, including the ability to clone a new, customized construction environment from an existing construction environment. See the Section called Construction Environments, below.
An execution environment is the values that SCons sets when executing an external command (such as a compiler or linker) to build one or more targets. Note that this is not the same as the external environment (see above). See the Section called Controlling the Execution Environment for Issued Commands, below.
Unlike Make, SCons does not automatically copy or import values between different environments (with the exception of explicit clones of construction environments, which inherit values from their parent). This is a deliberate design choice to make sure that builds are, by default, repeatable regardless of the values in the user's external environment. This avoids a whole class of problems with builds where a developer's local build works because a custom variable setting causes a different comiler or build option to be used, but the checked-in change breaks the official build because it uses different environment variable settings.
Note that the SConscript writer can easily arrange for variables to be copied or imported between environments, and this is often very useful (or even downright necessary) to make it easy for developers to customize the build in appropriate ways. The point is not that copying variables between different environments is evil and must always be avoided. Instead, it should be up to the implementer of the build system to make conscious choices about how and when to import a variable from one environment to another, making informed decisions about striking the right balance between making the build repeatable on the one hand and convenient to use on the other.
The external environment
variable settings that
the user has in force
when executing SCons
are available through the normal Python
os.environ
dictionary.
This means that you must add an
import os statuement
to any SConscript file
in which you want to use
values from the user's external environment.
import os |
More usefully, you can use the
os.environ
dictionary in your SConscript
files to initialize construction environments
with values from the user's external environment.
See the next section,
the Section called Construction Environments,
for information on how to do this.
It is rare that all of the software in a large,
complicated system needs to be built the same way.
For example, different source files may need different options
enabled on the command line,
or different executable programs need to be linked
with different libraries.
SCons accommodates these different build
requirements by allowing you to create and
configure multiple construction environments
that control how the software is built.
A construction environment is an object
that has a number of associated
construction variables, each with a name and a value.
(A construction environment also has an attached
set of Builder
methods,
about which we'll learn more later.)
A construction environment is created by the Environment method:
env = Environment() |
By default, SCons initializes every new construction environment with a set of construction variables based on the tools that it finds on your system, plus the default set of builder methods necessary for using those tools. The construction variables are initialized with values describing the C compiler, the Fortran compiler, the linker, etc., as well as the command lines to invoke them.
When you initialize a construction environment you can set the values of the environment's construction variables to control how a program is built. For example:
import os env = Environment(CC = 'gcc', CCFLAGS = '-O2') env.Program('foo.c') |
The construction environment in this example
is still initialized with the same default
construction variable values,
except that the user has explicitly specified use of the
GNU C compiler gcc,
and further specifies that the -O2
(optimization level two)
flag should be used when compiling the object file.
In other words, the explicit initializations of
$CC
and $CCFLAGS
override the default values in the newly-created
construction environment.
So a run from this example would look like:
% scons -Q gcc -o foo.o -c -O2 foo.c gcc -o foo foo.o |
You can fetch individual construction variables using the normal syntax for accessing individual named items in a Python dictionary:
env = Environment() print "CC is:", env['CC'] |
This example SConstruct file doesn't build anything,
but because it's actually a Python script,
it will print the value of $CC
for us:
% scons -Q CC is: cc scons: `.' is up to date. |
A construction environment, however, is actually an object with associated methods, etc. If you want to have direct access to only the dictionary of construction variables, you can fetch this using the Dictionary method:
env = Environment(FOO = 'foo', BAR = 'bar') dict = env.Dictionary() for key in ['OBJSUFFIX', 'LIBSUFFIX', 'PROGSUFFIX']: print "key = %s, value = %s" % (key, dict[key]) |
This SConstruct file will print the specified dictionary items for us on POSIX systems as follows:
% scons -Q key = OBJSUFFIX, value = .o key = LIBSUFFIX, value = .a key = PROGSUFFIX, value = scons: `.' is up to date. |
And on Windows:
C:\>scons -Q key = OBJSUFFIX, value = .obj key = LIBSUFFIX, value = .lib key = PROGSUFFIX, value = .exe scons: `.' is up to date. |
If you want to loop and print the values of all of the construction variables in a construction environment, the Python code to do that in sorted order might look something like:
env = Environment() dict = env.Dictionary() keys = dict.keys() keys.sort() for key in keys: print "construction variable = '%s', value = '%s'" % (key, dict[key]) |
Another way to get information from
a construction environment.
is to use the subst method
on a string containing $ expansions
of construction variable names.
As a simple example,
the example from the previous
section that used
env['CC']
to fetch the value of $CC
could also be written as:
env = Environment() print "CC is:", env.subst('$CC') |
One advantage of using
subst to expand strings is
that construction variables
in the result get re-expanded until
there are no expansions left in the string.
So a simple fetch of a value like
$CCCOM
:
env = Environment(CCFLAGS = '-DFOO') print "CCCOM is:", env['CCCOM'] |
Will print the unexpanded value of $CCCOM
,
showing us the construction
variables that still need to be expanded:
% scons -Q CCCOM is: $CC $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES scons: `.' is up to date. |
Calling the subst method on $CCOM
,
however:
env = Environment(CCFLAGS = '-DFOO') print "CCCOM is:", env.subst('$CCCOM') |
Will recursively expand all of the construction variables prefixed with $ (dollar signs), showing us the final output:
% scons -Q CCCOM is: gcc -DFOO -c -o scons: `.' is up to date. |
Note that because we're not expanding this
in the context of building something
there are no target or source files
for $TARGET
and $SOURCES
to expand.
All of the Builder
functions that we've introduced so far,
like Program and Library,
actually use a default construction environment
that contains settings
for the various compilers
and other tools that
SCons configures by default,
or otherwise knows about
and has discovered on your system.
The goal of the default construction environment
is to make many configurations to "just work"
to build software using
readily available tools
with a minimum of configuration changes.
You can, however, control the settings in the default contstruction environment by using the DefaultEnvironment function to initialize various settings:
DefaultEnvironment(CC = '/usr/local/bin/gcc') |
When configured as above, all calls to the Program or Object Builder will build object files with the /usr/local/bin/gcc compiler.
Note that the DefaultEnvironment function
returns the initialized
default construction environment object,
which can then be manipulated like any
other construction environment.
So the following
would be equivalent to the
previous example,
setting the $CC
variable to /usr/local/bin/gcc
but as a separate step after
the default construction environment has been initialized:
env = DefaultEnvironment() env['CC'] = '/usr/local/bin/gcc' |
One very common use of the DefaultEnvironment function is to speed up SCons initialization. As part of trying to make most default configurations "just work," SCons will actually search the local system for installed compilers and other utilities. This search can take time, especially on systems with slow or networked file systems. If you know which compiler(s) and/or other utilities you want to configure, you can control the search that SCons performs by specifying some specific tool modules with which to initialize the default construction environment:
env = DefaultEnvironment(tools = ['gcc', 'gnulink'], CC = '/usr/local/bin/gcc') |
So the above example would tell SCons to explicitly configure the default environment to use its normal GNU Compiler and GNU Linker settings (without having to search for them, or any other utilities for that matter), and specifically to use the compiler found at /usr/local/bin/gcc.
The real advantage of construction environments is that you can create as many different construction environments as you need, each tailored to a different way to build some piece of software or other file. If, for example, we need to build one program with the -O2 flag and another with the -g (debug) flag, we would do this like so:
opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') opt.Program('foo', 'foo.c') dbg.Program('bar', 'bar.c') |
% scons -Q cc -o bar.o -c -g bar.c cc -o bar bar.o cc -o foo.o -c -O2 foo.c cc -o foo foo.o |
We can even use multiple construction environments to build multiple versions of a single program. If you do this by simply trying to use the Program builder with both environments, though, like this:
opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') opt.Program('foo', 'foo.c') dbg.Program('foo', 'foo.c') |
Then SCons generates the following error:
% scons -Q scons: *** Two environments with different actions were specified for the same target: foo.o File "/home/my/project/SConstruct", line 6, in <module> |
This is because the two Program calls have
each implicitly told SCons to generate an object file named
foo.o,
one with a $CCFLAGS
value of
-O2
and one with a $CCFLAGS
value of
-g.
SCons can't just decide that one of them
should take precedence over the other,
so it generates the error.
To avoid this problem,
we must explicitly specify
that each environment compile
foo.c
to a separately-named object file
using the Object builder, like so:
opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') o = opt.Object('foo-opt', 'foo.c') opt.Program(o) d = dbg.Object('foo-dbg', 'foo.c') dbg.Program(d) |
Notice that each call to the Object builder returns a value, an internal SCons object that represents the object file that will be built. We then use that object as input to the Program builder. This avoids having to specify explicitly the object file name in multiple places, and makes for a compact, readable SConstruct file. Our SCons output then looks like:
% scons -Q cc -o foo-dbg.o -c -g foo.c cc -o foo-dbg foo-dbg.o cc -o foo-opt.o -c -O2 foo.c cc -o foo-opt foo-opt.o |
Sometimes you want more than one construction environment to share the same values for one or more variables. Rather than always having to repeat all of the common variables when you create each construction environment, you can use the Clone method to create a copy of a construction environment.
Like the Environment call that creates a construction environment,
the Clone method takes construction variable assignments,
which will override the values in the copied construction environment.
For example, suppose we want to use gcc
to create three versions of a program,
one optimized, one debug, and one with neither.
We could do this by creating a "base" construction environment
that sets $CC
to gcc,
and then creating two copies,
one which sets $CCFLAGS
for optimization
and the other which sets $CCFLAGS
for debugging:
env = Environment(CC = 'gcc') opt = env.Clone(CCFLAGS = '-O2') dbg = env.Clone(CCFLAGS = '-g') env.Program('foo', 'foo.c') o = opt.Object('foo-opt', 'foo.c') opt.Program(o) d = dbg.Object('foo-dbg', 'foo.c') dbg.Program(d) |
Then our output would look like:
% scons -Q gcc -o foo.o -c foo.c gcc -o foo foo.o gcc -o foo-dbg.o -c -g foo.c gcc -o foo-dbg foo-dbg.o gcc -o foo-opt.o -c -O2 foo.c gcc -o foo-opt foo-opt.o |
You can replace existing construction variable values using the Replace method:
env = Environment(CCFLAGS = '-DDEFINE1') env.Replace(CCFLAGS = '-DDEFINE2') env.Program('foo.c') |
The replacing value (-DDEFINE2 in the above example) completely replaces the value in the construction environment:
% scons -Q cc -o foo.o -c -DDEFINE2 foo.c cc -o foo foo.o |
You can safely call Replace for construction variables that don't exist in the construction environment:
env = Environment() env.Replace(NEW_VARIABLE = 'xyzzy') print "NEW_VARIABLE =", env['NEW_VARIABLE'] |
In this case, the construction variable simply gets added to the construction environment:
% scons -Q NEW_VARIABLE = xyzzy scons: `.' is up to date. |
Because the variables aren't expanded until the construction environment is actually used to build the targets, and because SCons function and method calls are order-independent, the last replacement "wins" and is used to build all targets, regardless of the order in which the calls to Replace() are interspersed with calls to builder methods:
env = Environment(CCFLAGS = '-DDEFINE1') print "CCFLAGS =", env['CCFLAGS'] env.Program('foo.c') env.Replace(CCFLAGS = '-DDEFINE2') print "CCFLAGS =", env['CCFLAGS'] env.Program('bar.c') |
The timing of when the replacement actually occurs relative to when the targets get built becomes apparent if we run scons without the -Q option:
% scons scons: Reading SConscript files ... CCFLAGS = -DDEFINE1 CCFLAGS = -DDEFINE2 scons: done reading SConscript files. scons: Building targets ... cc -o bar.o -c -DDEFINE2 bar.c cc -o bar bar.o cc -o foo.o -c -DDEFINE2 foo.c cc -o foo foo.o scons: done building targets. |
Because the replacement occurs while
the SConscript files are being read,
the $CCFLAGS
variable has already been set to
-DDEFINE2
by the time the foo.o target is built,
even though the call to the Replace
method does not occur until later in
the SConscript file.
Sometimes it's useful to be able to specify that a construction variable should be set to a value only if the construction environment does not already have that variable defined You can do this with the SetDefault method, which behaves similarly to the set_default method of Python dictionary objects:
env.SetDefault(SPECIAL_FLAG = '-extra-option') |
This is especially useful when writing your own Tool modules to apply variables to construction environments.
You can append a value to an existing construction variable using the Append method:
env = Environment(CCFLAGS = ['-DMY_VALUE']) env.Append(CCFLAGS = ['-DLAST']) env.Program('foo.c') |
SCons then supplies both the -DMY_VALUE and -DLAST flags when compiling the object file:
% scons -Q cc -o foo.o -c -DMY_VALUE -DLAST foo.c cc -o foo foo.o |
If the construction variable doesn't already exist, the Append method will create it:
env = Environment() env.Append(NEW_VARIABLE = 'added') print "NEW_VARIABLE =", env['NEW_VARIABLE'] |
Which yields:
% scons -Q NEW_VARIABLE = added scons: `.' is up to date. |
Note that the Append function tries to be "smart" about how the new value is appended to the old value. If both are strings, the previous and new strings are simply concatenated. Similarly, if both are lists, the lists are concatenated. If, however, one is a string and the other is a list, the string is added as a new element to the list.
Some times it's useful to add a new value only if the existing construction variable doesn't already contain the value. This can be done using the AppendUnique method:
env.AppendUnique(CCFLAGS=['-g']) |
In the above example,
the -g would be added
only if the $CCFLAGS
variable
does not already contain a -g value.
You can append a value to the beginning of an existing construction variable using the Prepend method:
env = Environment(CCFLAGS = ['-DMY_VALUE']) env.Prepend(CCFLAGS = ['-DFIRST']) env.Program('foo.c') |
SCons then supplies both the -DFIRST and -DMY_VALUE flags when compiling the object file:
% scons -Q cc -o foo.o -c -DFIRST -DMY_VALUE foo.c cc -o foo foo.o |
If the construction variable doesn't already exist, the Prepend method will create it:
env = Environment() env.Prepend(NEW_VARIABLE = 'added') print "NEW_VARIABLE =", env['NEW_VARIABLE'] |
Which yields:
% scons -Q NEW_VARIABLE = added scons: `.' is up to date. |
Like the Append function, the Prepend function tries to be "smart" about how the new value is appended to the old value. If both are strings, the previous and new strings are simply concatenated. Similarly, if both are lists, the lists are concatenated. If, however, one is a string and the other is a list, the string is added as a new element to the list.
Some times it's useful to add a new value to the beginning of a construction variable only if the existing value doesn't already contain the to-be-added value. This can be done using the PrependUnique method:
env.PrependUnique(CCFLAGS=['-g']) |
In the above example,
the -g would be added
only if the $CCFLAGS
variable
does not already contain a -g value.
When SCons builds a target file,
it does not execute the commands with
the same external environment
that you used to execute SCons.
Instead, it uses the dictionary
stored in the $ENV
construction variable
as the external environment
for executing commands.
The most important ramification of this behavior
is that the PATH
environment variable,
which controls where the operating system
will look for commands and utilities,
is not the same as in the external environment
from which you called SCons.
This means that SCons will not, by default,
necessarily find all of the tools
that you can execute from the command line.
The default value of the PATH
environment variable
on a POSIX system
is /usr/local/bin:/bin:/usr/bin.
The default value of the PATH
environment variable
on a Windows system comes from the Windows registry
value for the command interpreter.
If you want to execute any commands--compilers, linkers, etc.--that
are not in these default locations,
you need to set the PATH
value
in the $ENV
dictionary
in your construction environment.
The simplest way to do this is to initialize explicitly the value when you create the construction environment; this is one way to do that:
path = ['/usr/local/bin', '/bin', '/usr/bin'] env = Environment(ENV = {'PATH' : path}) |
Assign a dictionary to the $ENV
construction variable in this way
completely resets the external environment
so that the only variable that will be
set when external commands are executed
will be the PATH
value.
If you want to use the rest of
the values in $ENV
and only
set the value of PATH
,
the most straightforward way is probably:
env['ENV']['PATH'] = ['/usr/local/bin', '/bin', '/usr/bin'] |
Note that SCons does allow you to define
the directories in the PATH
in a string,
separated by the pathname-separator character
for your system (':' on POSIX systems, ';' on Windows):
env['ENV']['PATH'] = '/usr/local/bin:/bin:/usr/bin' |
But doing so makes your SConscript file less portable, (although in this case that may not be a huge concern since the directories you list are likley system-specific, anyway).
PATH
From the External Environment
You may want to propagate the external PATH
to the execution environment for commands.
You do this by initializing the PATH
variable with the PATH
value from
the os.environ
dictionary,
which is Python's way of letting you
get at the external environment:
import os env = Environment(ENV = {'PATH' : os.environ['PATH']}) |
Alternatively, you may find it easier
to just propagate the entire external
environment to the execution environment
for commands.
This is simpler to code than explicity
selecting the PATH
value:
import os env = Environment(ENV = os.environ) |
Either of these will guarantee that
SCons will be able to execute
any command that you can execute from the command line.
The drawback is that the build can behave
differently if it's run by people with
different PATH
values in their environment--for example,
if both the /bin and
/usr/local/bin directories
have different cc commands,
then which one will be used to compile programs
will depend on which directory is listed
first in the user's PATH
variable.
PATH
Values in the Execution Environment
One of the most common requirements
for manipulating a variable in the execution environment
is to add one or more custom directories to a search
like the $PATH
variable on Linux or POSIX systems,
or the %PATH%
variable on Windows,
so that a locally-installed compiler or other utility
can be found when SCons tries to execute it to update a target.
SCons provides PrependENVPath and AppendENVPath functions
to make adding things to execution variables convenient.
You call these functions by specifying the variable
to which you want the value added,
and then value itself.
So to add some /usr/local directories
to the $PATH
and $LIB
variables,
you might:
env = Environment(ENV = os.environ) env.PrependENVPath('PATH', '/usr/local/bin') env.AppendENVPath('LIB', '/usr/local/lib') |
Note that the added values are strings,
and if you want to add multiple directories to
a variable like $PATH
,
you must include the path separate character
(: on Linux or POSIX,
; on Windows)
in the string.
SCons construction environments have a MergeFlags method that merges a dictionary of values into the construction environment. MergeFlags treats each value in the dictionary as a list of options such as one might pass to a command (such as a compiler or linker). MergeFlags will not duplicate an option if it already exists in the construction environment variable.
MergeFlags tries to be intelligent about merging options.
When merging options to any variable
whose name ends in PATH
,
MergeFlags keeps the leftmost occurrence of the option,
because in typical lists of directory paths,
the first occurrence "wins."
When merging options to any other variable name,
MergeFlags keeps the rightmost occurrence of the option,
because in a list of typical command-line options,
the last occurrence "wins."
env = Environment() env.Append(CCFLAGS = '-option -O3 -O1') flags = { 'CCFLAGS' : '-whatever -O3' } env.MergeFlags(flags) print env['CCFLAGS'] |
% scons -Q ['-option', '-O1', '-whatever', '-O3'] scons: `.' is up to date. |
Note that the default value for $CCFLAGS
is an internal SCons object
which automatically converts
the options we specified as a string into a list.
env = Environment() env.Append(CPPPATH = ['/include', '/usr/local/include', '/usr/include']) flags = { 'CPPPATH' : ['/usr/opt/include', '/usr/local/include'] } env.MergeFlags(flags) print env['CPPPATH'] |
% scons -Q ['/include', '/usr/local/include', '/usr/include', '/usr/opt/include'] scons: `.' is up to date. |
Note that the default value for $CPPPATH
is a normal Python list,
so we must specify its values as a list
in the dictionary we pass to the MergeFlags function.
If MergeFlags is passed anything other than a dictionary, it calls the ParseFlags method to convert it into a dictionary.
env = Environment() env.Append(CCFLAGS = '-option -O3 -O1') env.Append(CPPPATH = ['/include', '/usr/local/include', '/usr/include']) env.MergeFlags('-whatever -I/usr/opt/include -O3 -I/usr/local/include') print env['CCFLAGS'] print env['CPPPATH'] |
% scons -Q ['-option', '-O1', '-whatever', '-O3'] ['/include', '/usr/local/include', '/usr/include', '/usr/opt/include'] scons: `.' is up to date. |
In the combined example above, ParseFlags has sorted the options into their corresponding variables and returned a dictionary for MergeFlags to apply to the construction variables in the specified construction environment.
SCons has a bewildering array of construction variables for different types of options when building programs. Sometimes you may not know exactly which variable should be used for a particular option.
SCons construction environments have a ParseFlags method that takes a set of typical command-line options and distrbutes them into the appropriate construction variables. Historically, it was created to support the ParseConfig method, so it focuses on options used by the GNU Compiler Collection (GCC) for the C and C++ toolchains.
ParseFlags returns a dictionary containing the options distributed into their respective construction variables. Normally, this dictionary would be passed to MergeFlags to merge the options into a construction environment, but the dictionary can be edited if desired to provide additional functionality. (Note that if the flags are not going to be edited, calling MergeFlags with the options directly will avoid an additional step.)
env = Environment() d = env.ParseFlags("-I/opt/include -L/opt/lib -lfoo") l = d.items() l.sort() for k,v in l: if v: print k, v env.MergeFlags(d) env.Program('f1.c') |
% scons -Q CPPPATH ['/opt/include'] LIBPATH ['/opt/lib'] LIBS ['foo'] cc -o f1.o -c -I/opt/include f1.c cc -o f1 f1.o -L/opt/lib -lfoo |
Note that if the options are limited to generic types like those above, they will be correctly translated for other platform types:
C:\>scons -Q CPPPATH ['/opt/include'] LIBPATH ['/opt/lib'] LIBS ['foo'] cl /Fof1.obj /c f1.c /nologo /I\opt\include link /nologo /OUT:f1.exe /LIBPATH:\opt\lib foo.lib f1.obj |
Since the assumption is that the flags are used for the GCC toolchain,
unrecognized flags are placed in $CCFLAGS
so they will be used for both C and C++ compiles:
env = Environment() d = env.ParseFlags("-whatever") l = d.items() l.sort() for k,v in l: if v: print k, v env.MergeFlags(d) env.Program('f1.c') |
% scons -Q CCFLAGS -whatever cc -o f1.o -c -whatever f1.c cc -o f1 f1.o |
ParseFlags will also accept a (recursive) list of strings as input; the list is flattened before the strings are processed:
env = Environment() d = env.ParseFlags(["-I/opt/include", ["-L/opt/lib", "-lfoo"]]) l = d.items() l.sort() for k,v in l: if v: print k, v env.MergeFlags(d) env.Program('f1.c') |
% scons -Q CPPPATH ['/opt/include'] LIBPATH ['/opt/lib'] LIBS ['foo'] cc -o f1.o -c -I/opt/include f1.c cc -o f1 f1.o -L/opt/lib -lfoo |
If a string begins with a "!" (an exclamation mark, often called a bang), the string is passed to the shell for execution. The output of the command is then parsed:
env = Environment() d = env.ParseFlags(["!echo -I/opt/include", "!echo -L/opt/lib", "-lfoo"]) l = d.items() l.sort() for k,v in l: if v: print k, v env.MergeFlags(d) env.Program('f1.c') |
% scons -Q CPPPATH ['/opt/include'] LIBPATH ['/opt/lib'] LIBS ['foo'] cc -o f1.o -c -I/opt/include f1.c cc -o f1 f1.o -L/opt/lib -lfoo |
ParseFlags is regularly updated for new options; consult the man page for details about those currently recognized.
Configuring the right options to build programs to work with libraries--especially shared libraries--that are available on POSIX systems can be very complicated. To help this situation, various utilies with names that end in config return the command-line options for the GNU Compiler Collection (GCC) that are needed to use these libraries; for example, the command-line options to use a library named lib would be found by calling a utility named lib-config.
A more recent convention is that these options are available from the generic pkg-config program, which has common framework, error handling, and the like, so that all the package creator has to do is provide the set of strings for his particular package.
SCons construction environments have a ParseConfig method that executes a *config utility (either pkg-config or a more specific utility) and configures the appropriate construction variables in the environment based on the command-line options returned by the specified command.
env = Environment() env['CPPPATH'] = ['/lib/compat'] env.ParseConfig("pkg-config x11 --cflags --libs") print env['CPPPATH'] |
SCons will execute the specified command string, parse the resultant flags, and add the flags to the appropriate environment variables.
% scons -Q ['/lib/compat', '/usr/X11/include'] scons: `.' is up to date. |
In the example above, SCons has added the include directory to
CPPPATH
.
(Depending upon what other flags are emitted by the
pkg-config command,
other variables may have been extended as well.)
Note that the options are merged with existing options using the MergeFlags method, so that each option only occurs once in the construction variable:
env = Environment() env.ParseConfig("pkg-config x11 --cflags --libs") env.ParseConfig("pkg-config x11 --cflags --libs") print env['CPPPATH'] |
% scons -Q ['/usr/X11/include'] scons: `.' is up to date. |
A key aspect of creating a usable build configuration is providing good output from the build so its users can readily understand what the build is doing and get information about how to control the build. SCons provides several ways of controlling output from the build configuration to help make the build more useful and understandable.
It's often very useful to be able to give users some help that describes the specific targets, build options, etc., that can be used for your build. SCons provides the Help function to allow you to specify this help text:
Help(""" Type: 'scons program' to build the production program, 'scons debug' to build the debug version. """) |
(Note the above use of the Python triple-quote syntax, which comes in very handy for specifying multi-line strings like help text.)
When the SConstruct or SConscript files contain such a call to the Help function, the specified help text will be displayed in response to the SCons -h option:
% scons -h scons: Reading SConscript files ... scons: done reading SConscript files. Type: 'scons program' to build the production program, 'scons debug' to build the debug version. Use scons -H for help about command-line options. |
The SConscript files may contain multiple calls to the Help function, in which case the specified text(s) will be concatenated when displayed. This allows you to split up the help text across multiple SConscript files. In this situation, the order in which the SConscript files are called will determine the order in which the Help functions are called, which will determine the order in which the various bits of text will get concatenated.
Another use would be to make the help text conditional on some variable. For example, suppose you only want to display a line about building a Windows-only version of a program when actually run on Windows. The following SConstruct file:
env = Environment() Help("\nType: 'scons program' to build the production program.\n") if env['PLATFORM'] == 'win32': Help("\nType: 'scons windebug' to build the Windows debug version.\n") |
Will display the complete help text on Windows:
C:\>scons -h scons: Reading SConscript files ... scons: done reading SConscript files. Type: 'scons program' to build the production program. Type: 'scons windebug' to build the Windows debug version. Use scons -H for help about command-line options. |
But only show the relevant option on a Linux or UNIX system:
% scons -h scons: Reading SConscript files ... scons: done reading SConscript files. Type: 'scons program' to build the production program. Use scons -H for help about command-line options. |
If there is no Help text in the SConstruct or SConscript files, SCons will revert to displaying its standard list that describes the SCons command-line options. This list is also always displayed whenever the -H option is used.
$*COMSTR
Variables
Sometimes the commands executed
to compile object files or link programs
(or build other targets)
can get very long,
long enough to make it difficult for users
to distinguish error messages or
other important build output
from the commands themselves.
All of the default $*COM
variables
that specify the command lines
used to build various types of target files
have a corresponding $*COMSTR
variable
that can be set to an alternative
string that will be displayed
when the target is built.
For example, suppose you want to have SCons display a "Compiling" message whenever it's compiling an object file, and a "Linking" when it's linking an executable. You could write a SConstruct file that looks like:
env = Environment(CCCOMSTR = "Compiling $TARGET", LINKCOMSTR = "Linking $TARGET") env.Program('foo.c') |
Which would then yield the output:
% scons -Q Compiling foo.o Linking foo |
SCons performs complete variable substitution
on $*COMSTR
variables,
so they have access to all of the
standard variables like $TARGET
$SOURCES
, etc.,
as well as any construction variables
that happen to be configured in
the construction environment
used to build a specific target.
Of course, sometimes it's still important to be able to see the exact command that SCons will execute to build a target. For example, you may simply need to verify that SCons is configured to supply the right options to the compiler, or a developer may want to cut-and-paste a comiloe command to add a few options for a custom test.
One common way to give users
control over whether or not
SCons should print the actual command line
or a short, configured summary
is to add support for a
VERBOSE
command-line variable to your SConstruct file.
A simple configuration for this might look like:
env = Environment() if ARGUMENTS.get('VERBOSE') != "1': env['CCCOMSTR'] = "Compiling $TARGET" env['LINKCOMSTR'] = "Linking $TARGET" env.Program('foo.c') |
By only setting the appropriate
$*COMSTR
variables
if the user specifies
VERBOSE=1
on the command line,
the user has control
over how SCons
displays these particular command lines:
% scons -Q Compiling foo.o Linking foo % scons -Q -c Removed foo.o Removed foo % scons -Q VERBOSE=1 cc -o foo.o -c foo.c cc -o foo foo.o |
Another aspect of providing good build output is to give the user feedback about what SCons is doing even when nothing is being built at the moment. This can be especially true for large builds when most of the targets are already up-to-date. Because SCons can take a long time making absolutely sure that every target is, in fact, up-to-date with respect to a lot of dependency files, it can be easy for users to mistakenly conclude that SCons is hung or that there is some other problem with the build.
One way to deal with this perception is to configure SCons to print something to let the user know what it's "thinking about." The Progress function allows you to specify a string that will be printed for every file that SCons is "considering" while it is traversing the dependency graph to decide what targets are or are not up-to-date.
Progress('Evaluating $TARGET\n') Program('f1.c') Program('f2.c') |
Note that the Progress function does not arrange for a newline to be printed automatically at the end of the string (as does the Python print statement), and we must specify the \n that we want printed at the end of the configured string. This configuration, then, will have SCons print that it is Evaluating each file that it encounters in turn as it traverses the dependency graph:
% scons -Q Evaluating SConstruct Evaluating f1.c Evaluating f1.o cc -o f1.o -c f1.c Evaluating f1 cc -o f1 f1.o Evaluating f2.c Evaluating f2.o cc -o f2.o -c f2.c Evaluating f2 cc -o f2 f2.o Evaluating . |
Of course, normally you don't want to add all of these additional lines to your build output, as that can make it difficult for the user to find errors or other important messages. A more useful way to display this progress might be to have the file names printed directly to the user's screen, not to the same standard output stream where build output is printed, and to use a carriage return character (\r) so that each file name gets re-printed on the same line. Such a configuration would look like:
Progress('$TARGET\r', file=open('/dev/tty', 'w'), overwrite=True) Program('f1.c') Program('f2.c') |
Note that we also specified the overwrite=True argument to the Progress function, which causes SCons to "wipe out" the previous string with space characters before printing the next Progress string. Without the overwrite=True argument, a shorter file name would not overwrite all of the charactes in a longer file name that precedes it, making it difficult to tell what the actual file name is on the output. Also note that we opened up the /dev/tty file for direct access (on POSIX) to the user's screen. On Windows, the equivalent would be to open the con: file name.
Also, it's important to know that although you can use $TARGET to substitute the name of the node in the string, the Progress function does not perform general variable substitution (because there's not necessarily a construction environment involved in evaluating a node like a source file, for example).
You can also specify a list of strings to the Progress function, in which case SCons will display each string in turn. This can be used to implement a "spinner" by having SCons cycle through a sequence of strings:
Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5) Program('f1.c') Program('f2.c') |
Note that here we have also used the interval= keyword argument to have SCons only print a new "spinner" string once every five evaluated nodes. Using an interval= count, even with strings that use $TARGET like our examples above, can be a good way to lessen the work that SCons expends printing Progress strings, while still giving the user feedback that indicates SCons is still working on evaluating the build.
Lastly, you can have direct control over how to print each evaluated node by passing a Python function (or other Python callable) to the Progress function. Your function will be called for each evaluated node, allowing you to implement more sophisticated logic like adding a counter:
screen = open('/dev/tty', 'w') count = 0 def progress_function(node) count += 1 screen.write('Node %4d: %s\r' % (count, node)) Progress(progress_function) |
Of course, if you choose,
you could completely ignore the
node
argument to the function,
and just print a count,
or anything else you wish.
(Note that there's an obvious follow-on question here: how would you find the total number of nodes that will be evaluated so you can tell the user how close the build is to finishing? Unfortunately, in the general case, there isn't a good way to do that, short of having SCons evaluate its dependency graph twice, first to count the total and the second time to actually build the targets. This would be necessary because you can't know in advance which target(s) the user actually requested to be built. The entire build may consist of thousands of Nodes, for example, but maybe the user specifically requested that only a single object file be built.)
SCons, like most build tools, returns zero status to the shell on success and nonzero status on failure. Sometimes it's useful to give more information about the build status at the end of the run, for instance to print an informative message, send an email, or page the poor slob who broke the build.
SCons provides a GetBuildFailures method that you can use in a python atexit function to get a list of objects describing the actions that failed while attempting to build targets. There can be more than one if you're using -j. Here's a simple example:
import atexit def print_build_failures(): from SCons.Script import GetBuildFailures for bf in GetBuildFailures(): print "%s failed: %s" % (bf.node, bf.errstr) atexit.register(print_build_failures) |
The atexit.register call registers print_build_failures as an atexit callback, to be called before SCons exits. When that function is called, it calls GetBuildFailures to fetch the list of failed objects. See the man page for the detailed contents of the returned objects; some of the more useful attributes are .node, .errstr, .filename, and .command. The filename is not necessarily the same file as the node; the node is the target that was being built when the error occurred, while the filenameis the file or dir that actually caused the error. Note: only call GetBuildFailures at the end of the build; calling it at any other time is undefined.
Here is a more complete example showing how to turn each element of GetBuildFailures into a string:
# Make the build fail if we pass fail=1 on the command line if ARGUMENTS.get('fail', 0): Command('target', 'source', ['/bin/false']) def bf_to_str(bf): """Convert an element of GetBuildFailures() to a string in a useful way.""" import SCons.Errors if bf is None: # unknown targets product None in list return '(unknown tgt)' elif isinstance(bf, SCons.Errors.StopError): return str(bf) elif bf.node: return str(bf.node) + ': ' + bf.errstr elif bf.filename: return bf.filename + ': ' + bf.errstr return 'unknown failure: ' + bf.errstr import atexit def build_status(): """Convert the build status to a 2-tuple, (status, msg).""" from SCons.Script import GetBuildFailures bf = GetBuildFailures() if bf: # bf is normally a list of build failures; if an element is None, # it's because of a target that scons doesn't know anything about. status = 'failed' failures_message = "\n".join(["Failed building %s" % bf_to_str(x) for x in bf if x is not None]) else: # if bf is None, the build completed successfully. status = 'ok' failures_message = '' return (status, failures_message) def display_build_status(): """Display the build status. Called by atexit. Here you could do all kinds of complicated things.""" status, failures_message = build_status() if status == 'failed': print "FAILED!!!!" # could display alert, ring bell, etc. elif status == 'ok': print "Build succeeded." print failures_message atexit.register(display_build_status) |
When this runs, you'll see the appropriate output:
% scons -Q scons: `.' is up to date. Build succeeded. % scons -Q fail=1 scons: *** Source `source' not found, needed by target `target'. Stop. FAILED!!!! Failed building Source `source' not found, needed by target `target'. |
SCons provides a number of ways for the writer of the SConscript files to give the users who will run SCons a great deal of control over the build execution. The arguments that the user can specify on the command line are broken down into three types:
Command-line options always begin with one or two - (hyphen) characters. SCons provides ways for you to examind and set options values from within your SConscript files, as well as the ability to define your own custom options. See the Section called Command-Line Options, below.
Any command-line argument containing an =
(equal sign) is considered a variable setting with the form
variable
=value
SCons provides direct access to
all of the command-line variable settings,
the ability to apply command-line variable settings
to construction environments,
and functions for configuring
specific types of variables
(Boolean values, path names, etc.)
with automatic validation of the user's specified values.
See the Section called Command-Line variable
=value
Build Variables, below.
Any command-line argument that is not an option or a variable setting (does not begin with a hyphen and does not contain an equal sign) is considered a target that the user (presumably) wants SCons to build. A list of Node objects representing the target or targets to build. SCons provides access to the list of specified targets, as well as ways to set the default list of targets from within the SConscript files. See the Section called Command-Line Targets, below.
SCons has many command-line options that control its behavior. A SCons command-line option always begins with one or two - (hyphen) characters.
SCONSFLAGS
Environment Variable
Users may find themselves supplying
the same command-line options every time
they run SCons.
For example, you might find it saves time
to specify a value of -j 2
to have SCons run up to two build commands in parallel.
To avoid having to type -j 2 by hand
every time,
you can set the external environment variable
SCONSFLAGS
to a string containing
command-line options that you want SCons to use.
If, for example,
you're using a POSIX shell that's
compatible with the Bourne shell,
and you always want SCons to use the
-Q option,
you can set the SCONSFLAGS
environment as follows:
% scons scons: Reading SConscript files ... scons: done reading SConscript files. scons: Building targets ... ... [build output] ... scons: done building targets. % export SCONSFLAGS="-Q" % scons ... [build output] ... |
Users of csh-style shells on POSIX systems
can set the SCONSFLAGS
environment as follows:
$ setenv SCONSFLAGS "-Q" |
Windows users may typically want to set the
SCONSFLAGS
in the appropriate tab of the
System Properties window.
SCons provides the GetOption function to get the values set by the various command-line options. One common use of this is to check whether or not the -h or --help option has been specified. Normally, SCons does not print its help text until after it has read all of the SConscript files, because it's possible that help text has been added by some subsidiary SConscript file deep in the source tree hierarchy. Of course, reading all of the SConscript files takes extra time.
If you know that your configuration does not define any additional help text in subsidiary SConscript files, you can speed up the command-line help available to users by using the GetOption function to load the subsidiary SConscript files only if the the user has not specified the -h or --help option, like so:
In general, the string that you pass to the GetOption function to fetch the value of a command-line option setting is the same as the "most common" long option name (beginning with two hyphen characters), although there are some exceptions. The list of SCons command-line options and the GetOption strings for fetching them, are available in the the Section called Strings for Getting or Setting Values of SCons Command-Line Options section, below.
You can also set the values of SCons command-line options from within the SConscript files by using the SetOption function. The strings that you use to set the values of SCons command-line options are available in the the Section called Strings for Getting or Setting Values of SCons Command-Line Options section, below.
One use of the SetOption function is to specify a value for the -j or --jobs option, so that users get the improved performance of a parallel build without having to specify the option by hand. A complicating factor is that a good value for the -j option is somewhat system-dependent. One rough guideline is that the more processors your system has, the higher you want to set the -j value, in order to take advantage of the number of CPUs.
For example, suppose the administrators
of your development systems
have standardized on setting a
NUM_CPU
environment variable
to the number of processors on each system.
A little bit of Python code
to access the environment variable
and the SetOption function
provide the right level of flexibility:
import os num_cpu = int(os.environ.get('NUM_CPU', 2)) SetOption('num_jobs', num_cpu) print "running with -j", GetOption('num_jobs') |
The above snippet of code
sets the value of the --jobs option
to the value specified in the
$NUM_CPU
environment variable.
(This is one of the exception cases
where the string is spelled differently from
the from command-line option.
The string for fetching or setting the --jobs
value is num_jobs
for historical reasons.)
The code in this example prints the num_jobs
value for illustrative purposes.
It uses a default value of 2
to provide some minimal parallelism even on
single-processor systems:
% scons -Q running with -j 2 scons: `.' is up to date. |
But if the $NUM_CPU
environment variable is set,
then we use that for the default number of jobs:
% export NUM_CPU="4" % scons -Q running with -j 4 scons: `.' is up to date. |
But any explicit
-j or --jobs
value the user specifies an the command line is used first,
regardless of whether or not
the $NUM_CPU
environment
variable is set:
% scons -Q -j 7 running with -j 7 scons: `.' is up to date. % export NUM_CPU="4" % scons -Q -j 3 running with -j 3 scons: `.' is up to date. |
The strings that you can pass to the GetOption and SetOption functions usually correspond to the first long-form option name (beginning with two hyphen characters: --), after replacing any remaining hyphen characters with underscores.
The full list of strings and the variables they correspond to is as follows:
String for GetOption and SetOption | Command-Line Option(s) |
---|---|
cache_debug | --cache-debug |
cache_disable | --cache-disable |
cache_force | --cache-force |
cache_show | --cache-show |
clean | -c ,
--clean ,
--remove |
config | --config |
directory | -C ,
--directory |
diskcheck | --diskcheck |
duplicate | --duplicate |
file | -f ,
--file ,
--makefile ,
--sconstruct |
help | -h ,
--help |
ignore_errors | --ignore-errors |
implicit_cache | --implicit-cache |
implicit_deps_changed | --implicit-deps-changed |
implicit_deps_unchanged | --implicit-deps-unchanged |
interactive | --interact ,
--interactive |
keep_going | -k ,
--keep-going |
max_drift | --max-drift |
no_exec | -n ,
--no-exec ,
--just-print ,
--dry-run ,
--recon |
no_site_dir | --no-site-dir |
num_jobs | -j ,
--jobs |
profile_file | --profile |
question | -q ,
--question |
random | --random |
repository | -Y ,
--repository ,
--srcdir |
silent | -s ,
--silent ,
--quiet |
site_dir | --site-dir |
stack_size | --stack-size |
taskmastertrace_file | --taskmastertrace |
warn | --warn --warning |
SCons also allows you to define your own command-line options with the AddOption function. The AddOption function takes the same arguments as the optparse.add_option function from the standard Python library. [3] Once you have added a custom command-line option with the AddOption function, the value of the option (if any) is immediately available using the standard GetOption function. (The value can also be set using SetOption, although that's not very useful in practice because a default value can be specified in directly in the AddOption call.)
One useful example of using this functionality
is to provide a --prefix
for users:
AddOption('--prefix', dest='prefix', type='string', nargs=1, action='store', metavar='DIR', help='installation prefix') env = Environment(PREFIX = GetOption('prefix')) installed_foo = env.Install('$PREFIX/usr/bin', 'foo.in') Default(installed_foo) |
The above code uses the GetOption function
to set the $PREFIX
construction variable to any
value that the user specifies with a command-line
option of --prefix.
Because $PREFIX
will expand to a null string if it's not initialized,
running SCons without the
option of --prefix
will install the file in the
/usr/bin/ directory:
% scons -Q -n Install file: "foo.in" as "/usr/bin/foo.in" |
But specifying --prefix=/tmp/install on the command line causes the file to be installed in the /tmp/install/usr/bin/ directory:
% scons -Q -n --prefix=/tmp/install Install file: "foo.in" as "/tmp/install/usr/bin/foo.in" |
variable
=value
Build Variables
You may want to control various aspects
of your build by allowing the user
to specify variable
=value
values on the command line.
For example, suppose you
want users to be able to
build a debug version of a program
by running SCons as follows:
% scons -Q debug=1 |
SCons provides an ARGUMENTS
dictionary
that stores all of the
variable
=value
assignments from the command line.
This allows you to modify
aspects of your build in response
to specifications on the command line.
(Note that unless you want to require
that users always
specify a variable,
you probably want to use
the Python
ARGUMENTS.get() function,
which allows you to specify a default value
to be used if there is no specification
on the command line.)
The following code sets the $CCFLAGS
construction
variable in response to the debug
flag being set in the ARGUMENTS
dictionary:
env = Environment() debug = ARGUMENTS.get('debug', 0) if int(debug): env.Append(CCFLAGS = '-g') env.Program('prog.c') |
This results in the -g
compiler option being used when
debug=1
is used on the command line:
% scons -Q debug=0 cc -o prog.o -c prog.c cc -o prog prog.o % scons -Q debug=0 scons: `.' is up to date. % scons -Q debug=1 cc -o prog.o -c -g prog.c cc -o prog prog.o % scons -Q debug=1 scons: `.' is up to date. |
Notice that SCons keeps track of the last values used to build the object files, and as a result correctly rebuilds the object and executable files only when the value of the debug argument has changed.
The ARGUMENTS
dictionary has two minor drawbacks.
First, because it is a dictionary,
it can only store one value for each specified keyword,
and thus only "remembers" the last setting
for each keyword on the command line.
This makes the ARGUMENTS
dictionary
inappropriate if users should be able to
specify multiple values
on the command line for a given keyword.
Second, it does not preserve
the order in which the variable settings
were specified,
which is a problem if
you want the configuration to
behave differently in response
to the order in which the build
variable settings were specified on the command line.
To accomodate these requirements,
SCons provides an ARGLIST
variable
that gives you direct access to
variable
=value
settings on the command line,
in the exact order they were specified,
and without removing any duplicate settings.
Each element in the ARGLIST
variable
is itself a two-element list
containing the keyword and the value
of the setting,
and you must loop through,
or otherwise select from,
the elements of ARGLIST
to
process the specific settings you want
in whatever way is appropriate for your configuration.
For example,
the following code to let the user
add to the CPPDEFINES
construction variable
by specifying multiple
define=
settings on the command line:
cppdefines = [] for key, value in ARGLIST: if key == 'define': cppdefines.append(value) env = Environment(CPPDEFINES = cppdefines) env.Object('prog.c') |
Yields the followig output:
% scons -Q define=FOO cc -o prog.o -c -DFOO prog.c % scons -Q define=FOO define=BAR cc -o prog.o -c -DFOO -DBAR prog.c |
Note that the ARGLIST
and ARGUMENTS
variables do not interfere with each other,
but merely provide slightly different views
into how the user specified
variable
=value
settings on the command line.
You can use both variables in the same
SCons configuration.
In general, the ARGUMENTS
dictionary
is more convenient to use,
(since you can just fetch variable
settings through a dictionary access),
and the ARGLIST
list
is more flexible
(since you can examine the
specific order in which
the user's command-line variabe settings).
Being able to use a command-line build variable like debug=1 is handy, but it can be a chore to write specific Python code to recognize each such variable, check for errors and provide appropriate messages, and apply the values to a construction variable. To help with this, SCons supports a class to define such build variables easily, and a mechanism to apply the build variables to a construction environment. This allows you to control how the build variables affect construction environments.
For example, suppose that you want users to set
a RELEASE
construction variable on the
command line whenever the time comes to build
a program for release,
and that the value of this variable
should be added to the command line
with the appropriate -D option
(or other command line option)
to pass the value to the C compiler.
Here's how you might do that by setting
the appropriate value in a dictionary for the
$CPPDEFINES
construction variable:
vars = Variables() vars.Add('RELEASE', 'Set to 1 to build for release', 0) env = Environment(variables = vars, CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'}) env.Program(['foo.c', 'bar.c']) |
This SConstruct file first creates a Variables object
(the vars = Variables() call),
and then uses the object's Add
method to indicate that the RELEASE
variable can be set on the command line,
and that its default value will be 0
(the third argument to the Add method).
The second argument is a line of help text;
we'll learn how to use it in the next section.
We then pass the created Variables
object as a variables
keyword argument
to the Environment call
used to create the construction environment.
This then allows a user to set the
RELEASE
build variable on the command line
and have the variable show up in
the command line used to build each object from
a C source file:
% scons -Q RELEASE=1 cc -o bar.o -c -DRELEASE_BUILD=1 bar.c cc -o foo.o -c -DRELEASE_BUILD=1 foo.c cc -o foo foo.o bar.o |
NOTE: Before SCons release 0.98.1, these build variables were known as "command-line build options." The class was actually named the Options class, and in the sections below, the various functions were named BoolOption, EnumOption, ListOption, PathOption, PackageOption and AddOptions. These older names still work, and you may encounter them in older SConscript fles, but their use is discouraged and will be officially deprecated some day.
To make command-line build variables most useful, you ideally want to provide some help text that will describe the available variables when the user runs scons -h. You could write this text by hand, but SCons provides an easier way. Variables objects support a GenerateHelpText method that will, as its name suggests, generate text that describes the various variables that have been added to it. You then pass the output from this method to the Help function:
vars = Variables('custom.py') vars.Add('RELEASE', 'Set to 1 to build for release', 0) env = Environment(variables = vars) Help(vars.GenerateHelpText(env)) |
SCons will now display some useful text when the -h option is used:
% scons -Q -h RELEASE: Set to 1 to build for release default: 0 actual: 0 Use scons -H for help about command-line options. |
Notice that the help output shows the default value, and the current actual value of the build variable.
Giving the user a way to specify the value of a build variable on the command line is useful, but can still be tedious if users must specify the variable every time they run SCons. We can let users provide customized build variable settings in a local file by providing a file name when we create the Variables object:
vars = Variables('custom.py') vars.Add('RELEASE', 'Set to 1 to build for release', 0) env = Environment(variables = vars, CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'}) env.Program(['foo.c', 'bar.c']) Help(vars.GenerateHelpText(env)) |
This then allows the user to control the RELEASE
variable by setting it in the custom.py file:
RELEASE = 1 |
Note that this file is actually executed like a Python script. Now when we run SCons:
% scons -Q cc -o bar.o -c -DRELEASE_BUILD=1 bar.c cc -o foo.o -c -DRELEASE_BUILD=1 foo.c cc -o foo foo.o bar.o |
And if we change the contents of custom.py to:
RELEASE = 0 |
The object files are rebuilt appropriately with the new variable:
% scons -Q cc -o bar.o -c -DRELEASE_BUILD=0 bar.c cc -o foo.o -c -DRELEASE_BUILD=0 foo.c cc -o foo foo.o bar.o |
SCons provides a number of functions that provide ready-made behaviors for various types of command-line build variables.
It's often handy to be able to specify a variable that controls a simple Boolean variable with a true or false value. It would be even more handy to accomodate users who have different preferences for how to represent true or false values. The BoolVariable function makes it easy to accomodate these common representations of true or false.
The BoolVariable function takes three arguments: the name of the build variable, the default value of the build variable, and the help string for the variable. It then returns appropriate information for passing to the Add method of a Variables object, like so:
vars = Variables('custom.py') vars.Add(BoolVariable('RELEASE', 'Set to build for release', 0)) env = Environment(variables = vars, CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'}) env.Program('foo.c') |
With this build variable,
the RELEASE
variable can now be enabled by
setting it to the value yes
or t:
% scons -Q RELEASE=yes foo.o cc -o foo.o -c -DRELEASE_BUILD=True foo.c |
% scons -Q RELEASE=t foo.o cc -o foo.o -c -DRELEASE_BUILD=True foo.c |
Other values that equate to true include y, 1, on and all.
Conversely, RELEASE
may now be given a false
value by setting it to
no
or
f:
% scons -Q RELEASE=no foo.o cc -o foo.o -c -DRELEASE_BUILD=False foo.c |
% scons -Q RELEASE=f foo.o cc -o foo.o -c -DRELEASE_BUILD=False foo.c |
Other values that equate to false include n, 0, off and none.
Lastly, if a user tries to specify any other value, SCons supplies an appropriate error message:
% scons -Q RELEASE=bad_value foo.o scons: *** Error converting option: RELEASE Invalid value for boolean option: bad_value File "/home/my/project/SConstruct", line 4, in <module> |
Suppose that we want a user to be able to
set a COLOR
variable
that selects a background color to be
displayed by an application,
but that we want to restrict the
choices to a specific set of allowed colors.
This can be set up quite easily
using the EnumVariable,
which takes a list of allowed_values
in addition to the variable name,
default value,
and help text arguments:
vars = Variables('custom.py') vars.Add(EnumVariable('COLOR', 'Set background color', 'red', allowed_values=('red', 'green', 'blue'))) env = Environment(variables = vars, CPPDEFINES={'COLOR' : '"${COLOR}"'}) env.Program('foo.c') |
The user can now explicity set the COLOR
build variable
to any of the specified allowed values:
% scons -Q COLOR=red foo.o cc -o foo.o -c -DCOLOR="red" foo.c % scons -Q COLOR=blue foo.o cc -o foo.o -c -DCOLOR="blue" foo.c % scons -Q COLOR=green foo.o cc -o foo.o -c -DCOLOR="green" foo.c |
But, almost more importantly,
an attempt to set COLOR
to a value that's not in the list
generates an error message:
% scons -Q COLOR=magenta foo.o scons: *** Invalid value for option COLOR: magenta File "/home/my/project/SConstruct", line 5, in <module> |
The EnumVariable function also supports a way
to map alternate names to allowed values.
Suppose, for example,
that we want to allow the user
to use the word navy as a synonym for
blue.
We do this by adding a map
dictionary
that will map its key values
to the desired legal value:
vars = Variables('custom.py') vars.Add(EnumVariable('COLOR', 'Set background color', 'red', allowed_values=('red', 'green', 'blue'), map={'navy':'blue'})) env = Environment(variables = vars, CPPDEFINES={'COLOR' : '"${COLOR}"'}) env.Program('foo.c') |
As desired, the user can then use
navy on the command line,
and SCons will translate it into blue
when it comes time to use the COLOR
variable to build a target:
% scons -Q COLOR=navy foo.o cc -o foo.o -c -DCOLOR="blue" foo.c |
By default, when using the EnumVariable function, arguments that differ from the legal values only in case are treated as illegal values:
% scons -Q COLOR=Red foo.o scons: *** Invalid value for option COLOR: Red File "/home/my/project/SConstruct", line 5, in <module> % scons -Q COLOR=BLUE foo.o scons: *** Invalid value for option COLOR: BLUE File "/home/my/project/SConstruct", line 5, in <module> % scons -Q COLOR=nAvY foo.o scons: *** Invalid value for option COLOR: nAvY File "/home/my/project/SConstruct", line 5, in <module> |
The EnumVariable function can take an additional
ignorecase
keyword argument that,
when set to 1,
tells SCons to allow case differences
when the values are specified:
vars = Variables('custom.py') vars.Add(EnumVariable('COLOR', 'Set background color', 'red', allowed_values=('red', 'green', 'blue'), map={'navy':'blue'}, ignorecase=1)) env = Environment(variables = vars, CPPDEFINES={'COLOR' : '"${COLOR}"'}) env.Program('foo.c') |
Which yields the output:
% scons -Q COLOR=Red foo.o cc -o foo.o -c -DCOLOR="Red" foo.c % scons -Q COLOR=BLUE foo.o cc -o foo.o -c -DCOLOR="BLUE" foo.c % scons -Q COLOR=nAvY foo.o cc -o foo.o -c -DCOLOR="blue" foo.c % scons -Q COLOR=green foo.o cc -o foo.o -c -DCOLOR="green" foo.c |
Notice that an ignorecase
value of 1
preserves the case-spelling that the user supplied.
If you want SCons to translate the names
into lower-case,
regardless of the case used by the user,
specify an ignorecase
value of 2:
vars = Variables('custom.py') vars.Add(EnumVariable('COLOR', 'Set background color', 'red', allowed_values=('red', 'green', 'blue'), map={'navy':'blue'}, ignorecase=2)) env = Environment(variables = vars, CPPDEFINES={'COLOR' : '"${COLOR}"'}) env.Program('foo.c') |
Now SCons will use values of red, green or blue regardless of how the user spells those values on the command line:
% scons -Q COLOR=Red foo.o cc -o foo.o -c -DCOLOR="red" foo.c % scons -Q COLOR=nAvY foo.o cc -o foo.o -c -DCOLOR="blue" foo.c % scons -Q COLOR=GREEN foo.o cc -o foo.o -c -DCOLOR="green" foo.c |
Another way in which you might want to allow users
to control a build variable is to
specify a list of one or more legal values.
SCons supports this through the ListVariable function.
If, for example, we want a user to be able to set a
COLORS
variable to one or more of the legal list of values:
vars = Variables('custom.py') vars.Add(ListVariable('COLORS', 'List of colors', 0, ['red', 'green', 'blue'])) env = Environment(variables = vars, CPPDEFINES={'COLORS' : '"${COLORS}"'}) env.Program('foo.c') |
A user can now specify a comma-separated list of legal values, which will get translated into a space-separated list for passing to the any build commands:
% scons -Q COLORS=red,blue foo.o cc -o foo.o -c -DCOLORS="red blue" foo.c % scons -Q COLORS=blue,green,red foo.o cc -o foo.o -c -DCOLORS="blue green red" foo.c |
In addition, the ListVariable function allows the user to specify explicit keywords of all or none to select all of the legal values, or none of them, respectively:
% scons -Q COLORS=all foo.o cc -o foo.o -c -DCOLORS="red green blue" foo.c % scons -Q COLORS=none foo.o cc -o foo.o -c -DCOLORS="" foo.c |
And, of course, an illegal value still generates an error message:
% scons -Q COLORS=magenta foo.o scons: *** Error converting option: COLORS Invalid value(s) for option: magenta File "/home/my/project/SConstruct", line 5, in <module> |
SCons supports a PathVariable function to make it easy to create a build variable to control an expected path name. If, for example, you need to define a variable in the preprocessor that controls the location of a configuration file:
vars = Variables('custom.py') vars.Add(PathVariable('CONFIG', 'Path to configuration file', '/etc/my_config')) env = Environment(variables = vars, CPPDEFINES={'CONFIG_FILE' : '"$CONFIG"'}) env.Program('foo.c') |
This then allows the user to
override the CONFIG
build variable
on the command line as necessary:
% scons -Q foo.o cc -o foo.o -c -DCONFIG_FILE="/etc/my_config" foo.c % scons -Q CONFIG=/usr/local/etc/other_config foo.o scons: `foo.o' is up to date. |
By default, PathVariable checks to make sure that the specified path exists and generates an error if it doesn't:
% scons -Q CONFIG=/does/not/exist foo.o scons: *** Path for option CONFIG does not exist: /does/not/exist File "/home/my/project/SConstruct", line 6, in <module> |
PathVariable provides a number of methods that you can use to change this behavior. If you want to ensure that any specified paths are, in fact, files and not directories, use the PathVariable.PathIsFile method:
vars = Variables('custom.py') vars.Add(PathVariable('CONFIG', 'Path to configuration file', '/etc/my_config', PathVariable.PathIsFile)) env = Environment(variables = vars, CPPDEFINES={'CONFIG_FILE' : '"$CONFIG"'}) env.Program('foo.c') |
Conversely, to ensure that any specified paths are directories and not files, use the PathVariable.PathIsDir method:
vars = Variables('custom.py') vars.Add(PathVariable('DBDIR', 'Path to database directory', '/var/my_dbdir', PathVariable.PathIsDir)) env = Environment(variables = vars, CPPDEFINES={'DBDIR' : '"$DBDIR"'}) env.Program('foo.c') |
If you want to make sure that any specified paths are directories, and you would like the directory created if it doesn't already exist, use the PathVariable.PathIsDirCreate method:
vars = Variables('custom.py') vars.Add(PathVariable('DBDIR', 'Path to database directory', '/var/my_dbdir', PathVariable.PathIsDirCreate)) env = Environment(variables = vars, CPPDEFINES={'DBDIR' : '"$DBDIR"'}) env.Program('foo.c') |
Lastly, if you don't care whether the path exists, is a file, or a directory, use the PathVariable.PathAccept method to accept any path that the user supplies:
vars = Variables('custom.py') vars.Add(PathVariable('OUTPUT', 'Path to output file or directory', None, PathVariable.PathAccept)) env = Environment(variables = vars, CPPDEFINES={'OUTPUT' : '"$OUTPUT"'}) env.Program('foo.c') |
Sometimes you want to give users even more control over a path name variable, allowing them to explicitly enable or disable the path name by using yes or no keywords, in addition to allow them to supply an explicit path name. SCons supports the PackageVariable function to support this:
vars = Variables('custom.py') vars.Add(PackageVariable('PACKAGE', 'Location package', '/opt/location')) env = Environment(variables = vars, CPPDEFINES={'PACKAGE' : '"$PACKAGE"'}) env.Program('foo.c') |
When the SConscript file uses the PackageVariable funciton, user can now still use the default or supply an overriding path name, but can now explicitly set the specified variable to a value that indicates the package should be enabled (in which case the default should be used) or disabled:
% scons -Q foo.o cc -o foo.o -c -DPACKAGE="/opt/location" foo.c % scons -Q PACKAGE=/usr/local/location foo.o cc -o foo.o -c -DPACKAGE="/usr/local/location" foo.c % scons -Q PACKAGE=yes foo.o cc -o foo.o -c -DPACKAGE="True" foo.c % scons -Q PACKAGE=no foo.o cc -o foo.o -c -DPACKAGE="False" foo.c |
Lastly, SCons provides a way to add multiple build variables to a Variables object at once. Instead of having to call the Add method multiple times, you can call the AddVariables method with a list of build variables to be added to the object. Each build variable is specified as either a tuple of arguments, just like you'd pass to the Add method itself, or as a call to one of the pre-defined functions for pre-packaged command-line build variables. in any order:
vars = Variables() vars.AddVariables( ('RELEASE', 'Set to 1 to build for release', 0), ('CONFIG', 'Configuration file', '/etc/my_config'), BoolVariable('warnings', 'compilation with -Wall and similiar', 1), EnumVariable('debug', 'debug output and symbols', 'no', allowed_values=('yes', 'no', 'full'), map={}, ignorecase=0), # case sensitive ListVariable('shared', 'libraries to build as shared libraries', 'all', names = list_of_libs), PackageVariable('x11', 'use X11 installed here (yes = search some places)', 'yes'), PathVariable('qtdir', 'where the root of Qt is installed', qtdir), ) |
Users may, of course,
occasionally misspell variable names in their command-line settings.
SCons does not generate an error or warning
for any unknown variables the users specifies on the command line.
(This is in no small part because you may be
processing the arguments directly using the ARGUMENTS
dictionary,
and therefore SCons can't know in the general case
whether a given "misspelled" variable is
really unknown and a potential problem,
or something that your SConscript file
will handle directly with some Python code.)
If, however, you're using a Variables object to define a specific set of command-line build variables that you expect users to be able to set, you may want to provide an error message or warning of your own if the user supplies a variable setting that is not among the defined list of variable names known to the Variables object. You can do this by calling the UnknownVariables method of the Variables object:
vars = Variables(None) vars.Add('RELEASE', 'Set to 1 to build for release', 0) env = Environment(variables = vars, CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'}) unknown = vars.UnknownVariables() if unknown: print "Unknown variables:", unknown.keys() Exit(1) env.Program('foo.c') |
The UnknownVariables method returns a dictionary containing the keywords and values of any variables the user specified on the command line that are not among the variables known to the Variables object (from having been specified using the Variables object'sAdd method). In the examble above, we check for whether the dictionary returned by the UnknownVariables is non-empty, and if so print the Python list containing the names of the unknwown variables and then call the Exit function to terminate SCons:
% scons -Q NOT_KNOWN=foo Unknown variables: ['NOT_KNOWN'] |
Of course, you can process the items in the dictionary returned by the UnknownVariables function in any way appropriate to your bulid configuration, including just printing a warning message but not exiting, logging an error somewhere, etc.
Note that you must delay the call of UnknownVariables until after you have applied the Variables object to a construction environment with the variables= keyword argument of an Environment call.
COMMAND_LINE_TARGETS
Variable
SCons supports a COMMAND_LINE_TARGETS
variable
that lets you fetch the list of targets that the
user specified on the command line.
You can use the targets to manipulate the
build in any way you wish.
As a simple example,
suppose that you want to print a reminder
to the user whenever a specific program is built.
You can do this by checking for the
target in the COMMAND_LINE_TARGETS
list:
if 'bar' in COMMAND_LINE_TARGETS: print "Don't forget to copy `bar' to the archive!" Default(Program('foo.c')) Program('bar.c') |
Then, running SCons with the default target works as it always does, but explicity specifying the bar target on the command line generates the warning message:
% scons -Q cc -o foo.o -c foo.c cc -o foo foo.o % scons -Q bar Don't forget to copy `bar' to the archive! cc -o bar.o -c bar.c cc -o bar bar.o |
Another practical use for the COMMAND_LINE_TARGETS
variable
might be to speed up a build
by only reading certain subsidiary SConscript
files if a specific target is requested.
One of the most basic things you can control is which targets SCons will build by default--that is, when there are no targets specified on the command line. As mentioned previously, SCons will normally build every target in or below the current directory by default--that is, when you don't explicitly specify one or more targets on the command line. Sometimes, however, you may want to specify explicitly that only certain programs, or programs in certain directories, should be built by default. You do this with the Default function:
env = Environment() hello = env.Program('hello.c') env.Program('goodbye.c') Default(hello) |
This SConstruct file knows how to build two programs, hello and goodbye, but only builds the hello program by default:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q scons: `hello' is up to date. % scons -Q goodbye cc -o goodbye.o -c goodbye.c cc -o goodbye goodbye.o |
Note that, even when you use the Default function in your SConstruct file, you can still explicitly specify the current directory (.) on the command line to tell SCons to build everything in (or below) the current directory:
% scons -Q . cc -o goodbye.o -c goodbye.c cc -o goodbye goodbye.o cc -o hello.o -c hello.c cc -o hello hello.o |
You can also call the Default function more than once, in which case each call adds to the list of targets to be built by default:
env = Environment() prog1 = env.Program('prog1.c') Default(prog1) prog2 = env.Program('prog2.c') prog3 = env.Program('prog3.c') Default(prog3) |
Or you can specify more than one target in a single call to the Default function:
env = Environment() prog1 = env.Program('prog1.c') prog2 = env.Program('prog2.c') prog3 = env.Program('prog3.c') Default(prog1, prog3) |
Either of these last two examples will build only the prog1 and prog3 programs by default:
% scons -Q cc -o prog1.o -c prog1.c cc -o prog1 prog1.o cc -o prog3.o -c prog3.c cc -o prog3 prog3.o % scons -Q . cc -o prog2.o -c prog2.c cc -o prog2 prog2.o |
You can list a directory as an argument to Default:
env = Environment() env.Program(['prog1/main.c', 'prog1/foo.c']) env.Program(['prog2/main.c', 'prog2/bar.c']) Default('prog1') |
In which case only the target(s) in that directory will be built by default:
% scons -Q cc -o prog1/foo.o -c prog1/foo.c cc -o prog1/main.o -c prog1/main.c cc -o prog1/main prog1/main.o prog1/foo.o % scons -Q scons: `prog1' is up to date. % scons -Q . cc -o prog2/bar.o -c prog2/bar.c cc -o prog2/main.o -c prog2/main.c cc -o prog2/main prog2/main.o prog2/bar.o |
Lastly, if for some reason you don't want any targets built by default, you can use the Python None variable:
env = Environment() prog1 = env.Program('prog1.c') prog2 = env.Program('prog2.c') Default(None) |
Which would produce build output like:
% scons -Q scons: *** No targets specified and no Default() targets found. Stop. % scons -Q . cc -o prog1.o -c prog1.c cc -o prog1 prog1.o cc -o prog2.o -c prog2.c cc -o prog2 prog2.o |
DEFAULT_TARGETS
Variable
SCons supports a DEFAULT_TARGETS
variable
that lets you get at the current list of default targets.
The DEFAULT_TARGETS
variable has
two important differences from the COMMAND_LINE_TARGETS
variable.
First, the DEFAULT_TARGETS
variable is a list of
internal SCons nodes,
so you need to convert the list elements to strings
if you want to print them or look for a specific target name.
Fortunately, you can do this easily
by using the Python map function
to run the list through str:
prog1 = Program('prog1.c') Default(prog1) print "DEFAULT_TARGETS is", map(str, DEFAULT_TARGETS) |
(Keep in mind that all of the manipulation of the
DEFAULT_TARGETS
list takes place during the
first phase when SCons is reading up the SConscript files,
which is obvious if
we leave off the -Q flag when we run SCons:)
% scons scons: Reading SConscript files ... DEFAULT_TARGETS is ['prog1'] scons: done reading SConscript files. scons: Building targets ... cc -o prog1.o -c prog1.c cc -o prog1 prog1.o scons: done building targets. |
Second,
the contents of the DEFAULT_TARGETS
list change
in response to calls to the Default: function,
as you can see from the following SConstruct file:
prog1 = Program('prog1.c') Default(prog1) print "DEFAULT_TARGETS is now", map(str, DEFAULT_TARGETS) prog2 = Program('prog2.c') Default(prog2) print "DEFAULT_TARGETS is now", map(str, DEFAULT_TARGETS) |
Which yields the output:
% scons scons: Reading SConscript files ... DEFAULT_TARGETS is now ['prog1'] DEFAULT_TARGETS is now ['prog1', 'prog2'] scons: done reading SConscript files. scons: Building targets ... cc -o prog1.o -c prog1.c cc -o prog1 prog1.o cc -o prog2.o -c prog2.c cc -o prog2 prog2.o scons: done building targets. |
In practice, this simply means that you
need to pay attention to the order in
which you call the Default function
and refer to the DEFAULT_TARGETS
list,
to make sure that you don't examine the
list before you've added the default targets
you expect to find in it.
BUILD_TARGETS
Variable
We've already been introduced to the
COMMAND_LINE_TARGETS
variable,
which contains a list of targets specified on the command line,
and the DEFAULT_TARGETS
variable,
which contains a list of targets specified
via calls to the Default method or function.
Sometimes, however,
you want a list of whatever targets
SCons will try to build,
regardless of whether the targets came from the
command line or a Default call.
You could code this up by hand, as follows:
if COMMAND_LINE_TARGETS: targets = COMMAND_LINE_TARGETS else: targets = DEFAULT_TARGETS |
SCons, however, provides a convenient
BUILD_TARGETS
variable
that eliminates the need for this by-hand manipulation.
Essentially, the BUILD_TARGETS
variable
contains a list of the command-line targets,
if any were specified,
and if no command-line targets were specified,
it contains a list of the targets specified
via the Default method or function.
Because BUILD_TARGETS
may contain a list of SCons nodes,
you must convert the list elements to strings
if you want to print them or look for a specific target name,
just like the DEFAULT_TARGETS
list:
prog1 = Program('prog1.c') Program('prog2.c') Default(prog1) print "BUILD_TARGETS is", map(str, BUILD_TARGETS) |
Notice how the value of BUILD_TARGETS
changes depending on whether a target is
specified on the command line:
% scons -Q BUILD_TARGETS is ['prog1'] cc -o prog1.o -c prog1.c cc -o prog1 prog1.o % scons -Q prog2 BUILD_TARGETS is ['prog2'] cc -o prog2.o -c prog2.c cc -o prog2 prog2.o % scons -Q -c . BUILD_TARGETS is ['.'] Removed prog1.o Removed prog1 Removed prog2.o Removed prog2 |
Once a program is built, it is often appropriate to install it in another directory for public use. You use the Install method to arrange for a program, or any other file, to be copied into a destination directory:
env = Environment() hello = env.Program('hello.c') env.Install('/usr/bin', hello) |
Note, however, that installing a file is still considered a type of file "build." This is important when you remember that the default behavior of SCons is to build files in or below the current directory. If, as in the example above, you are installing files in a directory outside of the top-level SConstruct file's directory tree, you must specify that directory (or a higher directory, such as /) for it to install anything there:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q /usr/bin Install file: "hello" as "/usr/bin/hello" |
It can, however, be cumbersome to remember (and type) the specific destination directory in which the program (or any other file) should be installed. This is an area where the Alias function comes in handy, allowing you, for example, to create a pseudo-target named install that can expand to the specified destination directory:
env = Environment() hello = env.Program('hello.c') env.Install('/usr/bin', hello) env.Alias('install', '/usr/bin') |
This then yields the more natural ability to install the program in its destination as follows:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q install Install file: "hello" as "/usr/bin/hello" |
You can install multiple files into a directory simply by calling the Install function multiple times:
env = Environment() hello = env.Program('hello.c') goodbye = env.Program('goodbye.c') env.Install('/usr/bin', hello) env.Install('/usr/bin', goodbye) env.Alias('install', '/usr/bin') |
Or, more succinctly, listing the multiple input files in a list (just like you can do with any other builder):
env = Environment() hello = env.Program('hello.c') goodbye = env.Program('goodbye.c') env.Install('/usr/bin', [hello, goodbye]) env.Alias('install', '/usr/bin') |
Either of these two examples yields:
% scons -Q install cc -o goodbye.o -c goodbye.c cc -o goodbye goodbye.o Install file: "goodbye" as "/usr/bin/goodbye" cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello" |
The Install method preserves the name of the file when it is copied into the destination directory. If you need to change the name of the file when you copy it, use the InstallAs function:
env = Environment() hello = env.Program('hello.c') env.InstallAs('/usr/bin/hello-new', hello) env.Alias('install', '/usr/bin') |
This installs the hello program with the name hello-new as follows:
% scons -Q install cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello-new" |
Lastly, if you have multiple files that all need to be installed with different file names, you can either call the InstallAs function multiple times, or as a shorthand, you can supply same-length lists for both the target and source arguments:
env = Environment() hello = env.Program('hello.c') goodbye = env.Program('goodbye.c') env.InstallAs(['/usr/bin/hello-new', '/usr/bin/goodbye-new'], [hello, goodbye]) env.Alias('install', '/usr/bin') |
In this case, the InstallAs function loops through both lists simultaneously, and copies each source file into its corresponding target file name:
% scons -Q install cc -o goodbye.o -c goodbye.c cc -o goodbye goodbye.o Install file: "goodbye" as "/usr/bin/goodbye-new" cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello-new" |
SCons provides a number of platform-independent functions,
called factories,
that perform common file system manipulations
like copying, moving or deleting files and directories,
or making directories.
These functions are factories
because they don't perform the action
at the time they're called,
they each return an Action
object
that can be executed at the appropriate time.
Suppose you want to arrange to make a copy of a file, and don't have a suitable pre-existing builder. [4] One way would be to use the Copy action factory in conjunction with the Command builder:
Command("file.out", "file.in", Copy("$TARGET", "$SOURCE")) |
Notice that the action returned by the Copy factory
will expand the $TARGET
and $SOURCE
strings
at the time file.out is built,
and that the order of the arguments
is the same as that of a builder itself--that is,
target first, followed by source:
% scons -Q Copy("file.out", "file.in") |
You can, of course, name a file explicitly
instead of using $TARGET
or $SOURCE
:
Command("file.out", [], Copy("$TARGET", "file.in")) |
Which executes as:
% scons -Q Copy("file.out", "file.in") |
The usefulness of the Copy factory becomes more apparent when you use it in a list of actions passed to the Command builder. For example, suppose you needed to run a file through a utility that only modifies files in-place, and can't "pipe" input to output. One solution is to copy the source file to a temporary file name, run the utility, and then copy the modified temporary file to the target, which the Copy factory makes extremely easy:
Command("file.out", "file.in", [ Copy("tempfile", "$SOURCE"), "modify tempfile", Copy("$TARGET", "tempfile"), ]) |
The output then looks like:
% scons -Q Copy("tempfile", "file.in") modify tempfile Copy("file.out", "tempfile") |
If you need to delete a file, then the Delete factory can be used in much the same way as the Copy factory. For example, if we want to make sure that the temporary file in our last example doesn't exist before we copy to it, we could add Delete to the beginning of the command list:
Command("file.out", "file.in", [ Delete("tempfile"), Copy("tempfile", "$SOURCE"), "modify tempfile", Copy("$TARGET", "tempfile"), ]) |
When then executes as follows:
% scons -Q Delete("tempfile") Copy("tempfile", "file.in") modify tempfile Copy("file.out", "tempfile") |
Of course, like all of these Action
factories,
the Delete factory also expands
$TARGET
and $SOURCE
variables appropriately.
For example:
Command("file.out", "file.in", [ Delete("$TARGET"), Copy("$TARGET", "$SOURCE") ]) |
Executes as:
% scons -Q Delete("file.out") Copy("file.out", "file.in") |
Note, however, that you typically don't need to call the Delete factory explicitly in this way; by default, SCons deletes its target(s) for you before executing any action.
One word of caution about using the Delete factory:
it has the same variable expansions available
as any other factory, including the $SOURCE
variable.
Specifying Delete("$SOURCE")
is not something you usually want to do!
The Move factory allows you to rename a file or directory. For example, if we don't want to copy the temporary file, we could use:
Command("file.out", "file.in", [ Copy("tempfile", "$SOURCE"), "modify tempfile", Move("$TARGET", "tempfile"), ]) |
Which would execute as:
% scons -Q Copy("tempfile", "file.in") modify tempfile Move("file.out", "tempfile") |
If you just need to update the recorded modification time for a file, use the Touch factory:
Command("file.out", "file.in", [ Copy("$TARGET", "$SOURCE"), Touch("$TARGET"), ]) |
Which executes as:
% scons -Q Copy("file.out", "file.in") Touch("file.out") |
If you need to create a directory, use the Mkdir factory. For example, if we need to process a file in a temporary directory in which the processing tool will create other files that we don't care about, you could use:
Command("file.out", "file.in", [ Delete("tempdir"), Mkdir("tempdir"), Copy("tempdir/${SOURCE.file}", "$SOURCE"), "process tempdir", Move("$TARGET", "tempdir/output_file"), Delete("tempdir"), ]) |
Which executes as:
% scons -Q Delete("tempdir") Mkdir("tempdir") Copy("tempdir/file.in", "file.in") process tempdir Move("file.out", "tempdir/output_file") scons: *** [file.out] No such file or directory |
To change permissions on a file or directory, use the Chmod factory. The permission argument uses POSIX-style permission bits and should typically be expressed as an octal, not decimal, number:
Command("file.out", "file.in", [ Copy("$TARGET", "$SOURCE"), Chmod("$TARGET", 0755), ]) |
Which executes:
% scons -Q Copy("file.out", "file.in") Chmod("file.out", 0755) |
We've been showing you how to use Action
factories
in the Command function.
You can also execute an Action
returned by a factory
(or actually, any Action
)
at the time the SConscript file is read
by using the Execute function.
For example, if we need to make sure that
a directory exists before we build any targets,
Execute(Mkdir('/tmp/my_temp_directory')) |
Notice that this will create the directory while the SConscript file is being read:
% scons scons: Reading SConscript files ... Mkdir("/tmp/my_temp_directory") scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets. |
If you're familiar with Python,
you may wonder why you would want to use this
instead of just calling the native Python
os.mkdir() function.
The advantage here is that the Mkdir
action will behave appropriately if the user
specifies the SCons -n
or
-q
options--that is,
it will print the action but not actually
make the directory when -n
is specified,
or make the directory but not print the action
when -q
is specified.
The Execute function returns the exit status or return value of the underlying action being executed. It will also print an error message if the action fails and returns a non-zero value. SCons will not, however, actually stop the build if the action fails. If you want the build to stop in response to a failure in an action called by Execute, you must do so by explicitly checking the return value and calling the Exit function (or a Python equivalent):
if Execute(Mkdir('/tmp/my_temp_directory')): # A problem occurred while making the temp directory. Exit(1) |
There are two occasions when SCons will, by default, remove target files. The first is when SCons determines that an target file needs to be rebuilt and removes the existing version of the target before executing The second is when SCons is invoked with the -c option to "clean" a tree of its built targets. These behaviours can be suppressed with the Precious and NoClean functions, respectively.
By default, SCons removes targets before building them. Sometimes, however, this is not what you want. For example, you may want to update a library incrementally, not by having it deleted and then rebuilt from all of the constituent object files. In such cases, you can use the Precious method to prevent SCons from removing the target before it is built:
env = Environment(RANLIBCOM='') lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c']) env.Precious(lib) |
Although the output doesn't look any different, SCons does not, in fact, delete the target library before rebuilding it:
% scons -Q cc -o f1.o -c f1.c cc -o f2.o -c f2.c cc -o f3.o -c f3.c ar rc libfoo.a f1.o f2.o f3.o |
SCons will, however, still delete files marked as Precious when the -c option is used.
By default, SCons removes all built targets when invoked with the -c option to clean a source tree of built targets. Sometimes, however, this is not what you want. For example, you may want to remove only intermediate generated files (such as object files), but leave the final targets (the libraries) untouched. In such cases, you can use the NoClean method to prevent SCons from removing a target during a clean:
env = Environment(RANLIBCOM='') lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c']) env.NoClean(lib) |
Notice that the libfoo.a is not listed as a removed file:
% scons -Q cc -o f1.o -c f1.c cc -o f2.o -c f2.c cc -o f3.o -c f3.c ar rc libfoo.a f1.o f2.o f3.o % scons -c scons: Reading SConscript files ... scons: done reading SConscript files. scons: Cleaning targets ... Removed f1.o Removed f2.o Removed f3.o scons: done cleaning targets. |
There may be additional files that you want removed when the -c option is used, but which SCons doesn't know about because they're not normal target files. For example, perhaps a command you invoke creates a log file as part of building the target file you want. You would like the log file cleaned, but you don't want to have to teach SCons that the command "builds" two files.
You can use the Clean function to arrange for additional files to be removed when the -c option is used. Notice, however, that the Clean function takes two arguments, and the second argument is the name of the additional file you want cleaned (foo.log in this example):
t = Command('foo.out', 'foo.in', 'build -o $TARGET $SOURCE') Clean(t, 'foo.log') |
The first argument is the target with which you want the cleaning of this additional file associated. In the above example, we've used the return value from the Command function, which represents the foo.out target. Now whenever the foo.out target is cleaned by the -c option, the foo.log file will be removed as well:
% scons -Q build -o foo.out foo.in % scons -Q -c Removed foo.out Removed foo.log |
The source code for large software projects rarely stays in a single directory, but is nearly always divided into a hierarchy of directories. Organizing a large software build using SCons involves creating a hierarchy of build scripts using the SConscript function.
As we've already seen, the build script at the top of the tree is called SConstruct. The top-level SConstruct file can use the SConscript function to include other subsidiary scripts in the build. These subsidiary scripts can, in turn, use the SConscript function to include still other scripts in the build. By convention, these subsidiary scripts are usually named SConscript. For example, a top-level SConstruct file might arrange for four subsidiary scripts to be included in the build as follows:
SConscript(['drivers/display/SConscript', 'drivers/mouse/SConscript', 'parser/SConscript', 'utilities/SConscript']) |
In this case, the SConstruct file lists all of the SConscript files in the build explicitly. (Note, however, that not every directory in the tree necessarily has an SConscript file.) Alternatively, the drivers subdirectory might contain an intermediate SConscript file, in which case the SConscript call in the top-level SConstruct file would look like:
SConscript(['drivers/SConscript', 'parser/SConscript', 'utilities/SConscript']) |
And the subsidiary SConscript file in the drivers subdirectory would look like:
SConscript(['display/SConscript', 'mouse/SConscript']) |
Whether you list all of the SConscript files in the top-level SConstruct file, or place a subsidiary SConscript file in intervening directories, or use some mix of the two schemes, is up to you and the needs of your software.
Subsidiary SConscript files make it easy to create a build hierarchy because all of the file and directory names in a subsidiary SConscript files are interpreted relative to the directory in which the SConscript file lives. Typically, this allows the SConscript file containing the instructions to build a target file to live in the same directory as the source files from which the target will be built, making it easy to update how the software is built whenever files are added or deleted (or other changes are made).
For example, suppose we want to build two programs prog1 and prog2 in two separate directories with the same names as the programs. One typical way to do this would be with a top-level SConstruct file like this:
SConscript(['prog1/SConscript', 'prog2/SConscript']) |
And subsidiary SConscript files that look like this:
env = Environment() env.Program('prog1', ['main.c', 'foo1.c', 'foo2.c']) |
And this:
env = Environment() env.Program('prog2', ['main.c', 'bar1.c', 'bar2.c']) |
Then, when we run SCons in the top-level directory, our build looks like:
% scons -Q cc -o prog1/foo1.o -c prog1/foo1.c cc -o prog1/foo2.o -c prog1/foo2.c cc -o prog1/main.o -c prog1/main.c cc -o prog1/prog1 prog1/main.o prog1/foo1.o prog1/foo2.o cc -o prog2/bar1.o -c prog2/bar1.c cc -o prog2/bar2.o -c prog2/bar2.c cc -o prog2/main.o -c prog2/main.c cc -o prog2/prog2 prog2/main.o prog2/bar1.o prog2/bar2.o |
Notice the following: First, you can have files with the same names in multiple directories, like main.c in the above example. Second, unlike standard recursive use of Make, SCons stays in the top-level directory (where the SConstruct file lives) and issues commands that use the path names from the top-level directory to the target and source files within the hierarchy.
If you need to use a file from another directory, it's sometimes more convenient to specify the path to a file in another directory from the top-level SConstruct directory, even when you're using that file in a subsidiary SConscript file in a subdirectory. You can tell SCons to interpret a path name as relative to the top-level SConstruct directory, not the local directory of the SConscript file, by appending a # (hash mark) to the beginning of the path name:
env = Environment() env.Program('prog', ['main.c', '#lib/foo1.c', 'foo2.c']) |
In this example, the lib directory is directly underneath the top-level SConstruct directory. If the above SConscript file is in a subdirectory named src/prog, the output would look like:
% scons -Q cc -o lib/foo1.o -c lib/foo1.c cc -o src/prog/foo2.o -c src/prog/foo2.c cc -o src/prog/main.o -c src/prog/main.c cc -o src/prog/prog src/prog/main.o lib/foo1.o src/prog/foo2.o |
(Notice that the lib/foo1.o object file is built in the same directory as its source file. See the Chapter called Separating Source and Build Directories, below, for information about how to build the object file in a different subdirectory.)
Of course, you can always specify an absolute path name for a file--for example:
env = Environment() env.Program('prog', ['main.c', '/usr/joe/lib/foo1.c', 'foo2.c']) |
Which, when executed, would yield:
% scons -Q cc -o src/prog/foo2.o -c src/prog/foo2.c cc -o src/prog/main.o -c src/prog/main.c cc -o /usr/joe/lib/foo1.o -c /usr/joe/lib/foo1.c cc -o src/prog/prog src/prog/main.o /usr/joe/lib/foo1.o src/prog/foo2.o |
(As was the case with top-relative path names, notice that the /usr/joe/lib/foo1.o object file is built in the same directory as its source file. See the Chapter called Separating Source and Build Directories, below, for information about how to build the object file in a different subdirectory.)
In the previous example, each of the subsidiary SConscript files created its own construction environment by calling Environment separately. This obviously works fine, but if each program must be built with the same construction variables, it's cumbersome and error-prone to initialize separate construction environments in the same way over and over in each subsidiary SConscript file.
SCons supports the ability to export variables from a parent SConscript file to its subsidiary SConscript files, which allows you to share common initialized values throughout your build hierarchy.
There are two ways to export a variable, such as a construction environment, from an SConscript file, so that it may be used by other SConscript files. First, you can call the Export function with a list of variables, or a string of white-space separated variable names. Each call to Export adds one or more variables to a global list of variables that are available for import by other SConscript files.
env = Environment() Export('env') |
You may export more than one variable name at a time:
env = Environment() debug = ARGUMENTS['debug'] Export('env', 'debug') |
Because white space is not legal in Python variable names, the Export function will even automatically split a string into separate names for you:
Export('env debug') |
Second, you can specify a list of variables to export as a second argument to the SConscript function call:
SConscript('src/SConscript', 'env') |
Or as the exports
keyword argument:
SConscript('src/SConscript', exports='env') |
These calls export the specified variables to only the listed SConscript files. You may, however, specify more than one SConscript file in a list:
SConscript(['src1/SConscript', 'src2/SConscript'], exports='env') |
This is functionally equivalent to
calling the SConscript function
multiple times with the same exports
argument,
one per SConscript file.
Once a variable has been exported from a calling SConscript file, it may be used in other SConscript files by calling the Import function:
Import('env') env.Program('prog', ['prog.c']) |
The Import call makes the env construction environment available to the SConscript file, after which the variable can be used to build programs, libraries, etc.
Like the Export function, the Import function can be used with multiple variable names:
Import('env', 'debug') env = env.Clone(DEBUG = debug) env.Program('prog', ['prog.c']) |
And the Import function will similarly split a string along white-space into separate variable names:
Import('env debug') env = env.Clone(DEBUG = debug) env.Program('prog', ['prog.c']) |
Lastly, as a special case, you may import all of the variables that have been exported by supplying an asterisk to the Import function:
Import('*') env = env.Clone(DEBUG = debug) env.Program('prog', ['prog.c']) |
If you're dealing with a lot of SConscript files, this can be a lot simpler than keeping arbitrary lists of imported variables in each file.
Sometimes, you would like to be able to use information from a subsidiary SConscript file in some way. For example, suppose that you want to create one library from source files scattered throughout a number of subsidiary SConscript files. You can do this by using the Return function to return values from the subsidiary SConscript files to the calling file.
If, for example, we have two subdirectories foo and bar that should each contribute a source file to a Library, what we'd like to be able to do is collect the object files from the subsidiary SConscript calls like this:
env = Environment() Export('env') objs = [] for subdir in ['foo', 'bar']: o = SConscript('%s/SConscript' % subdir) objs.append(o) env.Library('prog', objs) |
We can do this by using the Return function in the foo/SConscript file like this:
Import('env') obj = env.Object('foo.c') Return('obj') |
(The corresponding bar/SConscript file should be pretty obvious.) Then when we run SCons, the object files from the subsidiary subdirectories are all correctly archived in the desired library:
% scons -Q cc -o bar/bar.o -c bar/bar.c cc -o foo/foo.o -c foo/foo.c ar rc libprog.a foo/foo.o bar/bar.o ranlib libprog.a |
It's often useful to keep any built files completely separate from the source files. In SCons, this is usually done by creating one or more separate variant directory trees that are used to hold the built objects files, libraries, and executable programs, etc. for a specific flavor, or variant, of build. SCons provides two ways to do this, one through the SConscript function that we've already seen, and the second through a more flexible VariantDir function.
One historical note: the VariantDir function used to be called BuildDir. That name is still supported but has been deprecated because the SCons functionality differs from the model of a "build directory" implemented by other build systems like the GNU Autotools.
The most straightforward way to establish a variant directory tree
uses the fact that the usual way to
set up a build hierarchy is to have an
SConscript file in the source subdirectory.
If you then pass a variant_dir
argument to the
SConscript function call:
SConscript('src/SConscript', variant_dir='build') |
SCons will then build all of the files in the build subdirectory:
% ls src SConscript hello.c % scons -Q cc -o build/hello.o -c build/hello.c cc -o build/hello build/hello.o % ls build SConscript hello hello.c hello.o |
But wait a minute--what's going on here? SCons created the object file build/hello.o in the build subdirectory, as expected. But even though our hello.c file lives in the src subdirectory, SCons has actually compiled a build/hello.c file to create the object file.
What's happened is that SCons has duplicated the hello.c file from the src subdirectory to the build subdirectory, and built the program from there. The next section explains why SCons does this.
SCons duplicates source files in variant directory trees because it's the most straightforward way to guarantee a correct build regardless of include-file directory paths, relative references between files, or tool support for putting files in different locations, and the SCons philosophy is to, by default, guarantee a correct build in all cases.
The most direct reason to duplicate source files in variant directories is simply that some tools (mostly older vesions) are written to only build their output files in the same directory as the source files. In this case, the choices are either to build the output file in the source directory and move it to the variant directory, or to duplicate the source files in the variant directory.
Additionally, relative references between files can cause problems if we don't just duplicate the hierarchy of source files in the variant directory. You can see this at work in use of the C preprocessor #include mechanism with double quotes, not angle brackets:
#include "file.h" |
The de facto standard behavior for most C compilers in this case is to first look in the same directory as the source file that contains the #include line, then to look in the directories in the preprocessor search path. Add to this that the SCons implementation of support for code repositories (described below) means not all of the files will be found in the same directory hierarchy, and the simplest way to make sure that the right include file is found is to duplicate the source files into the variant directory, which provides a correct build regardless of the original location(s) of the source files.
Although source-file duplication guarantees a correct build even in these end-cases, it can usually be safely disabled. The next section describes how you can disable the duplication of source files in the variant directory.
In most cases and with most tool sets, SCons can place its target files in a build subdirectory without duplicating the source files and everything will work just fine. You can disable the default SCons behavior by specifying duplicate=0 when you call the SConscript function:
SConscript('src/SConscript', variant_dir='build', duplicate=0) |
When this flag is specified, SCons uses the variant directory like most people expect--that is, the output files are placed in the variant directory while the source files stay in the source directory:
% ls src SConscript hello.c % scons -Q cc -c src/hello.c -o build/hello.o cc -o build/hello build/hello.o % ls build hello hello.o |
Use the VariantDir function to establish that target files should be built in a separate directory from the source files:
VariantDir('build', 'src') env = Environment() env.Program('build/hello.c') |
Note that when you're not using an SConscript file in the src subdirectory, you must actually specify that the program must be built from the build/hello.c file that SCons will duplicate in the build subdirectory.
When using the VariantDir function directly, SCons still duplicates the source files in the variant directory by default:
% ls src hello.c % scons -Q cc -o build/hello.o -c build/hello.c cc -o build/hello build/hello.o % ls build hello hello.c hello.o |
You can specify the same duplicate=0 argument that you can specify for an SConscript call:
VariantDir('build', 'src', duplicate=0) env = Environment() env.Program('build/hello.c') |
In which case SCons will disable duplication of the source files:
% ls src hello.c % scons -Q cc -o build/hello.o -c src/hello.c cc -o build/hello build/hello.o % ls build hello hello.o |
Even when using the VariantDir function, it's much more natural to use it with a subsidiary SConscript file. For example, if the src/SConscript looks like this:
env = Environment() env.Program('hello.c') |
Then our SConstruct file could look like:
VariantDir('build', 'src') SConscript('build/SConscript') |
Yielding the following output:
% ls src SConscript hello.c % scons -Q cc -o build/hello.o -c build/hello.c cc -o build/hello build/hello.o % ls build SConscript hello hello.c hello.o |
Notice that this is completely equivalent to the use of SConscript that we learned about in the previous section.
The Glob file name pattern matching function works just as usual when using VariantDir. For example, if the src/SConscript looks like this:
env = Environment() env.Program('hello', Glob('*.c')) |
Then with the same SConstruct file as in the previous section, and source files f1.c and f2.c in src, we would see the following output:
% ls src SConscript f1.c f2.c f2.h % scons -Q cc -o build/f1.o -c build/f1.c cc -o build/f2.o -c build/f2.c cc -o build/hello build/f1.o build/f2.o % ls build SConscript f1.c f1.o f2.c f2.h f2.o hello |
The Glob function returns Nodes in the build/ tree, as you'd expect.
The variant_dir
keyword argument of
the SConscript function provides everything
we need to show how easy it is to create
variant builds using SCons.
Suppose, for example, that we want to
build a program for both Windows and Linux platforms,
but that we want to build it in a shared directory
with separate side-by-side build directories
for the Windows and Linux versions of the program.
platform = ARGUMENTS.get('OS', Platform()) include = "#export/$PLATFORM/include" lib = "#export/$PLATFORM/lib" bin = "#export/$PLATFORM/bin" env = Environment(PLATFORM = platform, BINDIR = bin, INCDIR = include, LIBDIR = lib, CPPPATH = [include], LIBPATH = [lib], LIBS = 'world') Export('env') env.SConscript('src/SConscript', variant_dir='build/$PLATFORM') |
This SConstruct file, when run on a Linux system, yields:
% scons -Q OS=linux Install file: "build/linux/world/world.h" as "export/linux/include/world.h" cc -o build/linux/hello/hello.o -c -Iexport/linux/include build/linux/hello/hello.c cc -o build/linux/world/world.o -c -Iexport/linux/include build/linux/world/world.c ar rc build/linux/world/libworld.a build/linux/world/world.o ranlib build/linux/world/libworld.a Install file: "build/linux/world/libworld.a" as "export/linux/lib/libworld.a" cc -o build/linux/hello/hello build/linux/hello/hello.o -Lexport/linux/lib -lworld Install file: "build/linux/hello/hello" as "export/linux/bin/hello" |
The same SConstruct file on Windows would build:
C:\>scons -Q OS=windows Install file: "build/windows/world/world.h" as "export/windows/include/world.h" cl /Fobuild\windows\hello\hello.obj /c build\windows\hello\hello.c /nologo /Iexport\windows\include cl /Fobuild\windows\world\world.obj /c build\windows\world\world.c /nologo /Iexport\windows\include lib /nologo /OUT:build\windows\world\world.lib build\windows\world\world.obj Install file: "build/windows/world/world.lib" as "export/windows/lib/world.lib" link /nologo /OUT:build\windows\hello\hello.exe /LIBPATH:export\windows\lib world.lib build\windows\hello\hello.obj Install file: "build/windows/hello/hello.exe" as "export/windows/bin/hello.exe" |
Although SCons provides many useful methods
for building common software products:
programs, libraries, documents.
you frequently want to be
able to build some other type of file
not supported directly by SCons
Fortunately, SCons makes it very easy
to define your own Builder
objects
for any custom file types you want to build.
(In fact, the SCons interfaces for creating
Builder
objects are flexible enough and easy enough to use
that all of the the SCons built-in Builder
objects
are created the mechanisms described in this section.)
The simplest Builder
to create is
one that executes an external command.
For example, if we want to build
an output file by running the contents
of the input file through a command named
foobuild,
creating that Builder
might look like:
bld = Builder(action = 'foobuild < $SOURCE > $TARGET') |
All the above line does is create a free-standing
Builder
object.
The next section will show us how to actually use it.
A Builder
object isn't useful
until it's attached to a construction environment
so that we can call it to arrange
for files to be built.
This is done through the $BUILDERS
construction variable in an environment.
The $BUILDERS
variable is a Python dictionary
that maps the names by which you want to call
various Builder
objects to the objects themselves.
For example, if we want to call the
Builder
we just defined by the name
Foo,
our SConstruct file might look like:
bld = Builder(action = 'foobuild < $SOURCE > $TARGET') env = Environment(BUILDERS = {'Foo' : bld}) |
With the Builder
so attached to our construction environment
we can now actually call it like so:
env.Foo('file.foo', 'file.input') |
Then when we run SCons it looks like:
% scons -Q foobuild < file.input > file.foo |
Note, however, that the default $BUILDERS
variable in a construction environment
comes with a default set of Builder
objects
already defined:
Program, Library, etc.
And when we explicitly set the $BUILDERS
variable
when we create the construction environment,
the default Builder
s are no longer part of
the environment:
bld = Builder(action = 'foobuild < $SOURCE > $TARGET') env = Environment(BUILDERS = {'Foo' : bld}) env.Foo('file.foo', 'file.input') env.Program('hello.c') |
% scons -Q AttributeError: SConsEnvironment instance has no attribute 'Program': File "/home/my/project/SConstruct", line 4: env.Program('hello.c') |
To be able to use both our own defined Builder
objects
and the default Builder
objects in the same construction environment,
you can either add to the $BUILDERS
variable
using the Append function:
env = Environment() bld = Builder(action = 'foobuild < $SOURCE > $TARGET') env.Append(BUILDERS = {'Foo' : bld}) env.Foo('file.foo', 'file.input') env.Program('hello.c') |
Or you can explicitly set the appropriately-named
key in the $BUILDERS
dictionary:
env = Environment() bld = Builder(action = 'foobuild < $SOURCE > $TARGET') env['BUILDERS']['Foo'] = bld env.Foo('file.foo', 'file.input') env.Program('hello.c') |
Either way, the same construction environment
can then use both the newly-defined
Foo Builder
and the default Program Builder
:
% scons -Q foobuild < file.input > file.foo cc -o hello.o -c hello.c cc -o hello hello.o |
By supplying additional information
when you create a Builder
,
you can let SCons add appropriate file
suffixes to the target and/or the source file.
For example, rather than having to specify
explicitly that you want the Foo
Builder
to build the file.foo
target file from the file.input source file,
you can give the .foo
and .input suffixes to the Builder
,
making for more compact and readable calls to
the Foo Builder
:
bld = Builder(action = 'foobuild < $SOURCE > $TARGET', suffix = '.foo', src_suffix = '.input') env = Environment(BUILDERS = {'Foo' : bld}) env.Foo('file1') env.Foo('file2') |
% scons -Q foobuild < file1.input > file1.foo foobuild < file2.input > file2.foo |
You can also supply a prefix keyword argument if it's appropriate to have SCons append a prefix to the beginning of target file names.
In SCons, you don't have to call an external command
to build a file.
You can, instead, define a Python function
that a Builder
object can invoke
to build your target file (or files).
Such a builder function definition looks like:
def build_function(target, source, env): # Code to build "target" from "source" return None |
The arguments of a builder function are:
A list of Node objects representing the target or targets to be built by this builder function. The file names of these target(s) may be extracted using the Python str function.
A list of Node objects representing the sources to be used by this builder function to build the targets. The file names of these source(s) may be extracted using the Python str function.
The construction environment used for building the target(s). The builder function may use any of the environment's construction variables in any way to affect how it builds the targets.
The builder function must return a 0 or None value if the target(s) are built successfully. The builder function may raise an exception or return any non-zero value to indicate that the build is unsuccessful,
Once you've defined the Python function
that will build your target file,
defining a Builder
object for it is as
simple as specifying the name of the function,
instead of an external command,
as the Builder
's
action
argument:
def build_function(target, source, env): # Code to build "target" from "source" return None bld = Builder(action = build_function, suffix = '.foo', src_suffix = '.input') env = Environment(BUILDERS = {'Foo' : bld}) env.Foo('file') |
And notice that the output changes slightly, reflecting the fact that a Python function, not an external command, is now called to build the target file:
% scons -Q build_function(["file.foo"], ["file.input"]) |
SCons Builder objects can create an action "on the fly" by using a function called a generator. This provides a great deal of flexibility to construct just the right list of commands to build your target. A generator looks like:
def generate_actions(source, target, env, for_signature): return 'foobuild < %s > %s' % (target[0], source[0]) |
The arguments of a generator are:
A list of Node objects representing the sources to be built by the command or other action generated by this function. The file names of these source(s) may be extracted using the Python str function.
A list of Node objects representing the target or targets to be built by the command or other action generated by this function. The file names of these target(s) may be extracted using the Python str function.
The construction environment used for building the target(s). The generator may use any of the environment's construction variables in any way to determine what command or other action to return.
A flag that specifies whether the generator is being called to contribute to a build signature, as opposed to actually executing the command.
The generator must return a command string or other action that will be used to build the specified target(s) from the specified source(s).
Once you've defined a generator,
you create a Builder
to use it
by specifying the generator keyword argument
instead of action.
def generate_actions(source, target, env, for_signature): return 'foobuild < %s > %s' % (source[0], target[0]) bld = Builder(generator = generate_actions, suffix = '.foo', src_suffix = '.input') env = Environment(BUILDERS = {'Foo' : bld}) env.Foo('file') |
% scons -Q foobuild < file.input > file.foo |
Note that it's illegal to specify both an
action
and a
generator
for a Builder
.
SCons supports the ability for a Builder to modify the lists of target(s) from the specified source(s). You do this by defining an emitter function that takes as its arguments the list of the targets passed to the builder, the list of the sources passed to the builder, and the construction environment. The emitter function should return the modified lists of targets that should be built and sources from which the targets will be built.
For example, suppose you want to define a Builder that always calls a foobuild program, and you want to automatically add a new target file named new_target and a new source file named new_source whenever it's called. The SConstruct file might look like this:
def modify_targets(target, source, env): target.append('new_target') source.append('new_source') return target, source bld = Builder(action = 'foobuild $TARGETS - $SOURCES', suffix = '.foo', src_suffix = '.input', emitter = modify_targets) env = Environment(BUILDERS = {'Foo' : bld}) env.Foo('file') |
And would yield the following output:
% scons -Q foobuild file.foo new_target - file.input new_source |
One very flexible thing that you can is specify
use a construction variable to specify
different emitter functions for different
construction variable.
To do this, specify a string
containing a construction variable
expansion as the emitter when you call
the Builder
function,
and set that construction variable to
the desired emitter function
in different construction environments:
bld = Builder(action = 'my_command $SOURCES > $TARGET', suffix = '.foo', src_suffix = '.input', emitter = '$MY_EMITTER') def modify1(target, source, env): return target, source + ['modify1.in'] def modify2(target, source, env): return target, source + ['modify2.in'] env1 = Environment(BUILDERS = {'Foo' : bld}, MY_EMITTER = modify1) env2 = Environment(BUILDERS = {'Foo' : bld}, MY_EMITTER = modify2) env1.Foo('file1') env2.Foo('file2') import os env1['ENV']['PATH'] = env2['ENV']['PATH'] + os.pathsep + os.getcwd() env2['ENV']['PATH'] = env2['ENV']['PATH'] + os.pathsep + os.getcwd() |
bld = Builder(action = 'my_command $SOURCES > $TARGET', suffix = '.foo', src_suffix = '.input', emitter = '$MY_EMITTER') def modify1(target, source, env): return target, source + ['modify1.in'] def modify2(target, source, env): return target, source + ['modify2.in'] env1 = Environment(BUILDERS = {'Foo' : bld}, MY_EMITTER = modify1) env2 = Environment(BUILDERS = {'Foo' : bld}, MY_EMITTER = modify2) env1.Foo('file1') env2.Foo('file2') |
In this example, the modify1.in and modify2.in files get added to the source lists of the different commands:
% scons -Q my_command file1.input modify1.in > file1.foo my_command file2.input modify2.in > file2.foo |
The site_scons directory gives you a place to put Python modules you can import into your SConscripts (site_scons), add-on tools that can integrate into SCons (site_scons/site_tools), and a site_scons/site_init.py file that gets read before any SConstruct or SConscript, allowing you to change SCons's default behavior.
If you get a tool from somewhere (the SCons wiki or a third party, for instance) and you'd like to use it in your project, the site_scons dir is the simplest place to put it. Tools come in two flavors; either a Python function that operates on an Environment or a Python file containing two functions, exists() and generate().
A single-function Tool can just be included in your site_scons/site_init.py file where it will be parsed and made available for use. For instance, you could have a site_scons/site_init.py file like this:
def TOOL_ADD_HEADER(env): """A Tool to add a header from $HEADER to the source file""" add_header = Builder(action=['echo "$HEADER" > $TARGET', 'cat $SOURCE >> $TARGET']) env.Append(BUILDERS = {'AddHeader' : add_header}) env['HEADER'] = '' # set default value |
and a SConstruct like this:
# Use TOOL_ADD_HEADER from site_scons/site_init.py env=Environment(tools=['default', TOOL_ADD_HEADER], HEADER="=====") env.AddHeader('tgt', 'src') |
The TOOL_ADD_HEADER tool method will be called to add the AddHeader tool to the environment.
Similarly, a more full-fledged tool with exists() and generate() methods can be installed in site_scons/site_tools/toolname.py. Since site_scons/site_tools is automatically added to the head of the tool search path, any tool found there will be available to all environments. Furthermore, a tool found there will override a built-in tool of the same name, so if you need to change the behavior of a built-in tool, site_scons gives you the hook you need.
Many people have a library of utility Python functions they'd like to include in SConscripts; just put that module in site_scons/my_utils.py or any valid Python module name of your choice. For instance you can do something like this in site_scons/my_utils.py to add a build_id method:
def build_id(): """Return a build ID (stub version)""" return "100" |
And then in your SConscript or any sub-SConscript anywhere in your build, you can import my_utils and use it:
import my_utils print "build_id=" + my_utils.build_id() |
If you have a machine-wide site dir you'd like to use instead of ./site_scons, use the --site-dir option to point to your dir. site_init.py and site_tools will be located under that dir. To avoid using a site_scons dir at all, even if it exists, use the --no-site-dir option.
Creating a Builder
and attaching it to a construction environment
allows for a lot of flexibility when you
want to re-use actions
to build multiple files of the same type.
This can, however, be cumbersome
if you only need to execute one specific command
to build a single file (or group of files).
For these situations, SCons supports a
Command Builder
that arranges
for a specific action to be executed
to build a specific file or files.
This looks a lot like the other builders
(like Program, Object, etc.),
but takes as an additional argument
the command to be executed to build the file:
env = Environment() env.Command('foo.out', 'foo.in', "sed 's/x/y/' < $SOURCE > $TARGET") |
When executed,
SCons runs the specified command,
substituting $SOURCE
and $TARGET
as expected:
% scons -Q sed 's/x/y/' < foo.in > foo.out |
This is often more convenient than
creating a Builder
object
and adding it to the $BUILDERS
variable
of a construction environment
Note that the action you specify to the
Command Builder
can be any legal SCons Action
,
such as a Python function:
env = Environment() def build(target, source, env): # Whatever it takes to build return None env.Command('foo.out', 'foo.in', build) |
Which executes as follows:
% scons -Q build(["foo.out"], ["foo.in"]) |
Note that $SOURCE
and $TARGET
are expanded
in the source and target as well as of SCons 1.1,
so you can write:
env.Command('${SOURCE.basename}.out', 'foo.in', build) |
which does the same thing as the previous example, but allows you to avoid repeating yourself.
The AddMethod function is used to add a method
to an environment. It's typically used to add a "pseudo-builder,"
a function that looks like a Builder
but
wraps up calls to multiple other Builder
s
or otherwise processes its arguments
before calling one or more Builder
s.
In the following example,
we want to install the program into the standard
/usr/bin directory hierarchy,
but also copy it into a local install/bin
directory from which a package might be built:
def install_in_bin_dirs(env, source): """Install source in both bin dirs""" i1 = env.Install("$BIN", source) i2 = env.Install("$LOCALBIN", source) return [i1[0], i2[0]] # Return a list, like a normal builder env = Environment(BIN='/usr/bin', LOCALBIN='#install/bin') env.AddMethod(install_in_bin_dirs, "InstallInBinDirs") env.InstallInBinDirs(Program('hello.c')) # installs hello in both bin dirs |
This produces the following:
% scons -Q / cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello" Install file: "hello" as "install/bin/hello" |
As mentioned, a psuedo-builder also provides more flexibility
in parsing arguments than you can get with a Builder
.
The next example shows a pseudo-builder with a
named argument that modifies the filename, and a separate argument
for the resource file (rather than having the builder figure it out
by file extension). This example also demonstrates using the global
AddMethod function to add a method to the global Environment class,
so it will be used in all subsequently created environments.
def BuildTestProg(env, testfile, resourcefile, testdir="tests"): """Build the test program; prepends "test_" to src and target, and puts target into testdir.""" srcfile = "test_%s.c" % testfile target = "%s/test_%s" % (testdir, testfile) if env['PLATFORM'] == 'win32': resfile = env.RES(resourcefile) p = env.Program(target, [srcfile, resfile]) else: p = env.Program(target, srcfile) return p AddMethod(Environment, BuildTestProg) env = Environment() env.BuildTestProg('stuff', resourcefile='res.rc') |
This produces the following on Linux:
% scons -Q cc -o test_stuff.o -c test_stuff.c cc -o tests/test_stuff test_stuff.o |
And the following on Windows:
C:\>scons -Q rc /fores.res res.rc cl /Fotest_stuff.obj /c test_stuff.c /nologo link /nologo /OUT:tests\test_stuff.exe test_stuff.obj res.res |
Using AddMethod is better than just adding an instance method to a construction environment because it gets called as a proper method, and because AddMethod provides for copying the method to any clones of the construction environment instance.
SCons has built-in scanners that know how to look in C, Fortran and IDL source files for information about other files that targets built from those files depend on--for example, in the case of files that use the C preprocessor, the .h files that are specified using #include lines in the source. You can use the same mechanisms that SCons uses to create its built-in scanners to write scanners of your own for file types that SCons does not know how to scan "out of the box."
Suppose, for example, that we want to create a simple scanner for .foo files. A .foo file contains some text that will be processed, and can include other files on lines that begin with include followed by a file name:
include filename.foo |
Scanning a file will be handled by a Python function that you must supply. Here is a function that will use the Python re module to scan for the include lines in our example:
import re include_re = re.compile(r'^include\s+(\S+)$', re.M) def kfile_scan(node, env, path, arg): contents = node.get_contents() return include_re.findall(contents) |
The scanner function must accept the four specified arguments and return a list of implicit dependencies. Presumably, these would be dependencies found from examining the contents of the file, although the function can perform any manipulation at all to generate the list of dependencies.
An SCons node object representing the file being scanned. The path name to the file can be used by converting the node to a string using the str() function, or an internal SCons get_contents() object method can be used to fetch the contents.
The construction environment in effect for this scan. The scanner function may choose to use construction variables from this environment to affect its behavior.
A list of directories that form the search path for included files
for this scanner.
This is how SCons handles the $CPPPATH
and $LIBPATH
variables.
An optional argument that you can choose to have passed to this scanner function by various scanner instances.
A Scanner object is created using the Scanner
function,
which typically takes an skeys argument
to associate the type of file suffix with this scanner.
The Scanner object must then be associated with the
$SCANNERS
construction variable of a construction environment,
typically by using the Append method:
kscan = Scanner(function = kfile_scan, skeys = ['.k']) env.Append(SCANNERS = kscan) |
When we put it all together, it looks like:
import re include_re = re.compile(r'^include\s+(\S+)$', re.M) def kfile_scan(node, env, path): contents = node.get_contents() includes = include_re.findall(contents) return includes kscan = Scanner(function = kfile_scan, skeys = ['.k']) env = Environment(ENV = {'PATH' : '/usr/local/bin'}) env.Append(SCANNERS = kscan) env.Command('foo', 'foo.k', 'kprocess < $SOURCES > $TARGET') |
Often, a software project will have one or more central repositories, directory trees that contain source code, or derived files, or both. You can eliminate additional unnecessary rebuilds of files by having SCons use files from one or more code repositories to build files in your local build tree.
It's often useful to allow multiple programmers working on a project to build software from source files and/or derived files that are stored in a centrally-accessible repository, a directory copy of the source code tree. (Note that this is not the sort of repository maintained by a source code management system like BitKeeper, CVS, or Subversion.) You use the Repository method to tell SCons to search one or more central code repositories (in order) for any source files and derived files that are not present in the local build tree:
env = Environment() env.Program('hello.c') Repository('/usr/repository1', '/usr/repository2') |
Multiple calls to the Repository method will simply add repositories to the global list that SCons maintains, with the exception that SCons will automatically eliminate the current directory and any non-existent directories from the list.
The above example specifies that SCons will first search for files under the /usr/repository1 tree and next under the /usr/repository2 tree. SCons expects that any files it searches for will be found in the same position relative to the top-level directory. In the above example, if the hello.c file is not found in the local build tree, SCons will search first for a /usr/repository1/hello.c file and then for a /usr/repository2/hello.c file to use in its place.
So given the SConstruct file above, if the hello.c file exists in the local build directory, SCons will rebuild the hello program as normal:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o |
If, however, there is no local hello.c file, but one exists in /usr/repository1, SCons will recompile the hello program from the source file it finds in the repository:
% scons -Q cc -o hello.o -c /usr/repository1/hello.c cc -o hello hello.o |
And similarly, if there is no local hello.c file and no /usr/repository1/hello.c, but one exists in /usr/repository2:
% scons -Q cc -o hello.o -c /usr/repository2/hello.c cc -o hello hello.o |
We've already seen that SCons will scan the contents of
a source file for #include file names
and realize that targets built from that source file
also depend on the #include file(s).
For each directory in the $CPPPATH
list,
SCons will actually search the corresponding directories
in any repository trees and establish the
correct dependencies on any
#include files that it finds
in repository directory.
Unless the C compiler also knows about these directories in the repository trees, though, it will be unable to find the #include files. If, for example, the hello.c file in our previous example includes the hello.h; in its current directory, and the hello.h; only exists in the repository:
% scons -Q cc -o hello.o -c hello.c hello.c:1: hello.h: No such file or directory |
In order to inform the C compiler about the repositories,
SCons will add appropriate
-I flags to the compilation commands
for each directory in the $CPPPATH
list.
So if we add the current directory to the
construction environment $CPPPATH
like so:
env = Environment(CPPPATH = ['.']) env.Program('hello.c') Repository('/usr/repository1') |
Then re-executing SCons yields:
% scons -Q cc -o hello.o -c -I. -I/usr/repository1 hello.c cc -o hello hello.o |
The order of the -I options replicates,
for the C preprocessor,
the same repository-directory search path
that SCons uses for its own dependency analysis.
If there are multiple repositories and multiple $CPPPATH
directories, SCons will add the repository directories
to the beginning of each $CPPPATH
directory,
rapidly multiplying the number of -I flags.
If, for example, the $CPPPATH
contains three directories
(and shorter repository path names!):
env = Environment(CPPPATH = ['dir1', 'dir2', 'dir3']) env.Program('hello.c') Repository('/r1', '/r2') |
Then we'll end up with nine -I options
on the command line,
three (for each of the $CPPPATH
directories)
times three (for the local directory plus the two repositories):
% scons -Q cc -o hello.o -c -Idir1 -I/r1/dir1 -I/r2/dir1 -Idir2 -I/r1/dir2 -I/r2/dir2 -Idir3 -I/r1/dir3 -I/r2/dir3 hello.c cc -o hello hello.o |
SCons relies on the C compiler's -I options to control the order in which the preprocessor will search the repository directories for #include files. This causes a problem, however, with how the C preprocessor handles #include lines with the file name included in double-quotes.
As we've seen, SCons will compile the hello.c file from the repository if it doesn't exist in the local directory. If, however, the hello.c file in the repository contains a #include line with the file name in double quotes:
#include "hello.h" int main(int argc, char *argv[]) { printf(HELLO_MESSAGE); return (0); } |
Then the C preprocessor will always use a hello.h file from the repository directory first, even if there is a hello.h file in the local directory, despite the fact that the command line specifies -I as the first option:
% scons -Q cc -o hello.o -c -I. -I/usr/repository1 /usr/repository1/hello.c cc -o hello hello.o |
This behavior of the C preprocessor--always search for a #include file in double-quotes first in the same directory as the source file, and only then search the -I--can not, in general, be changed. In other words, it's a limitation that must be lived with if you want to use code repositories in this way. There are three ways you can possibly work around this C preprocessor behavior:
Some modern versions of C compilers do have an option
to disable or control this behavior.
If so, add that option to $CFLAGS
(or $CXXFLAGS
or both) in your construction environment(s).
Make sure the option is used for all construction
environments that use C preprocessing!
Change all occurrences of #include "file.h" to #include <file.h>. Use of #include with angle brackets does not have the same behavior--the -I directories are searched first for #include files--which gives SCons direct control over the list of directories the C preprocessor will search.
Require that everyone working with compilation from repositories check out and work on entire directories of files, not individual files. (If you use local wrapper scripts around your source code control system's command, you could add logic to enforce this restriction there.
SCons will also search in repositories for the SConstruct file and any specified SConscript files. This poses a problem, though: how can SCons search a repository tree for an SConstruct file if the SConstruct file itself contains the information about the pathname of the repository? To solve this problem, SCons allows you to specify repository directories on the command line using the -Y option:
% scons -Q -Y /usr/repository1 -Y /usr/repository2 |
When looking for source or derived files, SCons will first search the repositories specified on the command line, and then search the repositories specified in the SConstruct or SConscript files.
If a repository contains not only source files, but also derived files (such as object files, libraries, or executables), SCons will perform its normal MD5 signature calculation to decide if a derived file in a repository is up-to-date, or the derived file must be rebuilt in the local build directory. For the SCons signature calculation to work correctly, a repository tree must contain the .sconsign files that SCons uses to keep track of signature information.
Usually, this would be done by a build integrator who would run SCons in the repository to create all of its derived files and .sconsign files, or who would run SCons in a separate build directory and copy the resulting tree to the desired repository:
% cd /usr/repository1 % scons -Q cc -o file1.o -c file1.c cc -o file2.o -c file2.c cc -o hello.o -c hello.c cc -o hello hello.o file1.o file2.o |
(Note that this is safe even if the SConstruct file lists /usr/repository1 as a repository, because SCons will remove the current build directory from its repository list for that invocation.)
Now, with the repository populated, we only need to create the one local source file we're interested in working with at the moment, and use the -Y option to tell SCons to fetch any other files it needs from the repository:
% cd $HOME/build % edit hello.c % scons -Q -Y /usr/repository1 cc -c -o hello.o hello.c cc -o hello hello.o /usr/repository1/file1.o /usr/repository1/file2.o |
Notice that SCons realizes that it does not need to rebuild local copies file1.o and file2.o files, but instead uses the already-compiled files from the repository.
If the repository tree contains the complete results of a build, and we try to build from the repository without any files in our local tree, something moderately surprising happens:
% mkdir $HOME/build2 % cd $HOME/build2 % scons -Q -Y /usr/all/repository hello scons: `hello' is up-to-date. |
Why does SCons say that the hello program is up-to-date when there is no hello program in the local build directory? Because the repository (not the local directory) contains the up-to-date hello program, and SCons correctly determines that nothing needs to be done to rebuild that up-to-date copy of the file.
There are, however, many times when you want to ensure that a local copy of a file always exists. A packaging or testing script, for example, may assume that certain generated files exist locally. To tell SCons to make a copy of any up-to-date repository file in the local build directory, use the Local function:
env = Environment() hello = env.Program('hello.c') Local(hello) |
If we then run the same command, SCons will make a local copy of the program from the repository copy, and tell you that it is doing so:
% scons -Y /usr/all/repository hello Local copy of hello from /usr/all/repository/hello scons: `hello' is up-to-date. |
(Notice that, because the act of making the local copy is not considered a "build" of the hello file, SCons still reports that it is up-to-date.)
SCons has integrated support for multi-platform build configuration similar to that offered by GNU Autoconf, such as figuring out what libraries or header files are available on the local system. This section describes how to use this SCons feature.
![]() | This chapter is still under development, so not everything is explained as well as it should be. See the SCons man page for additional information. |
The basic framework for multi-platform build configuration in SCons is to attach a configure context to a construction environment by calling the Configure function, perform a number of checks for libraries, functions, header files, etc., and to then call the configure context's Finish method to finish off the configuration:
env = Environment() conf = Configure(env) # Checks for libraries, header files, etc. go here! env = conf.Finish() |
SCons provides a number of basic checks, as well as a mechanism for adding your own custom checks.
Note that SCons uses its own dependency mechanism to determine when a check needs to be run--that is, SCons does not run the checks every time it is invoked, but caches the values returned by previous checks and uses the cached values unless something has changed. This saves a tremendous amount of developer time while working on cross-platform build issues.
The next sections describe the basic checks that SCons supports, as well as how to add your own custom checks.
Testing the existence of a header file requires knowing what language the header file is. A configure context has a CheckCHeader method that checks for the existence of a C header file:
env = Environment() conf = Configure(env) if not conf.CheckCHeader('math.h'): print 'Math.h must be installed!' Exit(1) if conf.CheckCHeader('foo.h'): conf.env.Append('-DHAS_FOO_H') env = conf.Finish() |
Note that you can choose to terminate the build if a given header file doesn't exist, or you can modify the construction environment based on the existence of a header file.
If you need to check for the existence a C++ header file, use the CheckCXXHeader method:
env = Environment() conf = Configure(env) if not conf.CheckCXXHeader('vector.h'): print 'vector.h must be installed!' Exit(1) env = conf.Finish() |
Check for the availability of a specific function using the CheckFunc method:
env = Environment() conf = Configure(env) if not conf.CheckFunc('strcpy'): print 'Did not find strcpy(), using local version' conf.env.Append(CPPDEFINES = '-Dstrcpy=my_local_strcpy') env = conf.Finish() |
Check for the availability of a library using the CheckLib method. You only specify the basename of the library, you don't need to add a lib prefix or a .a or .lib suffix:
env = Environment() conf = Configure(env) if not conf.CheckLib('m'): print 'Did not find libm.a or m.lib, exiting!' Exit(1) env = conf.Finish() |
Because the ability to use a library successfully often depends on having access to a header file that describes the library's interface, you can check for a library and a header file at the same time by using the CheckLibWithHeader method:
env = Environment() conf = Configure(env) if not conf.CheckLibWithHeader('m', 'math.h', 'c'): print 'Did not find libm.a or m.lib, exiting!' Exit(1) env = conf.Finish() |
This is essentially shorthand for separate calls to the CheckHeader and CheckLib functions.
Check for the availability of a typedef by using the CheckType method:
env = Environment() conf = Configure(env) if not conf.CheckType('off_t'): print 'Did not find off_t typedef, assuming int' conf.env.Append(CCFLAGS = '-Doff_t=int') env = conf.Finish() |
You can also add a string that will be placed at the beginning of the test file that will be used to check for the typedef. This provide a way to specify files that must be included to find the typedef:
env = Environment() conf = Configure(env) if not conf.CheckType('off_t', '#include <sys/types.h>\n'): print 'Did not find off_t typedef, assuming int' conf.env.Append(CCFLAGS = '-Doff_t=int') env = conf.Finish() |
A custom check is a Python function that checks for a certain condition to exist on the running system, usually using methods that SCons supplies to take care of the details of checking whether a compilation succeeds, a link succeeds, a program is runnable, etc. A simple custom check for the existence of a specific library might look as follows:
mylib_test_source_file = """ #include <mylib.h> int main(int argc, char **argv) { MyLibrary mylib(argc, argv); return 0; } """ def CheckMyLibrary(context): context.Message('Checking for MyLibrary...') result = context.TryLink(mylib_test_source_file, '.c') context.Result(result) return result |
The Message and Result methods should typically begin and end a custom check to let the user know what's going on: the Message call prints the specified message (with no trailing newline) and the Result call prints ok if the check succeeds and failed if it doesn't. The TryLink method actually tests for whether the specified program text will successfully link.
(Note that a custom check can modify its check based on any arguments you choose to pass it, or by using or modifying the configure context environment in the context.env attribute.)
This custom check function is then attached to the configure context by passing a dictionary to the Configure call that maps a name of the check to the underlying function:
env = Environment() conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary}) |
You'll typically want to make the check and the function name the same, as we've done here, to avoid potential confusion.
We can then put these pieces together and actually call the CheckMyLibrary check as follows:
mylib_test_source_file = """ #include <mylib.h> int main(int argc, char **argv) { MyLibrary mylib(argc, argv); return 0; } """ def CheckMyLibrary(context): context.Message('Checking for MyLibrary... ') result = context.TryLink(mylib_test_source_file, '.c') context.Result(result) return result env = Environment() conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary}) if not conf.CheckMyLibrary(): print 'MyLibrary is not installed!' Exit(1) env = conf.Finish() # We would then add actual calls like Program() to build # something using the "env" construction environment. |
If MyLibrary is not installed on the system, the output will look like:
% scons scons: Reading SConscript file ... Checking for MyLibrary... failed MyLibrary is not installed! |
If MyLibrary is installed, the output will look like:
% scons scons: Reading SConscript file ... Checking for MyLibrary... failed scons: done reading SConscript scons: Building targets ... . . . |
Using multi-platform configuration as described in the previous sections will run the configuration commands even when invoking scons -c to clean targets:
% scons -Q -c Checking for MyLibrary... ok Removed foo.o Removed foo |
Although running the platform checks
when removing targets doesn't hurt anything,
it's usually unnecessary.
You can avoid this by using the
GetOption(); method to
check whether the -c
(clean)
option has been invoked on the command line:
env = Environment() if not env.GetOption('clean'): conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary}) if not conf.CheckMyLibrary(): print 'MyLibrary is not installed!' Exit(1) env = conf.Finish() |
% scons -Q -c Removed foo.o Removed foo |
On multi-developer software projects, you can sometimes speed up every developer's builds a lot by allowing them to share the derived files that they build. SCons makes this easy, as well as reliable.
To enable sharing of derived files, use the CacheDir function in any SConscript file:
CacheDir('/usr/local/build_cache') |
Note that the directory you specify must already exist and be readable and writable by all developers who will be sharing derived files. It should also be in some central location that all builds will be able to access. In environments where developers are using separate systems (like individual workstations) for builds, this directory would typically be on a shared or NFS-mounted file system.
Here's what happens: When a build has a CacheDir specified, every time a file is built, it is stored in the shared cache directory along with its MD5 build signature. [5] On subsequent builds, before an action is invoked to build a file, SCons will check the shared cache directory to see if a file with the exact same build signature already exists. If so, the derived file will not be built locally, but will be copied into the local build directory from the shared cache directory, like so:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q -c Removed hello.o Removed hello % scons -Q Retrieved `hello.o' from cache Retrieved `hello' from cache |
Note that the CacheDir feature still calculates MD5 build sigantures for the shared cache file names even if you configure SCons to use timestamps to decide if files are up to date. (See the the Chapter called Dependencies chapter for information about the Decider function.) Consequently, using CacheDir may reduce or eliminate any potential performance improvements from using timestamps for up-to-date decisions.
One potential drawback to using a shared cache is that the output printed by SCons can be inconsistent from invocation to invocation, because any given file may be rebuilt one time and retrieved from the shared cache the next time. This can make analyzing build output more difficult, especially for automated scripts that expect consistent output each time.
If, however, you use the --cache-show option, SCons will print the command line that it would have executed to build the file, even when it is retrieving the file from the shared cache. This makes the build output consistent every time the build is run:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q -c Removed hello.o Removed hello % scons -Q --cache-show cc -o hello.o -c hello.c cc -o hello hello.o |
The trade-off, of course, is that you no longer know whether or not SCons has retrieved a derived file from cache or has rebuilt it locally.
You may want to disable caching for certain specific files in your configuration. For example, if you only want to put executable files in a central cache, but not the intermediate object files, you can use the NoCache function to specify that the object files should not be cached:
env = Environment() obj = env.Object('hello.c') env.Program('hello.c') CacheDir('cache') NoCache('hello.o') |
Then when you run scons after cleaning the built targets, it will recompile the object file locally (since it doesn't exist in the shared cache directory), but still realize that the shared cache directory contains an up-to-date executable program that can be retrieved instead of re-linking:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q -c Removed hello.o Removed hello % scons -Q cc -o hello.o -c hello.c Retrieved `hello' from cache |
Retrieving an already-built file from the shared cache is usually a significant time-savings over rebuilding the file, but how much of a savings (or even whether it saves time at all) can depend a great deal on your system or network configuration. For example, retrieving cached files from a busy server over a busy network might end up being slower than rebuilding the files locally.
In these cases, you can specify the --cache-disable command-line option to tell SCons to not retrieve already-built files from the shared cache directory:
% scons -Q cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q -c Removed hello.o Removed hello % scons -Q Retrieved `hello.o' from cache Retrieved `hello' from cache % scons -Q -c Removed hello.o Removed hello % scons -Q --cache-disable cc -o hello.o -c hello.c cc -o hello hello.o |
Sometimes, you may have one or more derived files already built in your local build tree that you wish to make available to other people doing builds. For example, you may find it more effective to perform integration builds with the cache disabled (per the previous section) and only populate the shared cache directory with the built files after the integration build has completed successfully. This way, the cache will only get filled up with derived files that are part of a complete, successful build not with files that might be later overwritten while you debug integration problems.
In this case, you can use the the --cache-force option to tell SCons to put all derived files in the cache, even if the files already exist in your local tree from having been built by a previous invocation:
% scons -Q --cache-disable cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q -c Removed hello.o Removed hello % scons -Q --cache-disable cc -o hello.o -c hello.c cc -o hello hello.o % scons -Q --cache-force scons: `.' is up to date. % scons -Q scons: `.' is up to date. |
Notice how the above sample run demonstrates that the --cache-disable option avoids putting the built hello.o and hello files in the cache, but after using the --cache-force option, the files have been put in the cache for the next invocation to retrieve.
If you allow multiple builds to update the shared cache directory simultaneously, two builds that occur at the same time can sometimes start "racing" with one another to build the same files in the same order. If, for example, you are linking multiple files into an executable program:
Program('prog', ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c']) |
SCons will normally build the input object files on which the program depends in their normal, sorted order:
% scons -Q cc -o f1.o -c f1.c cc -o f2.o -c f2.c cc -o f3.o -c f3.c cc -o f4.o -c f4.c cc -o f5.o -c f5.c cc -o prog f1.o f2.o f3.o f4.o f5.o |
But if two such builds take place simultaneously, they may each look in the cache at nearly the same time and both decide that f1.o must be rebuilt and pushed into the shared cache directory, then both decide that f2.o must be rebuilt (and pushed into the shared cache directory), then both decide that f3.o must be rebuilt... This won't cause any actual build problems--both builds will succeed, generate correct output files, and populate the cache--but it does represent wasted effort.
To alleviate such contention for the cache, you can use the --random command-line option to tell SCons to build dependencies in a random order:
% scons -Q --random cc -o f3.o -c f3.c cc -o f1.o -c f1.c cc -o f5.o -c f5.c cc -o f2.o -c f2.c cc -o f4.o -c f4.c cc -o prog f1.o f2.o f3.o f4.o f5.o |
Multiple builds using the --random option will usually build their dependencies in different, random orders, which minimizes the chances for a lot of contention for same-named files in the shared cache directory. Multiple simultaneous builds might still race to try to build the same target file on occasion, but long sequences of inefficient contention should be rare.
Note, of course, the --random option will cause the output that SCons prints to be inconsistent from invocation to invocation, which may be an issue when trying to compare output from different build runs.
If you want to make sure dependencies will be built in a random order without having to specify the --random on very command line, you can use the SetOption function to set the random option within any SConscript file:
Program('prog', ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c']) SetOption('random', 1) Program('prog', ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c']) |
We've already seen how you can use the Alias function to create a target named install:
env = Environment() hello = env.Program('hello.c') env.Install('/usr/bin', hello) env.Alias('install', '/usr/bin') |
You can then use this alias on the command line to tell SCons more naturally that you want to install files:
% scons -Q install cc -o hello.o -c hello.c cc -o hello hello.o Install file: "hello" as "/usr/bin/hello" |
Like other Builder
methods, though,
the Alias method returns an object
representing the alias being built.
You can then use this object as input to anothother Builder
.
This is especially useful if you use such an object
as input to another call to the Alias Builder
,
allowing you to create a hierarchy
of nested aliases:
env = Environment() p = env.Program('foo.c') l = env.Library('bar.c') env.Install('/usr/bin', p) env.Install('/usr/lib', l) ib = env.Alias('install-bin', '/usr/bin') il = env.Alias('install-lib', '/usr/lib') env.Alias('install', [ib, il]) |
This example defines separate install, install-bin, and install-lib aliases, allowing you finer control over what gets installed:
% scons -Q install-bin cc -o foo.o -c foo.c cc -o foo foo.o Install file: "foo" as "/usr/bin/foo" % scons -Q install-lib cc -o bar.o -c bar.c ar rc libbar.a bar.o ranlib libbar.a Install file: "libbar.a" as "/usr/lib/libbar.a" % scons -Q -c / Removed foo.o Removed foo Removed /usr/bin/foo Removed bar.o Removed libbar.a Removed /usr/lib/libbar.a % scons -Q install cc -o foo.o -c foo.c cc -o foo foo.o Install file: "foo" as "/usr/bin/foo" cc -o bar.o -c bar.c ar rc libbar.a bar.o ranlib libbar.a Install file: "libbar.a" as "/usr/lib/libbar.a" |
So far, we've been using examples of building C and C++ programs to demonstrate the features of SCons. SCons also supports building Java programs, but Java builds are handled slightly differently, which reflects the ways in which the Java compiler and tools build programs differently than other languages' tool chains.
The basic activity when programming in Java, of course, is to take one or more .java files containing Java source code and to call the Java compiler to turn them into one or more .class files. In SCons, you do this by giving the Java Builder a target directory in which to put the .class files, and a source directory that contains the .java files:
Java('classes', 'src') |
If the src directory contains three .java source files, then running SCons might look like this:
% scons -Q javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java |
SCons will actually search the src directory tree for all of the .java files. The Java compiler will then create the necessary class files in the classes subdirectory, based on the class names found in the .java files.
In addition to searching the source directory for .java files, SCons actually runs the .java files through a stripped-down Java parser that figures out what classes are defined. In other words, SCons knows, without you having to tell it, what .class files will be produced by the javac call. So our one-liner example from the preceding section:
Java('classes', 'src') |
Will not only tell you reliably that the .class files in the classes subdirectory are up-to-date:
% scons -Q javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java % scons -Q classes scons: `classes' is up to date. |
But it will also remove all of the generated .class files, even for inner classes, without you having to specify them manually. For example, if our Example1.java and Example3.java files both define additional classes, and the class defined in Example2.java has an inner class, running scons -c will clean up all of those .class files as well:
% scons -Q javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java % scons -Q -c classes Removed classes/Example1.class Removed classes/AdditionalClass1.class Removed classes/Example2$Inner2.class Removed classes/Example2.class Removed classes/Example3.class Removed classes/AdditionalClass3.class |
After building the class files, it's common to collect them into a Java archive (.jar) file, which you do by calling the Jar Builder method. If you want to just collect all of the class files within a subdirectory, you can just specify that subdirectory as the Jar source:
Java(target = 'classes', source = 'src') Jar(target = 'test.jar', source = 'classes') |
SCons will then pass that directory to the jar command, which will collect all of the underlying .class files:
% scons -Q javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java jar cf test.jar classes |
If you want to keep all of the .class files for multiple programs in one location, and only archive some of them in each .jar file, you can pass the Jar builder a list of files as its source. It's extremely simple to create multiple .jar files this way, using the lists of target class files created by calls to the Java builder as sources to the various Jar calls:
prog1_class_files = Java(target = 'classes', source = 'prog1') prog2_class_files = Java(target = 'classes', source = 'prog2') Jar(target = 'prog1.jar', source = prog1_class_files) Jar(target = 'prog2.jar', source = prog2_class_files) |
This will then create prog1.jar and prog2.jar next to the subdirectories that contain their .java files:
% scons -Q javac -d classes -sourcepath prog1 prog1/Example1.java prog1/Example2.java javac -d classes -sourcepath prog2 prog2/Example3.java prog2/Example4.java jar cf prog1.jar -C classes Example1.class -C classes Example2.class jar cf prog2.jar -C classes Example3.class -C classes Example4.class |
You can generate C header and source files for implementing native methods, by using the JavaH Builder. There are several ways of using the JavaH Builder. One typical invocation might look like:
classes = Java(target = 'classes', source = 'src/pkg/sub') JavaH(target = 'native', source = classes) |
The source is a list of class files generated by the
call to the Java Builder,
and the target is the output directory in
which we want the C header files placed.
The target
gets converted into the -d
when SCons runs javah:
% scons -Q javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java javah -d native -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3 |
In this case,
the call to javah
will generate the header files
native/pkg_sub_Example1.h,
native/pkg_sub_Example2.h
and
native/pkg_sub_Example3.h.
Notice that SCons remembered that the class
files were generated with a target directory of
classes,
and that it then specified that target directory
as the -classpath
option
to the call to javah.
Although it's more convenient to use
the list of class files returned by
the Java Builder
as the source of a call to the JavaH Builder,
you can
specify the list of class files
by hand, if you prefer.
If you do,
you need to set the
$JAVACLASSDIR
construction variable
when calling JavaH:
Java(target = 'classes', source = 'src/pkg/sub') class_file_list = ['classes/pkg/sub/Example1.class', 'classes/pkg/sub/Example2.class', 'classes/pkg/sub/Example3.class'] JavaH(target = 'native', source = class_file_list, JAVACLASSDIR = 'classes') |
The $JAVACLASSDIR
value then
gets converted into the -classpath
when SCons runs javah:
% scons -Q javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java javah -d native -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3 |
Lastly, if you don't want a separate header file generated for each source file, you can specify an explicit File Node as the target of the JavaH Builder:
classes = Java(target = 'classes', source = 'src/pkg/sub') JavaH(target = File('native.h'), source = classes) |
Because SCons assumes by default
that the target of the JavaH builder is a directory,
you need to use the File function
to make sure that SCons doesn't
create a directory named native.h.
When a file is used, though,
SCons correctly converts the file name
into the javah -o
option:
% scons -Q javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java javah -o native.h -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3 |
You can generate Remote Method Invocation stubs by using the RMIC Builder. The source is a list of directories, typically returned by a call to the Java Builder, and the target is an output directory where the _Stub.class and _Skel.class files will be placed:
classes = Java(target = 'classes', source = 'src/pkg/sub') RMIC(target = 'outdir', source = classes) |
As it did with the JavaH Builder,
SCons remembers the class directory
and passes it as the -classpath
option
to rmic:
% scons -Q javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java rmic -d outdir -classpath classes pkg.sub.Example1 pkg.sub.Example2 |
This example would generate the files outdir/pkg/sub/Example1_Skel.class, outdir/pkg/sub/Example1_Stub.class, outdir/pkg/sub/Example2_Skel.class and outdir/pkg/sub/Example2_Stub.class.
SCons supports a lot of additional functionality that doesn't readily fit into the other chapters.
Although the SCons code itself will run on any Python version 1.5.2 or later, you are perfectly free to make use of Python syntax and modules from more modern versions (for example, Python 2.4 or 2.5) when writing your SConscript files or your own local modules. If you do this, it's usually helpful to configure SCons to exit gracefully with an error message if it's being run with a version of Python that simply won't work with your code. This is especially true if you're going to use SCons to build source code that you plan to distribute publicly, where you can't be sure of the Python version that an anonymous remote user might use to try to build your software.
SCons provides an EnsurePythonVersion function for this. You simply pass it the major and minor versions numbers of the version of Python you require:
EnsurePythonVersion(2, 5) |
And then SCons will exit with the following error message when a user runs it with an unsupported earlier version of Python:
% scons -Q Python 2.5 or greater required, but you have Python 2.3.6 |
You may, of course, write your SConscript files to use features that were only added in recent versions of SCons. When you publicly distribute software that is built using SCons, it's helpful to have SCons verify the version being used and exit gracefully with an error message if the user's version of SCons won't work with your SConscript files. SCons provides an EnsureSConsVersion function that verifies the version of SCons in the same the EnsurePythonVersion function verifies the version of Python, by passing in the major and minor versions numbers of the version of SCons you require:
EnsureSConsVersion(1, 0) |
And then SCons will exit with the following error message when a user runs it with an unsupported earlier version of SCons:
% scons -Q SCons 1.0 or greater required, but you have SCons 0.98.5 |
SCons supports an Exit function which can be used to terminate SCons while reading the SConscript files, usually because you've detected a condition under which it doesn't make sense to proceed:
if ARGUMENTS.get('FUTURE'): print "The FUTURE option is not supported yet!" Exit(2) env = Environment() env.Program('hello.c') |
% scons -Q FUTURE=1 The FUTURE option is not supported yet! % scons -Q cc -o hello.o -c hello.c cc -o hello hello.o |
The Exit function takes as an argument the (numeric) exit status that you want SCons to exit with. If you don't specify a value, the default is to exit with 0, which indicates successful execution.
Note that the Exit function is equivalent to calling the Python sys.exit function (which the it actually calls), but because Exit is a SCons function, you don't have to import the Python sys module to use it.
The FindFile function searches for a file in a list of directories. If there is only one directory, it can be given as a simple string. The function returns a File node if a matching file exists, or None if no file is found. (See the documentation for the Glob function for an alternative way of searching for entries in a directory.)
# one directory print FindFile('missing', '.') t = FindFile('exists', '.') print t.__class__, t |
% scons -Q None SCons.Node.FS.File exists scons: `.' is up to date. |
# several directories includes = [ '.', 'include', 'src/include'] headers = [ 'nonesuch.h', 'config.h', 'private.h', 'dist.h'] for hdr in headers: print '%-12s' % ('%s:' % hdr), FindFile(hdr, includes) |
% scons -Q nonesuch.h: None config.h: config.h private.h: src/include/private.h dist.h: include/dist.h scons: `.' is up to date. |
If the file exists in more than one directory, only the first occurrence is returned.
print FindFile('multiple', ['sub1', 'sub2', 'sub3']) print FindFile('multiple', ['sub2', 'sub3', 'sub1']) print FindFile('multiple', ['sub3', 'sub1', 'sub2']) |
% scons -Q sub1/multiple sub2/multiple sub3/multiple scons: `.' is up to date. |
In addition to existing files, FindFile will also find derived files (that is, non-leaf files) that haven't been built yet. (Leaf files should already exist, or the build will fail!)
# Neither file exists, so build will fail Command('derived', 'leaf', 'cat >$TARGET $SOURCE') print FindFile('leaf', '.') print FindFile('derived', '.') |
% scons -Q None derived scons: *** Source `leaf' not found, needed by target `derived'. Stop. |
# Neither file exists, so build will fail Command('derived', 'leaf', 'cat >$TARGET $SOURCE') print FindFile('leaf', '.') print FindFile('derived', '.') # Only 'leaf' exists Command('derived', 'leaf', 'cat >$TARGET $SOURCE') print FindFile('leaf', '.') print FindFile('derived', '.') |
% scons -Q leaf derived cat > derived leaf |
If a source file exists, FindFile will correctly return the name in the build directory.
# Only 'src/leaf' exists VariantDir('build', 'src') print FindFile('leaf', 'build') |
% scons -Q build/leaf scons: `.' is up to date. |
SCons supports a Flatten function which takes an input Python sequence (list or tuple) and returns a flattened list containing just the individual elements of the sequence. This can be handy when trying to examine a list composed of the lists returned by calls to various Builders. For example, you might collect object files built in different ways into one call to the Program Builder by just enclosing them in a list, as follows:
objects = [ Object('prog1.c'), Object('prog2.c', CCFLAGS='-DFOO'), ] Program(objects) |
Because the Builder calls in SCons flatten their input lists, this works just fine to build the program:
% scons -Q cc -o prog1.o -c prog1.c cc -o prog2.o -c -DFOO prog2.c cc -o prog1 prog1.o prog2.o |
But if you were debugging your build
and wanted to print the absolute path
of each object file in the
objects
list,
you might try the following simple approach,
trying to print each Node's
abspath
attribute:
objects = [ Object('prog1.c'), Object('prog2.c', CCFLAGS='-DFOO'), ] Program(objects) for object_file in objects: print object_file.abspath |
This does not work as expected because each call to str is operating an embedded list returned by each Object call, not on the underlying Nodes within those lists:
% scons -Q AttributeError: NodeList instance has no attribute 'abspath': File "/home/my/project/SConstruct", line 8: print object_file.abspath |
The solution is to use the Flatten function so that you can pass each Node to the str separately:
objects = [ Object('prog1.c'), Object('prog2.c', CCFLAGS='-DFOO'), ] Program(objects) for object_file in Flatten(objects): print object_file.abspath |
% scons -Q /home/me/project/prog1.o /home/me/project/prog2.o cc -o prog1.o -c prog1.c cc -o prog2.o -c -DFOO prog2.c cc -o prog1 prog1.o prog2.o |
If you need to find the directory from which the user invoked the scons command, you can use the GetLaunchDir function:
env = Environment( LAUNCHDIR = GetLaunchDir(), ) env.Command('directory_build_info', '$LAUNCHDIR/build_info' Copy('$TARGET', '$SOURCE')) |
Because SCons is usually invoked from the top-level directory in which the SConstruct file lives, the Python os.getcwd() is often equivalent. However, the SCons -u, -U and -D command-line options, when invoked from a subdirectory, will cause SCons to change to the directory in which the SConstruct file is found. When those options are used, GetLaunchDir will still return the path to the user's invoking subdirectory, allowing the SConscript configuration to still get at configuration (or other) files from the originating directory.
The experience of configuring any software build tool to build a large code base usually, at some point, involves trying to figure out why the tool is behaving a certain way, and how to get it to behave the way you want. SCons is no different. This appendix contains a number of different ways in which you can get some additional insight into SCons' behavior.
Note that we're always interested in trying to improve how you can troubleshoot configuration problems. If you run into a problem that has you scratching your head, and which there just doesn't seem to be a good way to debug, odds are pretty good that someone else will run into the same problem, too. If so, please let the SCons development team know (preferably by filing a bug report or feature request at our project pages at tigris.org) so that we can use your feedback to try to come up with a better way to help you, and others, get the necessary insight into SCons behavior to help identify and fix configuration issues.
Let's look at a simple example of a misconfigured build that causes a target to be rebuilt every time SCons is run:
# Intentionally misspell the output file name in the # command used to create the file: Command('file.out', 'file.in', 'cp $SOURCE file.oout') |
(Note to Windows users: The POSIX cp command copies the first file named on the command line to the second file. In our example, it copies the file.in file to the file.out file.)
Now if we run SCons multiple times on this example, we see that it re-runs the cp command every time:
% scons -Q cp file.in file.oout % scons -Q cp file.in file.oout % scons -Q cp file.in file.oout |
In this example, the underlying cause is obvious: we've intentionally misspelled the output file name in the cp command, so the command doesn't actually build the file.out file that we've told SCons to expect. But if the problem weren't obvious, it would be helpful to specify the --debug=explain option on the command line to have SCons tell us very specifically why it's decided to rebuild the target:
% scons -Q --debug=explain scons: building `file.out' because it doesn't exist cp file.in file.oout |
If this had been a more complicated example involving a lot of build output, having SCons tell us that it's trying to rebuild the target file because it doesn't exist would be an important clue that something was wrong with the command that we invoked to build it.
The --debug=explain option also comes in handy to help figure out what input file changed. Given a simple configuration that builds a program from three source files, changing one of the source files and rebuilding with the --debug=explain option shows very specifically why SCons rebuilds the files that it does:
% scons -Q cc -o file1.o -c file1.c cc -o file2.o -c file2.c cc -o file3.o -c file3.c cc -o prog file1.o file2.o file3.o % edit file2.c [CHANGE THE CONTENTS OF file2.c] % scons -Q --debug=explain scons: rebuilding `file2.o' because `file2.c' changed cc -o file2.o -c file2.c scons: rebuilding `prog' because `file2.o' changed cc -o prog file1.o file2.o file3.o |
This becomes even more helpful in identifying when a file is rebuilt due to a change in an implicit dependency, such as an incuded .h file. If the file1.c and file3.c files in our example both included a hello.h file, then changing that included file and re-running SCons with the --debug=explain option will pinpoint that it's the change to the included file that starts the chain of rebuilds:
% scons -Q cc -o file1.o -c -I. file1.c cc -o file2.o -c -I. file2.c cc -o file3.o -c -I. file3.c cc -o prog file1.o file2.o file3.o % edit hello.h [CHANGE THE CONTENTS OF hello.h] % scons -Q --debug=explain scons: rebuilding `file1.o' because `hello.h' changed cc -o file1.o -c -I. file1.c scons: rebuilding `file3.o' because `hello.h' changed cc -o file3.o -c -I. file3.c scons: rebuilding `prog' because: `file1.o' changed `file3.o' changed cc -o prog file1.o file2.o file3.o |
(Note that the --debug=explain option will only tell you why SCons decided to rebuild necessary targets. It does not tell you what files it examined when deciding not to rebuild a target file, which is often a more valuable question to answer.)
When you create a construction environment, SCons populates it with construction variables that are set up for various compilers, linkers and utilities that it finds on your system. Although this is usually helpful and what you want, it might be frustrating if SCons doesn't set certain variables that you expect to be set. In situations like this, it's sometimes helpful to use the construction environment Dump method to print all or some of the construction variables. Note that the Dump method returns the representation of the variables in the environment for you to print (or otherwise manipulate):
env = Environment() print env.Dump() |
On a POSIX system with gcc installed, this might generate:
% scons scons: Reading SConscript files ... { 'BUILDERS': {'_InternalInstall': <function InstallBuilderWrapper at 0x700000>, '_InternalInstallAs': <function InstallAsBuilderWrapper at 0x700000>}, 'CONFIGUREDIR': '#/.sconf_temp', 'CONFIGURELOG': '#/config.log', 'CPPSUFFIXES': [ '.c', '.C', '.cxx', '.cpp', '.c++', '.cc', '.h', '.H', '.hxx', '.hpp', '.hh', '.F', '.fpp', '.FPP', '.m', '.mm', '.S', '.spp', '.SPP'], 'DSUFFIXES': ['.d'], 'Dir': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'Dirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'ENV': {'PATH': '/usr/local/bin:/opt/bin:/bin:/usr/bin'}, 'ESCAPE': <function escape at 0x700000>, 'File': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'IDLSUFFIXES': ['.idl', '.IDL'], 'INSTALL': <function copyFunc at 0x700000>, 'LATEXSUFFIXES': ['.tex', '.ltx', '.latex'], 'LIBPREFIX': 'lib', 'LIBPREFIXES': ['$LIBPREFIX'], 'LIBSUFFIX': '.a', 'LIBSUFFIXES': ['$LIBSUFFIX', '$SHLIBSUFFIX'], 'MAXLINELENGTH': 128072, 'OBJPREFIX': '', 'OBJSUFFIX': '.o', 'PLATFORM': 'posix', 'PROGPREFIX': '', 'PROGSUFFIX': '', 'PSPAWN': <function piped_env_spawn at 0x700000>, 'RDirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'SCANNERS': [], 'SHELL': 'sh', 'SHLIBPREFIX': '$LIBPREFIX', 'SHLIBSUFFIX': '.so', 'SHOBJPREFIX': '$OBJPREFIX', 'SHOBJSUFFIX': '$OBJSUFFIX', 'SPAWN': <function spawnvpe_spawn at 0x700000>, 'TEMPFILE': <class SCons.Platform.TempFileMunge at 0x700000>, 'TEMPFILEPREFIX': '@', 'TOOLS': ['install', 'install'], '_CPPDEFFLAGS': '${_defines(CPPDEFPREFIX, CPPDEFINES, CPPDEFSUFFIX, __env__)}', '_CPPINCFLAGS': '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)', '_LIBDIRFLAGS': '$( ${_concat(LIBDIRPREFIX, LIBPATH, LIBDIRSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)', '_LIBFLAGS': '${_concat(LIBLINKPREFIX, LIBS, LIBLINKSUFFIX, __env__)}', '__RPATH': '$_RPATH', '_concat': <function _concat at 0x700000>, '_defines': <function _defines at 0x700000>, '_stripixes': <function _stripixes at 0x700000>} scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets. |
On a Windows system with Visual C++ the output might look like:
C:\>scons scons: Reading SConscript files ... { 'BUILDERS': {'_InternalInstall': <function InstallBuilderWrapper at 0x700000>, 'Object': <SCons.Builder.CompositeBuilder instance at 0x700000>, 'PCH': <SCons.Builder.BuilderBase instance at 0x700000>, 'RES': <SCons.Builder.BuilderBase instance at 0x700000>, 'SharedObject': <SCons.Builder.CompositeBuilder instance at 0x700000>, 'StaticObject': <SCons.Builder.CompositeBuilder instance at 0x700000>, '_InternalInstallAs': <function InstallAsBuilderWrapper at 0x700000>}, 'CC': 'cl', 'CCCOM': <SCons.Action.FunctionAction instance at 0x700000>, 'CCFLAGS': ['/nologo'], 'CCPCHFLAGS': ['${(PCH and "/Yu%s /Fp%s"%(PCHSTOP or "",File(PCH))) or ""}'], 'CCPDBFLAGS': ['${(PDB and "/Z7") or ""}'], 'CFILESUFFIX': '.c', 'CFLAGS': [], 'CONFIGUREDIR': '#/.sconf_temp', 'CONFIGURELOG': '#/config.log', 'CPPDEFPREFIX': '/D', 'CPPDEFSUFFIX': '', 'CPPSUFFIXES': [ '.c', '.C', '.cxx', '.cpp', '.c++', '.cc', '.h', '.H', '.hxx', '.hpp', '.hh', '.F', '.fpp', '.FPP', '.m', '.mm', '.S', '.spp', '.SPP'], 'CXX': '$CC', 'CXXCOM': '$CXX /Fo$TARGET /c $SOURCES $CXXFLAGS $CCFLAGS $_CCCOMCOM', 'CXXFILESUFFIX': '.cc', 'CXXFLAGS': ['$CCFLAGS', '$(', '/TP', '$)'], 'DSUFFIXES': ['.d'], 'Dir': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'Dirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'ENV': { 'INCLUDE': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\include', 'LIB': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\lib', 'PATH': 'C:\\Program Files\\Microsoft Visual Studio\\Common\\tools\\WIN95;C:\\Program Files\\Microsoft Visual Studio\\Common\\MSDev98\\bin;C:\\Program Files\\Microsoft Visual Studio\\Common\\tools;C:\\Program Files\\Microsoft Visual Studio/VC98\\bin', 'PATHEXT': '.COM;.EXE;.BAT;.CMD', 'SystemRoot': 'C:/WINDOWS'}, 'ESCAPE': <function escape at 0x700000>, 'File': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'IDLSUFFIXES': ['.idl', '.IDL'], 'INCPREFIX': '/I', 'INCSUFFIX': '', 'INSTALL': <function copyFunc at 0x700000>, 'LATEXSUFFIXES': ['.tex', '.ltx', '.latex'], 'LIBPREFIX': '', 'LIBPREFIXES': ['$LIBPREFIX'], 'LIBSUFFIX': '.lib', 'LIBSUFFIXES': ['$LIBSUFFIX'], 'MAXLINELENGTH': 2048, 'MSVS': {'VERSION': '6.0', 'VERSIONS': ['6.0']}, 'MSVS_VERSION': '6.0', 'OBJPREFIX': '', 'OBJSUFFIX': '.obj', 'PCHCOM': '$CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS /c $SOURCES /Fo${TARGETS[1]} /Yc$PCHSTOP /Fp${TARGETS[0]} $CCPDBFLAGS $PCHPDBFLAGS', 'PCHPDBFLAGS': ['${(PDB and "/Yd") or ""}'], 'PLATFORM': 'win32', 'PROGPREFIX': '', 'PROGSUFFIX': '.exe', 'PSPAWN': <function piped_spawn at 0x700000>, 'RC': 'rc', 'RCCOM': <SCons.Action.FunctionAction instance at 0x700000>, 'RCFLAGS': [], 'RCSUFFIXES': ['.rc', '.rc2'], 'RDirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>, 'SCANNERS': [], 'SHCC': '$CC', 'SHCCCOM': <SCons.Action.FunctionAction instance at 0x700000>, 'SHCCFLAGS': ['$CCFLAGS'], 'SHCFLAGS': ['$CFLAGS'], 'SHCXX': '$CXX', 'SHCXXCOM': '$SHCXX /Fo$TARGET /c $SOURCES $SHCXXFLAGS $SHCCFLAGS $_CCCOMCOM', 'SHCXXFLAGS': ['$CXXFLAGS'], 'SHELL': None, 'SHLIBPREFIX': '', 'SHLIBSUFFIX': '.dll', 'SHOBJPREFIX': '$OBJPREFIX', 'SHOBJSUFFIX': '$OBJSUFFIX', 'SPAWN': <function spawn at 0x700000>, 'STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME': 1, 'TEMPFILE': <class SCons.Platform.TempFileMunge at 0x700000>, 'TEMPFILEPREFIX': '@', 'TOOLS': ['msvc', 'install', 'install'], '_CCCOMCOM': '$CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS $CCPCHFLAGS $CCPDBFLAGS', '_CPPDEFFLAGS': '${_defines(CPPDEFPREFIX, CPPDEFINES, CPPDEFSUFFIX, __env__)}', '_CPPINCFLAGS': '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)', '_LIBDIRFLAGS': '$( ${_concat(LIBDIRPREFIX, LIBPATH, LIBDIRSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)', '_LIBFLAGS': '${_concat(LIBLINKPREFIX, LIBS, LIBLINKSUFFIX, __env__)}', '_concat': <function _concat at 0x700000>, '_defines': <function _defines at 0x700000>, '_stripixes': <function _stripixes at 0x700000>} scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets. |
The construction environments in these examples have actually been restricted to just gcc and Visual C++, respectively. In a real-life situation, the construction environments will likely contain a great many more variables. Also note that we've massaged the example output above to make the memory address of all objects a constant 0x700000. In reality, you would see a different hexadecimal number for each object.
To make it easier to see just what you're interested in, the Dump method allows you to specify a specific constrcution variable that you want to disply. For example, it's not unusual to want to verify the external environment used to execute build commands, to make sure that the PATH and other environment variables are set up the way they should be. You can do this as follows:
env = Environment() print env.Dump('ENV') |
Which might display the following when executed on a POSIX system:
% scons scons: Reading SConscript files ... {'PATH': '/usr/local/bin:/opt/bin:/bin:/usr/bin'} scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets. |
And the following when executed on a Windows system:
C:\>scons scons: Reading SConscript files ... { 'INCLUDE': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\include', 'LIB': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\lib', 'PATH': 'C:\\Program Files\\Microsoft Visual Studio\\Common\\tools\\WIN95;C:\\Program Files\\Microsoft Visual Studio\\Common\\MSDev98\\bin;C:\\Program Files\\Microsoft Visual Studio\\Common\\tools;C:\\Program Files\\Microsoft Visual Studio/VC98\\bin', 'PATHEXT': '.COM;.EXE;.BAT;.CMD', 'SystemRoot': 'C:/WINDOWS'} scons: done reading SConscript files. scons: Building targets ... scons: `.' is up to date. scons: done building targets. |
Sometimes the best way to try to figure out what SCons is doing is simply to take a look at the dependency graph that it constructs based on your SConscript files. The --tree option will display all or part of the SCons dependency graph in an "ASCII art" graphical format that shows the dependency hierarchy.
For example, given the following input SConstruct file:
env = Environment(CPPPATH = ['.']) env.Program('prog', ['f1.c', 'f2.c', 'f3.c']) |
Running SCons with the --tree=all option yields:
% scons -Q --tree=all cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c cc -o prog f1.o f2.o f3.o +-. +-SConstruct +-f1.c +-f1.o | +-f1.c | +-inc.h +-f2.c +-f2.o | +-f2.c | +-inc.h +-f3.c +-f3.o | +-f3.c | +-inc.h +-inc.h +-prog +-f1.o | +-f1.c | +-inc.h +-f2.o | +-f2.c | +-inc.h +-f3.o +-f3.c +-inc.h |
The tree will also be printed when the -n (no execute) option is used, which allows you to examine the dependency graph for a configuration without actually rebuilding anything in the tree.
The --tree option only prints the dependency graph for the specified targets (or the default target(s) if none are specified on the command line). So if you specify a target like f2.o on the command line, the --tree option will only print the dependency graph for that file:
% scons -Q --tree=all f2.o cc -o f2.o -c -I. f2.c +-f2.o +-f2.c +-inc.h |
This is, of course, useful for restricting the output from a very large build configuration to just a portion in which you're interested. Multiple targets are fine, in which case a tree will be printed for each specified target:
% scons -Q --tree=all f1.o f3.o cc -o f1.o -c -I. f1.c +-f1.o +-f1.c +-inc.h cc -o f3.o -c -I. f3.c +-f3.o +-f3.c +-inc.h |
The status argument may be used to tell SCons to print status information about each file in the dependency graph:
% scons -Q --tree=status cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c cc -o prog f1.o f2.o f3.o E = exists R = exists in repository only b = implicit builder B = explicit builder S = side effect P = precious A = always build C = current N = no clean H = no cache [E b ]+-. [E C ] +-SConstruct [E C ] +-f1.c [E B C ] +-f1.o [E C ] | +-f1.c [E C ] | +-inc.h [E C ] +-f2.c [E B C ] +-f2.o [E C ] | +-f2.c [E C ] | +-inc.h [E C ] +-f3.c [E B C ] +-f3.o [E C ] | +-f3.c [E C ] | +-inc.h [E C ] +-inc.h [E B C ] +-prog [E B C ] +-f1.o [E C ] | +-f1.c [E C ] | +-inc.h [E B C ] +-f2.o [E C ] | +-f2.c [E C ] | +-inc.h [E B C ] +-f3.o [E C ] +-f3.c [E C ] +-inc.h |
Note that --tree=all,status is equivalent; the all is assumed if only status is present. As an alternative to all, you can specify --tree=derived to have SCons only print derived targets in the tree output, skipping source files (like .c and .h files):
% scons -Q --tree=derived cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c cc -o prog f1.o f2.o f3.o +-. +-f1.o +-f2.o +-f3.o +-prog +-f1.o +-f2.o +-f3.o |
You can use the status modifier with derived as well:
% scons -Q --tree=derived,status cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c cc -o prog f1.o f2.o f3.o E = exists R = exists in repository only b = implicit builder B = explicit builder S = side effect P = precious A = always build C = current N = no clean H = no cache [E b ]+-. [E B C ] +-f1.o [E B C ] +-f2.o [E B C ] +-f3.o [E B C ] +-prog [E B C ] +-f1.o [E B C ] +-f2.o [E B C ] +-f3.o |
Note that the order of the --tree= arguments doesn't matter; --tree=status,derived is completely equivalent.
The default behavior of the --tree option is to repeat all of the dependencies each time the library dependency (or any other dependency file) is encountered in the tree. If certain target files share other target files, such as two programs that use the same library:
env = Environment(CPPPATH = ['.'], LIBS = ['foo'], LIBPATH = ['.']) env.Library('foo', ['f1.c', 'f2.c', 'f3.c']) env.Program('prog1.c') env.Program('prog2.c') |
Then there can be a lot of repetition in the --tree= output:
% scons -Q --tree=all cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c ar rc libfoo.a f1.o f2.o f3.o ranlib libfoo.a cc -o prog1.o -c -I. prog1.c cc -o prog1 prog1.o -L. -lfoo cc -o prog2.o -c -I. prog2.c cc -o prog2 prog2.o -L. -lfoo +-. +-SConstruct +-f1.c +-f1.o | +-f1.c | +-inc.h +-f2.c +-f2.o | +-f2.c | +-inc.h +-f3.c +-f3.o | +-f3.c | +-inc.h +-inc.h +-libfoo.a | +-f1.o | | +-f1.c | | +-inc.h | +-f2.o | | +-f2.c | | +-inc.h | +-f3.o | +-f3.c | +-inc.h +-prog1 | +-prog1.o | | +-prog1.c | | +-inc.h | +-libfoo.a | +-f1.o | | +-f1.c | | +-inc.h | +-f2.o | | +-f2.c | | +-inc.h | +-f3.o | +-f3.c | +-inc.h +-prog1.c +-prog1.o | +-prog1.c | +-inc.h +-prog2 | +-prog2.o | | +-prog2.c | | +-inc.h | +-libfoo.a | +-f1.o | | +-f1.c | | +-inc.h | +-f2.o | | +-f2.c | | +-inc.h | +-f3.o | +-f3.c | +-inc.h +-prog2.c +-prog2.o +-prog2.c +-inc.h |
In a large configuration with many internal libraries and include files, this can very quickly lead to huge output trees. To help make this more manageable, a prune modifier may be added to the option list, in which case SCons will print the name of a target that has already been visited during the tree-printing in [square brackets] as an indication that the dependencies of the target file may be found by looking farther up the tree:
% scons -Q --tree=prune cc -o f1.o -c -I. f1.c cc -o f2.o -c -I. f2.c cc -o f3.o -c -I. f3.c ar rc libfoo.a f1.o f2.o f3.o ranlib libfoo.a cc -o prog1.o -c -I. prog1.c cc -o prog1 prog1.o -L. -lfoo cc -o prog2.o -c -I. prog2.c cc -o prog2 prog2.o -L. -lfoo +-. +-SConstruct +-f1.c +-f1.o | +-f1.c | +-inc.h +-f2.c +-f2.o | +-f2.c | +-inc.h +-f3.c +-f3.o | +-f3.c | +-inc.h +-inc.h +-libfoo.a | +-[f1.o] | +-[f2.o] | +-[f3.o] +-prog1 | +-prog1.o | | +-prog1.c | | +-inc.h | +-[libfoo.a] +-prog1.c +-[prog1.o] +-prog2 | +-prog2.o | | +-prog2.c | | +-inc.h | +-[libfoo.a] +-prog2.c +-[prog2.o] |
Like the status keyword, the prune argument by itself is equivalent to --tree=all,prune.
Sometimes it's useful to look at the pre-substitution string that SCons uses to generate the command lines it executes. This can be done with the --debug=presub option:
% scons -Q --debug=presub Building prog.o with action: $CC -o $TARGET -c $CFLAGS $CCFLAGS $_CCOMCOM $SOURCES cc -o prog.o -c -I. prog.c Building prog with action: $SMART_LINKCOM cc -o prog prog.o |
To get some insight into what library names SCons is searching for, and in which directories it is searching, Use the --debug=findlibs option. Given the following input SConstruct file:
env = Environment(LIBPATH = ['libs1', 'libs2']) env.Program('prog.c', LIBS=['foo', 'bar']) |
And the libraries libfoo.a and libbar.a in libs1 and libs2, respectively, use of the --debug=findlibs option yields:
% scons -Q --debug=findlibs findlibs: looking for 'libfoo.a' in 'libs1' ... findlibs: ... FOUND 'libfoo.a' in 'libs1' findlibs: looking for 'libfoo.so' in 'libs1' ... findlibs: looking for 'libfoo.so' in 'libs2' ... findlibs: looking for 'libbar.a' in 'libs1' ... findlibs: looking for 'libbar.a' in 'libs2' ... findlibs: ... FOUND 'libbar.a' in 'libs2' findlibs: looking for 'libbar.so' in 'libs1' ... findlibs: looking for 'libbar.so' in 'libs2' ... cc -o prog.o -c prog.c cc -o prog prog.o -Llibs1 -Llibs2 -lfoo -lbar |
In general, SCons tries to keep its error messages short and informative. That means we usually try to avoid showing the stack traces that are familiar to experienced Python programmers, since they usually contain much more information than is useful to most people.
For example, the following SConstruct file:
Program('prog.c') |
Generates the following error if the prog.c file does not exist:
% scons -Q scons: *** Source `prog.c' not found, needed by target `prog.o'. Stop. |
In this case, the error is pretty obvious. But if it weren't, and you wanted to try to get more information about the error, the --debug=stacktrace option would show you exactly where in the SCons source code the problem occurs:
% scons -Q --debug=stacktrace scons: *** Source `prog.c' not found, needed by target `prog.o'. Stop. scons: internal stack trace: File "bootstrap/src/engine/SCons/Job.py", line 197, in start File "bootstrap/src/engine/SCons/Script/Main.py", line 167, in prepare File "bootstrap/src/engine/SCons/Taskmaster.py", line 182, in prepare File "bootstrap/src/engine/SCons/Executor.py", line 171, in prepare |
Of course, if you do need to dive into the SCons source code, we'd like to know if, or how, the error messages or troubleshooting options could have been improved to avoid that. Not everyone has the necessary time or Python skill to dive into the source code, and we'd like to improve SCons for those people as well...
The internal SCons subsystem that handles walking the dependency graph and controls the decision-making about what to rebuild is the Taskmaster. SCons supports a --taskmastertrace option that tells the Taskmaster to print information about the children (dependencies) of the various Nodes on its walk down the graph, which specific dependent Nodes are being evaluated, and in what order.
The --taskmastertrace option takes as an argument the name of a file in which to put the trace output, with - (a single hyphen) indicating that the trace messages should be printed to the standard output:
env = Environment(CPPPATH = ['.']) env.Program('prog.c') |
% scons -Q --taskmastertrace=- prog Taskmaster: Looking for a node to evaluate Taskmaster: Considering node <no_state 0 'prog'> and its children: Taskmaster: <no_state 0 'prog.o'> Taskmaster: adjusting ref count: <pending 1 'prog'> Taskmaster: Considering node <no_state 0 'prog.o'> and its children: Taskmaster: <no_state 0 'prog.c'> Taskmaster: <no_state 0 'inc.h'> Taskmaster: adjusting ref count: <pending 1 'prog.o'> Taskmaster: adjusting ref count: <pending 2 'prog.o'> Taskmaster: Considering node <no_state 0 'prog.c'> and its children: Taskmaster: Evaluating <pending 0 'prog.c'> Taskmaster: Looking for a node to evaluate Taskmaster: Considering node <no_state 0 'inc.h'> and its children: Taskmaster: Evaluating <pending 0 'inc.h'> Taskmaster: Looking for a node to evaluate Taskmaster: Considering node <pending 0 'prog.o'> and its children: Taskmaster: <up_to_date 0 'prog.c'> Taskmaster: <up_to_date 0 'inc.h'> Taskmaster: Evaluating <pending 0 'prog.o'> cc -o prog.o -c -I. prog.c Taskmaster: Looking for a node to evaluate Taskmaster: Considering node <pending 0 'prog'> and its children: Taskmaster: <executed 0 'prog.o'> Taskmaster: Evaluating <pending 0 'prog'> cc -o prog prog.o Taskmaster: Looking for a node to evaluate Taskmaster: No candidate anymore. |
The --taskmastertrace option doesn't provide information about the actual calculations involved in deciding if a file is up-to-date, but it does show all of the dependencies it knows about for each Node, and the order in which those dependencies are evaluated. This can be useful as an alternate way to determine whether or not your SCons configuration, or the implicit dependency scan, has actually identified all the correct dependencies you want it to.
This appendix contains descriptions of all of the construction variables that are potentially available "out of the box" in this version of SCons. Whether or not setting a construction variable in a construction environment will actually have an effect depends on whether any of the Tools and/or Builders that use the variable have been included in the construction environment.
In this appendix, we have
appended the initial $
(dollar sign) to the beginning of each
variable name when it appears in the text,
but left off the dollar sign
in the left-hand column
where the name appears for each entry.
AR
The static library archiver.
ARCHITECTURE
Specifies the system architecture for which the package is being built. The default is the system architecture of the machine on which SCons is running. This is used to fill in the Architecture: field in an Ipkg control file, and as part of the name of a generated RPM file.
ARCOM
The command line used to generate a static library from object files.
ARCOMSTR
The string displayed when an object file
is generated from an assembly-language source file.
If this is not set, then $ARCOM
(the command line) is displayed.
env = Environment(ARCOMSTR = "Archiving $TARGET") |
ARFLAGS
General options passed to the static library archiver.
AS
The assembler.
ASCOM
The command line used to generate an object file from an assembly-language source file.
ASCOMSTR
The string displayed when an object file
is generated from an assembly-language source file.
If this is not set, then $ASCOM
(the command line) is displayed.
env = Environment(ASCOMSTR = "Assembling $TARGET") |
ASFLAGS
General options passed to the assembler.
ASPPCOM
The command line used to assemble an assembly-language
source file into an object file
after first running the file through the C preprocessor.
Any options specified
in the $ASFLAGS
and $CPPFLAGS
construction variables
are included on this command line.
ASPPCOMSTR
The string displayed when an object file
is generated from an assembly-language source file
after first running the file through the C preprocessor.
If this is not set, then $ASPPCOM
(the command line) is displayed.
env = Environment(ASPPCOMSTR = "Assembling $TARGET") |
ASPPFLAGS
General options when an assembling an assembly-language
source file into an object file
after first running the file through the C preprocessor.
The default is to use the value of $ASFLAGS
.
BIBTEX
The bibliography generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
BIBTEXCOM
The command line used to call the bibliography generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
BIBTEXCOMSTR
The string displayed when generating a bibliography
for TeX or LaTeX.
If this is not set, then $BIBTEXCOM
(the command line) is displayed.
env = Environment(BIBTEXCOMSTR = "Generating bibliography $TARGET") |
BIBTEXFLAGS
General options passed to the bibliography generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
BITKEEPER
The BitKeeper executable.
BITKEEPERCOM
The command line for fetching source files using BitKeeper.
BITKEEPERCOMSTR
The string displayed when fetching
a source file using BitKeeper.
If this is not set, then $BITKEEPERCOM
(the command line) is displayed.
BITKEEPERGET
The command ($BITKEEPER
) and subcommand
for fetching source files using BitKeeper.
BITKEEPERGETFLAGS
Options that are passed to the BitKeeper get subcommand.
BUILDERS
A dictionary mapping the names of the builders available through this environment to underlying Builder objects. Builders named Alias, CFile, CXXFile, DVI, Library, Object, PDF, PostScript, and Program are available by default. If you initialize this variable when an Environment is created:
env = Environment(BUILDERS = {'NewBuilder' : foo}) |
the default Builders will no longer be available. To use a new Builder object in addition to the default Builders, add your new Builder object like this:
env = Environment() env.Append(BUILDERS = {'NewBuilder' : foo}) |
or this:
env = Environment() env['BUILDERS]['NewBuilder'] = foo |
CC
The C compiler.
CCCOM
The command line used to compile a C source file to a (static) object
file. Any options specified in the $CFLAGS
, $CCFLAGS
and
$CPPFLAGS
construction variables are included on this command
line.
CCCOMSTR
The string displayed when a C source file
is compiled to a (static) object file.
If this is not set, then $CCCOM
(the command line) is displayed.
env = Environment(CCCOMSTR = "Compiling static object $TARGET") |
CCFLAGS
General options that are passed to the C and C++ compilers.
CCPCHFLAGS
Options added to the compiler command line
to support building with precompiled headers.
The default value expands expands to the appropriate
Microsoft Visual C++ command-line options
when the $PCH
construction variable is set.
CCPDBFLAGS
Options added to the compiler command line
to support storing debugging information in a
Microsoft Visual C++ PDB file.
The default value expands expands to appropriate
Microsoft Visual C++ command-line options
when the $PDB
construction variable is set.
The Visual C++ compiler option that SCons uses by default
to generate PDB information is /Z7
.
This works correctly with parallel (-j
) builds
because it embeds the debug information in the intermediate object files,
as opposed to sharing a single PDB file between multiple object files.
This is also the only way to get debug information
embedded into a static library.
Using the /Zi
instead may yield improved
link-time performance,
although parallel builds will no longer work.
You can generate PDB files with the /Zi
switch by overriding the default $CCPDBFLAGS
variable as follows:
env['CCPDBFLAGS'] = ['${(PDB and "/Zi /Fd%s" % File(PDB)) or ""}'] |
An alternative would be to use the /Zi
to put the debugging information in a separate .pdb
file for each object file by overriding
the $CCPDBFLAGS
variable as follows:
env['CCPDBFLAGS'] = '/Zi /Fd${TARGET}.pdb' |
CCVERSION
The version number of the C compiler. This may or may not be set, depending on the specific C compiler being used.
CFILESUFFIX
The suffix for C source files. This is used by the internal CFile builder when generating C files from Lex (.l) or YACC (.y) input files. The default suffix, of course, is .c (lower case). On case-insensitive systems (like Windows), SCons also treats .C (upper case) files as C files.
CFLAGS
General options that are passed to the C compiler (C only; not C++).
CHANGE_SPECFILE
A hook for modifying the file that controls the packaging build (the .spec for RPM, the control for Ipkg, the .wxs for MSI). If set, the function will be called after the SCons template for the file has been written. XXX
CHANGELOG
The name of a file containing the change log text to be included in the package. This is included as the %changelog section of the RPM .spec file.
_concat
A function used to produce variables like $_CPPINCFLAGS
. It takes
four or five
arguments: a prefix to concatenate onto each element, a list of
elements, a suffix to concatenate onto each element, an environment
for variable interpolation, and an optional function that will be
called to transform the list before concatenation.
env['_CPPINCFLAGS'] = '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs)} $)', |
CONFIGUREDIR
The name of the directory in which Configure context test files are written. The default is .sconf_temp in the top-level directory containing the SConstruct file.
CONFIGURELOG
The name of the Configure context log file. The default is config.log in the top-level directory containing the SConstruct file.
_CPPDEFFLAGS
An automatically-generated construction variable
containing the C preprocessor command-line options
to define values.
The value of $_CPPDEFFLAGS
is created
by appending $CPPDEFPREFIX
and $CPPDEFSUFFIX
to the beginning and end
of each directory in $CPPDEFINES
.
CPPDEFINES
A platform independent specification of C preprocessor definitions.
The definitions will be added to command lines
through the automatically-generated
$_CPPDEFFLAGS
construction variable (see above),
which is constructed according to
the type of value of $CPPDEFINES
:
If $CPPDEFINES
is a string,
the values of the
$CPPDEFPREFIX
and $CPPDEFSUFFIX
construction variables
will be added to the beginning and end.
# Will add -Dxyz to POSIX compiler command lines, # and /Dxyz to Microsoft Visual C++ command lines. env = Environment(CPPDEFINES='xyz') |
If $CPPDEFINES
is a list,
the values of the
$CPPDEFPREFIX
and $CPPDEFSUFFIX
construction variables
will be appended to the beginning and end
of each element in the list.
If any element is a list or tuple,
then the first item is the name being
defined and the second item is its value:
# Will add -DB=2 -DA to POSIX compiler command lines, # and /DB=2 /DA to Microsoft Visual C++ command lines. env = Environment(CPPDEFINES=[('B', 2), 'A']) |
If $CPPDEFINES
is a dictionary,
the values of the
$CPPDEFPREFIX
and $CPPDEFSUFFIX
construction variables
will be appended to the beginning and end
of each item from the dictionary.
The key of each dictionary item
is a name being defined
to the dictionary item's corresponding value;
if the value is
None,
then the name is defined without an explicit value.
Note that the resulting flags are sorted by keyword
to ensure that the order of the options on the
command line is consistent each time
scons
is run.
# Will add -DA -DB=2 to POSIX compiler command lines, # and /DA /DB=2 to Microsoft Visual C++ command lines. env = Environment(CPPDEFINES={'B':2, 'A':None}) |
CPPDEFPREFIX
The prefix used to specify preprocessor definitions
on the C compiler command line.
This will be appended to the beginning of each definition
in the $CPPDEFINES
construction variable
when the $_CPPDEFFLAGS
variable is automatically generated.
CPPDEFSUFFIX
The suffix used to specify preprocessor definitions
on the C compiler command line.
This will be appended to the end of each definition
in the $CPPDEFINES
construction variable
when the $_CPPDEFFLAGS
variable is automatically generated.
CPPFLAGS
User-specified C preprocessor options.
These will be included in any command that uses the C preprocessor,
including not just compilation of C and C++ source files
via the $CCCOM
,
$SHCCCOM
,
$CXXCOM
and
$SHCXXCOM
command lines,
but also the $FORTRANPPCOM
,
$SHFORTRANPPCOM
,
$F77PPCOM
and
$SHF77PPCOM
command lines
used to compile a Fortran source file,
and the $ASPPCOM
command line
used to assemble an assembly language source file,
after first running each file through the C preprocessor.
Note that this variable does
not
contain
-I
(or similar) include search path options
that scons generates automatically from $CPPPATH
.
See $_CPPINCFLAGS
, below,
for the variable that expands to those options.
_CPPINCFLAGS
An automatically-generated construction variable
containing the C preprocessor command-line options
for specifying directories to be searched for include files.
The value of $_CPPINCFLAGS
is created
by appending $INCPREFIX
and $INCSUFFIX
to the beginning and end
of each directory in $CPPPATH
.
CPPPATH
The list of directories that the C preprocessor will search for include directories. The C/C++ implicit dependency scanner will search these directories for include files. Don't explicitly put include directory arguments in CCFLAGS or CXXFLAGS because the result will be non-portable and the directories will not be searched by the dependency scanner. Note: directory names in CPPPATH will be looked-up relative to the SConscript directory when they are used in a command. To force scons to look-up a directory relative to the root of the source tree use #:
env = Environment(CPPPATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(CPPPATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_CPPINCFLAGS
construction variable,
which is constructed by
appending the values of the
$INCPREFIX
and $INCSUFFIX
construction variables
to the beginning and end
of each directory in $CPPPATH
.
Any command lines you define that need
the CPPPATH directory list should
include $_CPPINCFLAGS
:
env = Environment(CCCOM="my_compiler $_CPPINCFLAGS -c -o $TARGET $SOURCE") |
CPPSUFFIXES
The list of suffixes of files that will be scanned for C preprocessor implicit dependencies (#include lines). The default list is:
[".c", ".C", ".cxx", ".cpp", ".c++", ".cc", ".h", ".H", ".hxx", ".hpp", ".hh", ".F", ".fpp", ".FPP", ".m", ".mm", ".S", ".spp", ".SPP"] |
CVS
The CVS executable.
CVSCOFLAGS
Options that are passed to the CVS checkout subcommand.
CVSCOM
The command line used to fetch source files from a CVS repository.
CVSCOMSTR
The string displayed when fetching
a source file from a CVS repository.
If this is not set, then $CVSCOM
(the command line) is displayed.
CVSFLAGS
General options that are passed to CVS. By default, this is set to -d $CVSREPOSITORY to specify from where the files must be fetched.
CVSREPOSITORY
The path to the CVS repository.
This is referenced in the default
$CVSFLAGS
value.
CXX
The C++ compiler.
CXXCOM
The command line used to compile a C++ source file to an object file.
Any options specified in the $CXXFLAGS
and
$CPPFLAGS
construction variables
are included on this command line.
CXXCOMSTR
The string displayed when a C++ source file
is compiled to a (static) object file.
If this is not set, then $CXXCOM
(the command line) is displayed.
env = Environment(CXXCOMSTR = "Compiling static object $TARGET") |
CXXFILESUFFIX
The suffix for C++ source files. This is used by the internal CXXFile builder when generating C++ files from Lex (.ll) or YACC (.yy) input files. The default suffix is .cc. SCons also treats files with the suffixes .cpp, .cxx, .c++, and .C++ as C++ files, and files with .mm suffixes as Objective C++ files. On case-sensitive systems (Linux, UNIX, and other POSIX-alikes), SCons also treats .C (upper case) files as C++ files.
CXXFLAGS
General options that are passed to the C++ compiler.
By default, this includes the value of $CCFLAGS
,
so that setting $CCFLAGS
affects both C and C++ compilation.
If you want to add C++-specific flags,
you must set or override the value of $CXXFLAGS
.
CXXVERSION
The version number of the C++ compiler. This may or may not be set, depending on the specific C++ compiler being used.
DESCRIPTION
A long description of the project being packaged. This is included in the relevant section of the file that controls the packaging build.
DESCRIPTION_lang
A language-specific long description for
the specified lang
.
This is used to populate a
%description -l
section of an RPM
.spec file.
Dir
A function that converts a string into a Dir instance relative to the target being built.
Dirs
A function that converts a list of strings into a list of Dir instances relative to the target being built.
DSUFFIXES
The list of suffixes of files that will be scanned for imported D package files. The default list is:
['.d'] |
DVIPDF
The TeX DVI file to PDF file converter.
DVIPDFCOM
The command line used to convert TeX DVI files into a PDF file.
DVIPDFCOMSTR
The string displayed when a TeX DVI file
is converted into a PDF file.
If this is not set, then $DVIPDFCOM
(the command line) is displayed.
DVIPDFFLAGS
General options passed to the TeX DVI file to PDF file converter.
DVIPS
The TeX DVI file to PostScript converter.
DVIPSFLAGS
General options passed to the TeX DVI file to PostScript converter.
ENV
A dictionary of environment variables
to use when invoking commands. When
$ENV
is used in a command all list
values will be joined using the path separator and any other non-string
values will simply be coerced to a string.
Note that, by default,
scons
does
not
propagate the environment in force when you
execute
scons
to the commands used to build target files.
This is so that builds will be guaranteed
repeatable regardless of the environment
variables set at the time
scons
is invoked.
If you want to propagate your environment variables to the commands executed to build target files, you must do so explicitly:
import os env = Environment(ENV = os.environ) |
Note that you can choose only to propagate
certain environment variables.
A common example is
the system
PATH
environment variable,
so that
scons
uses the same utilities
as the invoking shell (or other process):
import os env = Environment(ENV = {'PATH' : os.environ['PATH']}) |
ESCAPE
A function that will be called to escape shell special characters in command lines. The function should take one argument: the command line string to escape; and should return the escaped command line.
F77
The Fortran 77 compiler.
You should normally set the $FORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $F77
if you need to use a specific compiler
or compiler version for Fortran 77 files.
F77COM
The command line used to compile a Fortran 77 source file to an object file.
You only need to set $F77COM
if you need to use a specific
command line for Fortran 77 files.
You should normally set the $FORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
F77COMSTR
The string displayed when a Fortran 77 source file
is compiled to an object file.
If this is not set, then $F77COM
or $FORTRANCOM
(the command line) is displayed.
F77FILESUFFIXES
The list of file extensions for which the F77 dialect will be used. By default, this is ['.f77']
F77FLAGS
General user-specified options that are passed to the Fortran 77 compiler.
Note that this variable does
not
contain
-I
(or similar) include search path options
that scons generates automatically from $F77PATH
.
See
$_F77INCFLAGS
below,
for the variable that expands to those options.
You only need to set $F77FLAGS
if you need to define specific
user options for Fortran 77 files.
You should normally set the $FORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
_F77INCFLAGS
An automatically-generated construction variable
containing the Fortran 77 compiler command-line options
for specifying directories to be searched for include files.
The value of $_F77INCFLAGS
is created
by appending $INCPREFIX
and $INCSUFFIX
to the beginning and end
of each directory in $F77PATH
.
F77PATH
The list of directories that the Fortran 77 compiler will search for include
directories. The implicit dependency scanner will search these
directories for include files. Don't explicitly put include directory
arguments in $F77FLAGS
because the result will be non-portable
and the directories will not be searched by the dependency scanner. Note:
directory names in $F77PATH
will be looked-up relative to the SConscript
directory when they are used in a command. To force
scons
to look-up a directory relative to the root of the source tree use #:
You only need to set $F77PATH
if you need to define a specific
include path for Fortran 77 files.
You should normally set the $FORTRANPATH
variable,
which specifies the include path
for the default Fortran compiler
for all Fortran versions.
env = Environment(F77PATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(F77PATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_F77INCFLAGS
construction variable,
which is constructed by
appending the values of the
$INCPREFIX
and $INCSUFFIX
construction variables
to the beginning and end
of each directory in $F77PATH
.
Any command lines you define that need
the F77PATH directory list should
include $_F77INCFLAGS
:
env = Environment(F77COM="my_compiler $_F77INCFLAGS -c -o $TARGET $SOURCE") |
F77PPCOM
The command line used to compile a Fortran 77 source file to an object file
after first running the file through the C preprocessor.
Any options specified in the $F77FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $F77PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 77 files.
You should normally set the $FORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
F77PPCOMSTR
The string displayed when a Fortran 77 source file
is compiled to an object file
after first running the file through the C preprocessor.
If this is not set, then $F77PPCOM
or $FORTRANPPCOM
(the command line) is displayed.
F77PPFILESUFFIXES
The list of file extensions for which the compilation + preprocessor pass for F77 dialect will be used. By default, this is empty
F90
The Fortran 90 compiler.
You should normally set the $FORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $F90
if you need to use a specific compiler
or compiler version for Fortran 90 files.
F90COM
The command line used to compile a Fortran 90 source file to an object file.
You only need to set $F90COM
if you need to use a specific
command line for Fortran 90 files.
You should normally set the $FORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
F90COMSTR
The string displayed when a Fortran 90 source file
is compiled to an object file.
If this is not set, then $F90COM
or $FORTRANCOM
(the command line) is displayed.
F90FILESUFFIXES
The list of file extensions for which the F90 dialect will be used. By default, this is ['.f90']
F90FLAGS
General user-specified options that are passed to the Fortran 90 compiler.
Note that this variable does
not
contain
-I
(or similar) include search path options
that scons generates automatically from $F90PATH
.
See
$_F90INCFLAGS
below,
for the variable that expands to those options.
You only need to set $F90FLAGS
if you need to define specific
user options for Fortran 90 files.
You should normally set the $FORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
_F90INCFLAGS
An automatically-generated construction variable
containing the Fortran 90 compiler command-line options
for specifying directories to be searched for include files.
The value of $_F90INCFLAGS
is created
by appending $INCPREFIX
and $INCSUFFIX
to the beginning and end
of each directory in $F90PATH
.
F90PATH
The list of directories that the Fortran 90 compiler will search for include
directories. The implicit dependency scanner will search these
directories for include files. Don't explicitly put include directory
arguments in $F90FLAGS
because the result will be non-portable
and the directories will not be searched by the dependency scanner. Note:
directory names in $F90PATH
will be looked-up relative to the SConscript
directory when they are used in a command. To force
scons
to look-up a directory relative to the root of the source tree use #:
You only need to set $F90PATH
if you need to define a specific
include path for Fortran 90 files.
You should normally set the $FORTRANPATH
variable,
which specifies the include path
for the default Fortran compiler
for all Fortran versions.
env = Environment(F90PATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(F90PATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_F90INCFLAGS
construction variable,
which is constructed by
appending the values of the
$INCPREFIX
and $INCSUFFIX
construction variables
to the beginning and end
of each directory in $F90PATH
.
Any command lines you define that need
the F90PATH directory list should
include $_F90INCFLAGS
:
env = Environment(F90COM="my_compiler $_F90INCFLAGS -c -o $TARGET $SOURCE") |
F90PPCOM
The command line used to compile a Fortran 90 source file to an object file
after first running the file through the C preprocessor.
Any options specified in the $F90FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $F90PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 90 files.
You should normally set the $FORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
F90PPCOMSTR
The string displayed when a Fortran 90 source file
is compiled after first running the file through the C preprocessor.
If this is not set, then $F90PPCOM
or $FORTRANPPCOM
(the command line) is displayed.
F90PPFILESUFFIXES
The list of file extensions for which the compilation + preprocessor pass for F90 dialect will be used. By default, this is empty
F95
The Fortran 95 compiler.
You should normally set the $FORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $F95
if you need to use a specific compiler
or compiler version for Fortran 95 files.
F95COM
The command line used to compile a Fortran 95 source file to an object file.
You only need to set $F95COM
if you need to use a specific
command line for Fortran 95 files.
You should normally set the $FORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
F95COMSTR
The string displayed when a Fortran 95 source file
is compiled to an object file.
If this is not set, then $F95COM
or $FORTRANCOM
(the command line) is displayed.
F95FILESUFFIXES
The list of file extensions for which the F95 dialect will be used. By default, this is ['.f95']
F95FLAGS
General user-specified options that are passed to the Fortran 95 compiler.
Note that this variable does
not
contain
-I
(or similar) include search path options
that scons generates automatically from $F95PATH
.
See
$_F95INCFLAGS
below,
for the variable that expands to those options.
You only need to set $F95FLAGS
if you need to define specific
user options for Fortran 95 files.
You should normally set the $FORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
_F95INCFLAGS
An automatically-generated construction variable
containing the Fortran 95 compiler command-line options
for specifying directories to be searched for include files.
The value of $_F95INCFLAGS
is created
by appending $INCPREFIX
and $INCSUFFIX
to the beginning and end
of each directory in $F95PATH
.
F95PATH
The list of directories that the Fortran 95 compiler will search for include
directories. The implicit dependency scanner will search these
directories for include files. Don't explicitly put include directory
arguments in $F95FLAGS
because the result will be non-portable
and the directories will not be searched by the dependency scanner. Note:
directory names in $F95PATH
will be looked-up relative to the SConscript
directory when they are used in a command. To force
scons
to look-up a directory relative to the root of the source tree use #:
You only need to set $F95PATH
if you need to define a specific
include path for Fortran 95 files.
You should normally set the $FORTRANPATH
variable,
which specifies the include path
for the default Fortran compiler
for all Fortran versions.
env = Environment(F95PATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(F95PATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_F95INCFLAGS
construction variable,
which is constructed by
appending the values of the
$INCPREFIX
and $INCSUFFIX
construction variables
to the beginning and end
of each directory in $F95PATH
.
Any command lines you define that need
the F95PATH directory list should
include $_F95INCFLAGS
:
env = Environment(F95COM="my_compiler $_F95INCFLAGS -c -o $TARGET $SOURCE") |
F95PPCOM
The command line used to compile a Fortran 95 source file to an object file
after first running the file through the C preprocessor.
Any options specified in the $F95FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $F95PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 95 files.
You should normally set the $FORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
F95PPCOMSTR
The string displayed when a Fortran 95 source file
is compiled to an object file
after first running the file through the C preprocessor.
If this is not set, then $F95PPCOM
or $FORTRANPPCOM
(the command line) is displayed.
F95PPFILESUFFIXES
The list of file extensions for which the compilation + preprocessor pass for F95 dialect will be used. By default, this is empty
File
A function that converts a string into a File instance relative to the target being built.
FORTRAN
The default Fortran compiler for all versions of Fortran.
FORTRANCOM
The command line used to compile a Fortran source file to an object file.
By default, any options specified
in the $FORTRANFLAGS
,
$CPPFLAGS
,
$_CPPDEFFLAGS
,
$_FORTRANMODFLAG
, and
$_FORTRANINCFLAGS
construction variables
are included on this command line.
FORTRANCOMSTR
The string displayed when a Fortran source file
is compiled to an object file.
If this is not set, then $FORTRANCOM
(the command line) is displayed.
FORTRANFILESUFFIXES
The list of file extensions for which the FORTRAN dialect will be used. By default, this is ['.f', '.for', '.ftn']
FORTRANFLAGS
General user-specified options that are passed to the Fortran compiler.
Note that this variable does
not
contain
-I
(or similar) include or module search path options
that scons generates automatically from $FORTRANPATH
.
See
$_FORTRANINCFLAGS
and $_FORTRANMODFLAG
,
below,
for the variables that expand those options.
_FORTRANINCFLAGS
An automatically-generated construction variable
containing the Fortran compiler command-line options
for specifying directories to be searched for include
files and module files.
The value of $_FORTRANINCFLAGS
is created
by prepending/appending $INCPREFIX
and $INCSUFFIX
to the beginning and end
of each directory in $FORTRANPATH
.
FORTRANMODDIR
Directory location where the Fortran compiler should place any module files it generates. This variable is empty, by default. Some Fortran compilers will internally append this directory in the search path for module files, as well.
FORTRANMODDIRPREFIX
The prefix used to specify a module directory on the Fortran compiler command
line.
This will be appended to the beginning of the directory
in the $FORTRANMODDIR
construction variables
when the $_FORTRANMODFLAG
variables is automatically generated.
FORTRANMODDIRSUFFIX
The suffix used to specify a module directory on the Fortran compiler command
line.
This will be appended to the beginning of the directory
in the $FORTRANMODDIR
construction variables
when the $_FORTRANMODFLAG
variables is automatically generated.
_FORTRANMODFLAG
An automatically-generated construction variable
containing the Fortran compiler command-line option
for specifying the directory location where the Fortran
compiler should place any module files that happen to get
generated during compilation.
The value of $_FORTRANMODFLAG
is created
by prepending/appending $FORTRANMODDIRPREFIX
and
$FORTRANMODDIRSUFFIX
to the beginning and end of the directory in $FORTRANMODDIR
.
FORTRANMODPREFIX
The module file prefix used by the Fortran compiler. SCons assumes that the Fortran compiler follows the quasi-standard naming convention for module files of module_name.mod. As a result, this variable is left empty, by default. For situations in which the compiler does not necessarily follow the normal convention, the user may use this variable. Its value will be appended to every module file name as scons attempts to resolve dependencies.
FORTRANMODSUFFIX
The module file suffix used by the Fortran compiler. SCons assumes that the Fortran compiler follows the quasi-standard naming convention for module files of module_name.mod. As a result, this variable is set to ".mod", by default. For situations in which the compiler does not necessarily follow the normal convention, the user may use this variable. Its value will be appended to every module file name as scons attempts to resolve dependencies.
FORTRANPATH
The list of directories that the Fortran compiler will search for include files and (for some compilers) module files. The Fortran implicit dependency scanner will search these directories for include files (but not module files since they are autogenerated and, as such, may not actually exist at the time the scan takes place). Don't explicitly put include directory arguments in FORTRANFLAGS because the result will be non-portable and the directories will not be searched by the dependency scanner. Note: directory names in FORTRANPATH will be looked-up relative to the SConscript directory when they are used in a command. To force scons to look-up a directory relative to the root of the source tree use #:
env = Environment(FORTRANPATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(FORTRANPATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_FORTRANINCFLAGS
construction variable,
which is constructed by
appending the values of the
$INCPREFIX
and $INCSUFFIX
construction variables
to the beginning and end
of each directory in $FORTRANPATH
.
Any command lines you define that need
the FORTRANPATH directory list should
include $_FORTRANINCFLAGS
:
env = Environment(FORTRANCOM="my_compiler $_FORTRANINCFLAGS -c -o $TARGET $SOURCE") |
FORTRANPPCOM
The command line used to compile a Fortran source file to an object file
after first running the file through the C preprocessor.
By default, any options specified in the $FORTRANFLAGS
,
$CPPFLAGS
,
$_CPPDEFFLAGS
,
$_FORTRANMODFLAG
, and
$_FORTRANINCFLAGS
construction variables are included on this command line.
FORTRANPPCOMSTR
The string displayed when a Fortran source file
is compiled to an object file
after first running the file throught the C preprocessor.
If this is not set, then $FORTRANPPCOM
(the command line) is displayed.
FORTRANPPFILESUFFIXES
The list of file extensions for which the compilation + preprocessor pass for FORTRAN dialect will be used. By default, this is ['.fpp', '.FPP']
FORTRANSUFFIXES
The list of suffixes of files that will be scanned for Fortran implicit dependencies (INCLUDE lines and USE statements). The default list is:
[".f", ".F", ".for", ".FOR", ".ftn", ".FTN", ".fpp", ".FPP", ".f77", ".F77", ".f90", ".F90", ".f95", ".F95"] |
FRAMEWORKPATH
On Mac OS X with gcc,
a list containing the paths to search for frameworks.
Used by the compiler to find framework-style includes like
#include <Fmwk/Header.h>.
Used by the linker to find user-specified frameworks when linking (see
$FRAMEWORKS
).
For example:
env.AppendUnique(FRAMEWORKPATH='#myframeworkdir') |
will add
... -Fmyframeworkdir |
to the compiler and linker command lines.
_FRAMEWORKPATH
On Mac OS X with gcc, an automatically-generated construction variable
containing the linker command-line options corresponding to
$FRAMEWORKPATH
.
FRAMEWORKPATHPREFIX
On Mac OS X with gcc, the prefix to be used for the FRAMEWORKPATH entries.
(see $FRAMEWORKPATH
).
The default value is
-F
.
FRAMEWORKPREFIX
On Mac OS X with gcc,
the prefix to be used for linking in frameworks
(see $FRAMEWORKS
).
The default value is
-framework
.
_FRAMEWORKS
On Mac OS X with gcc, an automatically-generated construction variable containing the linker command-line options for linking with FRAMEWORKS.
FRAMEWORKS
On Mac OS X with gcc, a list of the framework names to be linked into a program or shared library or bundle. The default value is the empty list. For example:
env.AppendUnique(FRAMEWORKS=Split('System Cocoa SystemConfiguration')) |
FRAMEWORKSFLAGS
On Mac OS X with gcc,
general user-supplied frameworks options to be added at
the end of a command
line building a loadable module.
(This has been largely superceded by
the $FRAMEWORKPATH
, $FRAMEWORKPATHPREFIX
,
$FRAMEWORKPREFIX
and $FRAMEWORKS
variables
described above.)
GS
The Ghostscript program used to convert PostScript to PDF files.
GSCOM
The Ghostscript command line used to convert PostScript to PDF files.
GSCOMSTR
The string displayed when
Ghostscript is used to convert
a PostScript file to a PDF file.
If this is not set, then $GSCOM
(the command line) is displayed.
GSFLAGS
General options passed to the Ghostscript program when converting PostScript to PDF files.
IDLSUFFIXES
The list of suffixes of files that will be scanned for IDL implicit dependencies (#include or import lines). The default list is:
[".idl", ".IDL"] |
IMPLICIT_COMMAND_DEPENDENCIES
Controls whether or not SCons will add implicit dependencies for the commands executed to build targets.
By default, SCons will add
to each target
an implicit dependency on the command
represented by the first argument on any
command line it executes.
The specific file for the dependency is
found by searching the
PATH
variable in the
ENV
environment used to execute the command.
If the construction variable
$IMPLICIT_COMMAND_DEPENDENCIES
is set to a false value
(None,
False,
0,
etc.),
then the implicit dependency will
not be added to the targets
built with that construction environment.
env = Environment(IMPLICIT_COMMAND_DEPENDENCIES = 0) |
INCPREFIX
The prefix used to specify an include directory on the C compiler command
line.
This will be appended to the beginning of each directory
in the $CPPPATH
and $FORTRANPATH
construction variables
when the $_CPPINCFLAGS
and $_FORTRANINCFLAGS
variables are automatically generated.
INCSUFFIX
The suffix used to specify an include directory on the C compiler command
line.
This will be appended to the end of each directory
in the $CPPPATH
and $FORTRANPATH
construction variables
when the $_CPPINCFLAGS
and $_FORTRANINCFLAGS
variables are automatically generated.
INSTALL
A function to be called to install a file into a destination file name. The default function copies the file into the destination (and sets the destination file's mode and permission bits to match the source file's). The function takes the following arguments:
def install(dest, source, env): |
dest
is the path name of the destination file.
source
is the path name of the source file.
env
is the construction environment
(a dictionary of construction values)
in force for this file installation.
INSTALLSTR
The string displayed when a file is installed into a destination file name. The default is:
Install file: "$SOURCE" as "$TARGET" |
INTEL_C_COMPILER_VERSION
Set by the "intelc" Tool to the major version number of the Intel C compiler selected for use.
JAR
The Java archive tool.
JARCHDIR
The directory to which the Java archive tool should change
(using the
-C
option).
JARCOM
The command line used to call the Java archive tool.
JARCOMSTR
The string displayed when the Java archive tool
is called
If this is not set, then $JARCOM
(the command line) is displayed.
env = Environment(JARCOMSTR = "JARchiving $SOURCES into $TARGET") |
JARFLAGS
General options passed to the Java archive tool.
By default this is set to
cf
to create the necessary
jar
file.
JARSUFFIX
The suffix for Java archives: .jar by default.
JAVABOOTCLASSPATH
Specifies the list of directories that
will be added to the
javac command line
via the -bootclasspath
option.
The individual directory names will be
separated by the operating system's path separate character
(: on UNIX/Linux/POSIX,
; on Windows).
JAVAC
The Java compiler.
JAVACCOM
The command line used to compile a directory tree containing
Java source files to
corresponding Java class files.
Any options specified in the $JAVACFLAGS
construction variable
are included on this command line.
JAVACCOMSTR
The string displayed when compiling
a directory tree of Java source files to
corresponding Java class files.
If this is not set, then $JAVACCOM
(the command line) is displayed.
env = Environment(JAVACCOMSTR = "Compiling class files $TARGETS from $SOURCES") |
JAVACFLAGS
General options that are passed to the Java compiler.
JAVACLASSDIR
The directory in which Java class files may be found. This is stripped from the beginning of any Java .class file names supplied to the JavaH builder.
JAVACLASSPATH
Specifies the list of directories that
will be searched for Java
.class file.
The directories in this list will be added to the
javac and javah command lines
via the -classpath
option.
The individual directory names will be
separated by the operating system's path separate character
(: on UNIX/Linux/POSIX,
; on Windows).
Note that this currently just adds the specified
directory via the -classpath
option.
SCons does not currently search the
$JAVACLASSPATH
directories for dependency
.class files.
JAVACLASSSUFFIX
The suffix for Java class files; .class by default.
JAVAH
The Java generator for C header and stub files.
JAVAHCOM
The command line used to generate C header and stub files
from Java classes.
Any options specified in the $JAVAHFLAGS
construction variable
are included on this command line.
JAVAHCOMSTR
The string displayed when C header and stub files
are generated from Java classes.
If this is not set, then $JAVAHCOM
(the command line) is displayed.
env = Environment(JAVAHCOMSTR = "Generating header/stub file(s) $TARGETS from $SOURCES") |
JAVAHFLAGS
General options passed to the C header and stub file generator for Java classes.
JAVASOURCEPATH
Specifies the list of directories that
will be searched for input
.java file.
The directories in this list will be added to the
javac command line
via the -sourcepath
option.
The individual directory names will be
separated by the operating system's path separate character
(: on UNIX/Linux/POSIX,
; on Windows).
Note that this currently just adds the specified
directory via the -sourcepath
option.
SCons does not currently search the
$JAVASOURCEPATH
directories for dependency
.java files.
JAVASUFFIX
The suffix for Java files; .java by default.
JAVAVERSION
Specifies the Java version being used by the Java builder. This is not currently used to select one version of the Java compiler vs. another. Instead, you should set this to specify the version of Java supported by your javac compiler. The default is 1.4.
This is sometimes necessary because
Java 1.5 changed the file names that are created
for nested anonymous inner classes,
which can cause a mismatch with the files
that SCons expects will be generated by the javac compiler.
Setting $JAVAVERSION
to 1.5
(or 1.6, as appropriate)
can make SCons realize that a Java 1.5 or 1.6
build is actually up to date.
LATEX
The LaTeX structured formatter and typesetter.
LATEXCOM
The command line used to call the LaTeX structured formatter and typesetter.
LATEXCOMSTR
The string displayed when calling
the LaTeX structured formatter and typesetter.
If this is not set, then $LATEXCOM
(the command line) is displayed.
env = Environment(LATEXCOMSTR = "Building $TARGET from LaTeX input $SOURCES") |
LATEXFLAGS
General options passed to the LaTeX structured formatter and typesetter.
LATEXRETRIES
The maximum number of times that LaTeX
will be re-run if the
.log
generated by the $LATEXCOM
command
indicates that there are undefined references.
The default is to try to resolve undefined references
by re-running LaTeX up to three times.
LATEXSUFFIXES
The list of suffixes of files that will be scanned for LaTeX implicit dependencies (\include or \import files). The default list is:
[".tex", ".ltx", ".latex"] |
LDMODULE
The linker for building loadable modules.
By default, this is the same as $SHLINK
.
LDMODULECOM
The command line for building loadable modules.
On Mac OS X, this uses the $LDMODULE
,
$LDMODULEFLAGS
and
$FRAMEWORKSFLAGS
variables.
On other systems, this is the same as $SHLINK
.
LDMODULECOMSTR
The string displayed when building loadable modules.
If this is not set, then $LDMODULECOM
(the command line) is displayed.
LDMODULEFLAGS
General user options passed to the linker for building loadable modules.
LDMODULEPREFIX
The prefix used for loadable module file names.
On Mac OS X, this is null;
on other systems, this is
the same as $SHLIBPREFIX
.
LDMODULESUFFIX
The suffix used for loadable module file names. On Mac OS X, this is null; on other systems, this is the same as $SHLIBSUFFIX.
LEX
The lexical analyzer generator.
LEXCOM
The command line used to call the lexical analyzer generator to generate a source file.
LEXCOMSTR
The string displayed when generating a source file
using the lexical analyzer generator.
If this is not set, then $LEXCOM
(the command line) is displayed.
env = Environment(LEXCOMSTR = "Lex'ing $TARGET from $SOURCES") |
LEXFLAGS
General options passed to the lexical analyzer generator.
_LIBDIRFLAGS
An automatically-generated construction variable
containing the linker command-line options
for specifying directories to be searched for library.
The value of $_LIBDIRFLAGS
is created
by appending $LIBDIRPREFIX
and $LIBDIRSUFFIX
to the beginning and end
of each directory in $LIBPATH
.
LIBDIRPREFIX
The prefix used to specify a library directory on the linker command line.
This will be appended to the beginning of each directory
in the $LIBPATH
construction variable
when the $_LIBDIRFLAGS
variable is automatically generated.
LIBDIRSUFFIX
The suffix used to specify a library directory on the linker command line.
This will be appended to the end of each directory
in the $LIBPATH
construction variable
when the $_LIBDIRFLAGS
variable is automatically generated.
_LIBFLAGS
An automatically-generated construction variable
containing the linker command-line options
for specifying libraries to be linked with the resulting target.
The value of $_LIBFLAGS
is created
by appending $LIBLINKPREFIX
and $LIBLINKSUFFIX
to the beginning and end
of each filename in $LIBS
.
LIBLINKPREFIX
The prefix used to specify a library to link on the linker command line.
This will be appended to the beginning of each library
in the $LIBS
construction variable
when the $_LIBFLAGS
variable is automatically generated.
LIBLINKSUFFIX
The suffix used to specify a library to link on the linker command line.
This will be appended to the end of each library
in the $LIBS
construction variable
when the $_LIBFLAGS
variable is automatically generated.
LIBPATH
The list of directories that will be searched for libraries.
The implicit dependency scanner will search these
directories for include files. Don't explicitly put include directory
arguments in $LINKFLAGS
or $SHLINKFLAGS
because the result will be non-portable
and the directories will not be searched by the dependency scanner. Note:
directory names in LIBPATH will be looked-up relative to the SConscript
directory when they are used in a command. To force
scons
to look-up a directory relative to the root of the source tree use #:
env = Environment(LIBPATH='#/libs') |
The directory look-up can also be forced using the Dir() function:
libs = Dir('libs') env = Environment(LIBPATH=libs) |
The directory list will be added to command lines
through the automatically-generated
$_LIBDIRFLAGS
construction variable,
which is constructed by
appending the values of the
$LIBDIRPREFIX
and $LIBDIRSUFFIX
construction variables
to the beginning and end
of each directory in $LIBPATH
.
Any command lines you define that need
the LIBPATH directory list should
include $_LIBDIRFLAGS
:
env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE") |
LIBPREFIX
The prefix used for (static) library file names. A default value is set for each platform (posix, win32, os2, etc.), but the value is overridden by individual tools (ar, mslib, sgiar, sunar, tlib, etc.) to reflect the names of the libraries they create.
LIBPREFIXES
A list of all legal prefixes for library file names.
When searching for library dependencies,
SCons will look for files with these prefixes,
the base library name,
and suffixes in the $LIBSUFFIXES
list.
LIBS
A list of one or more libraries that will be linked with any executable programs created by this environment.
The library list will be added to command lines
through the automatically-generated
$_LIBFLAGS
construction variable,
which is constructed by
appending the values of the
$LIBLINKPREFIX
and $LIBLINKSUFFIX
construction variables
to the beginning and end
of each filename in $LIBS
.
Any command lines you define that need
the LIBS library list should
include $_LIBFLAGS
:
env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE") |
If you add a
File
object to the
$LIBS
list, the name of that file will be added to
$_LIBFLAGS
,
and thus the link line, as is, without
$LIBLINKPREFIX
or
$LIBLINKSUFFIX
.
For example:
env.Append(LIBS=File('/tmp/mylib.so')) |
In all cases, scons will add dependencies from the executable program to all the libraries in this list.
LIBSUFFIX
The suffix used for (static) library file names. A default value is set for each platform (posix, win32, os2, etc.), but the value is overridden by individual tools (ar, mslib, sgiar, sunar, tlib, etc.) to reflect the names of the libraries they create.
LIBSUFFIXES
A list of all legal suffixes for library file names.
When searching for library dependencies,
SCons will look for files with prefixes, in the $LIBPREFIXES
list,
the base library name,
and these suffixes.
LICENSE
The abbreviated name of the license under which this project is released (gpl, lpgl, bsd etc.). See http://www.opensource.org/licenses/alphabetical for a list of license names.
LINK
The linker.
LINKCOM
The command line used to link object files into an executable.
LINKCOMSTR
The string displayed when object files
are linked into an executable.
If this is not set, then $LINKCOM
(the command line) is displayed.
env = Environment(LINKCOMSTR = "Linking $TARGET") |
LINKFLAGS
General user options passed to the linker.
Note that this variable should
not
contain
-l
(or similar) options for linking with the libraries listed in $LIBS
,
nor
-L
(or similar) library search path options
that scons generates automatically from $LIBPATH
.
See
$_LIBFLAGS
above,
for the variable that expands to library-link options,
and
$_LIBDIRFLAGS
above,
for the variable that expands to library search path options.
M4
The M4 macro preprocessor.
M4COM
The command line used to pass files through the M4 macro preprocessor.
M4COMSTR
The string displayed when
a file is passed through the M4 macro preprocessor.
If this is not set, then $M4COM
(the command line) is displayed.
M4FLAGS
General options passed to the M4 macro preprocessor.
MAKEINDEX
The makeindex generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
MAKEINDEXCOM
The command line used to call the makeindex generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
MAKEINDEXCOMSTR
The string displayed when calling the makeindex generator for the
TeX formatter and typesetter
and the LaTeX structured formatter and typesetter.
If this is not set, then $MAKEINDEXCOM
(the command line) is displayed.
MAKEINDEXFLAGS
General options passed to the makeindex generator for the TeX formatter and typesetter and the LaTeX structured formatter and typesetter.
MAXLINELENGTH
The maximum number of characters allowed on an external command line. On Win32 systems, link lines longer than this many characters are linked via a temporary file name.
MIDL
The Microsoft IDL compiler.
MIDLCOM
The command line used to pass files to the Microsoft IDL compiler.
MIDLCOMSTR
The string displayed when
the Microsoft IDL copmiler is called.
If this is not set, then $MIDLCOM
(the command line) is displayed.
MIDLFLAGS
General options passed to the Microsoft IDL compiler.
MSVS
When the Microsoft Visual Studio tools are initialized, they set up this dictionary with the following keys:
VERSION
:
the version of MSVS being used (can be set via
MSVS_VERSION)
VERSIONS
:
the available versions of MSVS installed
VCINSTALLDIR
:
installed directory of Visual C++
VSINSTALLDIR
:
installed directory of Visual Studio
FRAMEWORKDIR
:
installed directory of the .NET framework
FRAMEWORKVERSIONS
:
list of installed versions of the .NET framework, sorted latest to oldest.
FRAMEWORKVERSION
:
latest installed version of the .NET framework
FRAMEWORKSDKDIR
:
installed location of the .NET SDK.
PLATFORMSDKDIR
:
installed location of the Platform SDK.
PLATFORMSDK_MODULES
:
dictionary of installed Platform SDK modules,
where the dictionary keys are keywords for the various modules, and
the values are 2-tuples where the first is the release date, and the
second is the version number.
If a value isn't set, it wasn't available in the registry.
MSVS_IGNORE_IDE_PATHS
Tells the MS Visual Studio tools to use minimal INCLUDE, LIB, and PATH settings, instead of the settings from the IDE.
For Visual Studio, SCons will (by default) automatically determine
where MSVS is installed, and use the LIB, INCLUDE, and PATH variables
set by the IDE. You can override this behavior by setting these
variables after Environment initialization, or by setting
MSVS_IGNORE_IDE_PATHS = 1
in the Environment initialization.
Specifying this will not leave these unset, but will set them to a
minimal set of paths needed to run the tools successfully.
For VS6, the mininimal set is:
INCLUDE:'<VSDir>\VC98\ATL\include;<VSDir>\VC98\MFC\include;<VSDir>\VC98\include' LIB:'<VSDir>\VC98\MFC\lib;<VSDir>\VC98\lib' PATH:'<VSDir>\Common\MSDev98\bin;<VSDir>\VC98\bin' |
For VS7, it is:
INCLUDE:'<VSDir>\Vc7\atlmfc\include;<VSDir>\Vc7\include' LIB:'<VSDir>\Vc7\atlmfc\lib;<VSDir>\Vc7\lib' PATH:'<VSDir>\Common7\Tools\bin;<VSDir>\Common7\Tools;<VSDir>\Vc7\bin' |
Where '<VSDir>' is the installed location of Visual Studio.
MSVS_PROJECT_BASE_PATH
The string placed in a generated Microsoft Visual Studio solution file as the value of the SccProjectFilePathRelativizedFromConnection0 and SccProjectFilePathRelativizedFromConnection1 attributes of the GlobalSection(SourceCodeControl) section. There is no default value.
MSVS_PROJECT_GUID
The string placed in a generated Microsoft Visual Studio project file as the value of the ProjectGUID attribute. The string is also placed in the SolutionUniqueID attribute of the GlobalSection(SourceCodeControl) section of the Microsoft Visual Studio solution file. There is no default value.
MSVS_SCC_AUX_PATH
The path name
placed in a generated Microsoft Visual Studio project file
as the value of the
SccAuxPath
attribute
if the
MSVS_SCC_PROVIDER
construction variable is also set.
There is no default value.
MSVS_SCC_LOCAL_PATH
The path name
placed in a generated Microsoft Visual Studio project file
as the value of the
SccLocalPath
attribute
if the
MSVS_SCC_PROVIDER
construction variable is also set.
The path name is also placed in the
SccLocalPath0
and
SccLocalPath1
attributes of the
GlobalSection(SourceCodeControl)
section of the Microsoft Visual Studio solution file.
There is no default value.
MSVS_SCC_PROJECT_NAME
The project name placed in a generated Microsoft Visual Studio project file as the value of the SccProjectName attribute. There is no default value.
MSVS_SCC_PROVIDER
The string placed in a generated Microsoft Visual Studio project file as the value of the SccProvider attribute. The string is also placed in the SccProvider1 attribute of the GlobalSection(SourceCodeControl) section of the Microsoft Visual Studio solution file. There is no default value.
MSVS_USE_MFC_DIRS
Tells the MS Visual Studio tool(s) to use
the MFC directories in its default paths
for compiling and linking.
The $MSVS_USE_MFC_DIRS
variable has no effect if the
INCLUDE
or
LIB
environment variables are set explictly.
Under Visual Studio version 6,
setting
$MSVS_USE_MFC_DIRS
to a non-zero value
adds the
ATL\include
and
MFC\include
directories to
the default
INCLUDE
external environment variable,
and adds the
MFC\lib
directory to
the default
LIB
external environment variable.
Under Visual Studio version 7,
setting
$MSVS_USE_MFC_DIRS
to a non-zero value
adds the
atlmfc\include
directory to the default
INCLUDE
external environment variable,
and adds the
atlmfc\lib
directory to the default
LIB
external environment variable.
Under Visual Studio version 8,
setting
$MSVS_USE_MFC_DIRS
to a non-zero value will,
by default,
add the
atlmfc\include
directory to the default
INCLUDE
external environment variable,
and the
atlmfc\lib
directory to the default
LIB
external environment variable.
If, however, the
['MSVS']['PLATFORMSDKDIR']
variable is set,
then the
mfc
and the
atl
subdirectories of the
PLATFORMSDKDIR
are added to the default value of the
INCLUDE
external environment variable,
and the default value of the
LIB
external environment variable is left untouched.
MSVS_VERSION
Sets the preferred version of MSVS to use.
SCons will (by default) select the latest version of MSVS
installed on your machine.
So, if you have version 6 and version 7 (MSVS .NET) installed,
it will prefer version 7.
You can override this by
specifying the
MSVS_VERSION
variable in the Environment initialization, setting it to the
appropriate version ('6.0' or '7.0', for example).
If the given version isn't installed, tool initialization will fail.
MSVSBUILDCOM
The build command line placed in a generated Microsoft Visual Studio project file. The default is to have Visual Studio invoke SCons with any specified build targets.
MSVSCLEANCOM
The clean command line placed in a generated Microsoft Visual Studio project file. The default is to have Visual Studio invoke SCons with the -c option to remove any specified targets.
MSVSENCODING
The encoding string placed in a generated Microsoft Visual Studio project file. The default is encoding Windows-1252.
MSVSPROJECTCOM
The action used to generate Microsoft Visual Studio project files.
MSVSPROJECTSUFFIX
The suffix used for Microsoft Visual Studio project (DSP) files. The default value is .vcproj when using Visual Studio version 7.x (.NET) or later version, and .dsp when using earlier versions of Visual Studio.
MSVSREBUILDCOM
The rebuild command line placed in a generated Microsoft Visual Studio project file. The default is to have Visual Studio invoke SCons with any specified rebuild targets.
MSVSSCONS
The SCons used in generated Microsoft Visual Studio project files. The default is the version of SCons being used to generate the project file.
MSVSSCONSCOM
The default SCons command used in generated Microsoft Visual Studio project files.
MSVSSCONSCRIPT
The sconscript file
(that is,
SConstruct
or
SConscript
file)
that will be invoked by Visual Studio
project files
(through the
$MSVSSCONSCOM
variable).
The default is the same sconscript file
that contains the call to
MSVSProject
to build the project file.
MSVSSCONSFLAGS
The SCons flags used in generated Microsoft Visual Studio project files.
MSVSSOLUTIONCOM
The action used to generate Microsoft Visual Studio solution files.
MSVSSOLUTIONSUFFIX
The suffix used for Microsoft Visual Studio solution (DSW) files. The default value is .sln when using Visual Studio version 7.x (.NET), and .dsw when using earlier versions of Visual Studio.
MWCW_VERSION
The version number of the MetroWerks CodeWarrior C compiler to be used.
MWCW_VERSIONS
A list of installed versions of the MetroWerks CodeWarrior C compiler on this system.
NAME
Specfies the name of the project to package.
no_import_lib
When set to non-zero, suppresses creation of a corresponding Windows static import lib by the SharedLibrary builder when used with MinGW, Microsoft Visual Studio or Metrowerks. This also suppresses creation of an export (.exp) file when using Microsoft Visual Studio.
OBJPREFIX
The prefix used for (static) object file names.
OBJSUFFIX
The suffix used for (static) object file names.
P4
The Perforce executable.
P4COM
The command line used to fetch source files from Perforce.
P4COMSTR
The string displayed when
fetching a source file from Perforce.
If this is not set, then $P4COM
(the command line) is displayed.
P4FLAGS
General options that are passed to Perforce.
PACKAGEROOT
Specifies the directory where all files in resulting archive will be placed if applicable. The default value is "$NAME-$VERSION".
PACKAGETYPE
Selects the package type to build. Currently these are available:
* msi - Microsoft Installer * rpm - Redhat Package Manger * ipkg - Itsy Package Management System * tarbz2 - compressed tar * targz - compressed tar * zip - zip file * src_tarbz2 - compressed tar source * src_targz - compressed tar source * src_zip - zip file source
This may be overridden with the "package_type" command line option.
PACKAGEVERSION
The version of the package (not the underlying project). This is currently only used by the rpm packager and should reflect changes in the packaging, not the underlying project code itself.
PCH
The Microsoft Visual C++ precompiled header that will be used when compiling object files. This variable is ignored by tools other than Microsoft Visual C++. When this variable is defined SCons will add options to the compiler command line to cause it to use the precompiled header, and will also set up the dependencies for the PCH file. Example:
env['PCH'] = 'StdAfx.pch' |
PCHCOM
The command line used by the PCH builder to generated a precompiled header.
PCHCOMSTR
The string displayed when generating a precompiled header.
If this is not set, then $PCHCOM
(the command line) is displayed.
PCHPDBFLAGS
A construction variable that, when expanded,
adds the /yD flag to the command line
only if the $PDB
construction variable is set.
PCHSTOP
This variable specifies how much of a source file is precompiled. This variable is ignored by tools other than Microsoft Visual C++, or when the PCH variable is not being used. When this variable is define it must be a string that is the name of the header that is included at the end of the precompiled portion of the source files, or the empty string if the "#pragma hrdstop" construct is being used:
env['PCHSTOP'] = 'StdAfx.h' |
PDB
The Microsoft Visual C++ PDB file that will store debugging information for object files, shared libraries, and programs. This variable is ignored by tools other than Microsoft Visual C++. When this variable is defined SCons will add options to the compiler and linker command line to cause them to generate external debugging information, and will also set up the dependencies for the PDB file. Example:
env['PDB'] = 'hello.pdb' |
The Visual C++ compiler switch that SCons uses by default
to generate PDB information is /Z7
.
This works correctly with parallel (-j
) builds
because it embeds the debug information in the intermediate object files,
as opposed to sharing a single PDB file between multiple object files.
This is also the only way to get debug information
embedded into a static library.
Using the /Zi
instead may yield improved
link-time performance,
although parallel builds will no longer work.
You can generate PDB files with the /Zi
switch by overriding the default $CCPDBFLAGS
variable;
see the entry for that variable for specific examples.
PDFCOM
A deprecated synonym for $DVIPDFCOM
.
PDFLATEX
The pdflatex utility.
PDFLATEXCOM
The command line used to call the pdflatex utility.
PDFLATEXCOMSTR
The string displayed when calling the pdflatex utility.
If this is not set, then $PDFLATEXCOM
(the command line) is displayed.
env = Environment(PDFLATEX;COMSTR = "Building $TARGET from LaTeX input $SOURCES") |
PDFLATEXFLAGS
General options passed to the pdflatex utility.
PDFPREFIX
The prefix used for PDF file names.
PDFSUFFIX
The suffix used for PDF file names.
PDFTEX
The pdftex utility.
PDFTEXCOM
The command line used to call the pdftex utility.
PDFTEXCOMSTR
The string displayed when calling the pdftex utility.
If this is not set, then $PDFTEXCOM
(the command line) is displayed.
env = Environment(PDFTEXCOMSTR = "Building $TARGET from TeX input $SOURCES") |
PDFTEXFLAGS
General options passed to the pdftex utility.
PKGCHK
On Solaris systems,
the package-checking program that will
be used (along with $PKGINFO
)
to look for installed versions of
the Sun PRO C++ compiler.
The default is
/usr/sbin/pgkchk.
PKGINFO
On Solaris systems,
the package information program that will
be used (along with $PKGCHK
)
to look for installed versions of
the Sun PRO C++ compiler.
The default is
pkginfo.
PLATFORM
The name of the platform used to create the Environment. If no platform is specified when the Environment is created, scons autodetects the platform.
env = Environment(tools = []) if env['PLATFORM'] == 'cygwin': Tool('mingw')(env) else: Tool('msvc')(env) |
PRINT_CMD_LINE_FUNC
A Python function used to print the command lines as they are executed
(assuming command printing is not disabled by the
-q
or
-s
options or their equivalents).
The function should take four arguments:
s
,
the command being executed (a string),
target
,
the target being built (file node, list, or string name(s)),
source
,
the source(s) used (file node, list, or string name(s)), and
env
,
the environment being used.
The function must do the printing itself. The default implementation, used if this variable is not set or is None, is:
def print_cmd_line(s, target, source, env): sys.stdout.write(s + "\n") |
Here's an example of a more interesting function:
def print_cmd_line(s, target, source, env): sys.stdout.write("Building %s -> %s...\n" % (' and '.join([str(x) for x in source]), ' and '.join([str(x) for x in target]))) env=Environment(PRINT_CMD_LINE_FUNC=print_cmd_line) env.Program('foo', 'foo.c') |
This just prints "Building targetname
from sourcename
..." instead
of the actual commands.
Such a function could also log the actual commands to a log file,
for example.
PROGPREFIX
The prefix used for executable file names.
PROGSUFFIX
The suffix used for executable file names.
PSCOM
The command line used to convert TeX DVI files into a PostScript file.
PSCOMSTR
The string displayed when a TeX DVI file
is converted into a PostScript file.
If this is not set, then $PSCOM
(the command line) is displayed.
PSPREFIX
The prefix used for PostScript file names.
PSSUFFIX
The prefix used for PostScript file names.
QT_AUTOSCAN
Turn off scanning for mocable files. Use the Moc Builder to explicitely specify files to run moc on.
QT_BINPATH
The path where the qt binaries are installed.
The default value is '$QTDIR
/bin'.
QT_CPPPATH
The path where the qt header files are installed.
The default value is '$QTDIR
/include'.
Note: If you set this variable to None,
the tool won't change the $CPPPATH
construction variable.
QT_DEBUG
Prints lots of debugging information while scanning for moc files.
QT_LIB
Default value is 'qt'. You may want to set this to 'qt-mt'. Note: If you set
this variable to None, the tool won't change the $LIBS
variable.
QT_LIBPATH
The path where the qt libraries are installed.
The default value is '$QTDIR
/lib'.
Note: If you set this variable to None,
the tool won't change the $LIBPATH
construction variable.
QT_MOC
Default value is '$QT_BINPATH
/moc'.
QT_MOCCXXPREFIX
Default value is ''. Prefix for moc output files, when source is a cxx file.
QT_MOCCXXSUFFIX
Default value is '.moc'. Suffix for moc output files, when source is a cxx file.
QT_MOCFROMCXXCOM
Command to generate a moc file from a cpp file.
QT_MOCFROMCXXCOMSTR
The string displayed when generating a moc file from a cpp file.
If this is not set, then $QT_MOCFROMCXXCOM
(the command line) is displayed.
QT_MOCFROMCXXFLAGS
Default value is '-i'. These flags are passed to moc, when moccing a C++ file.
QT_MOCFROMHCOM
Command to generate a moc file from a header.
QT_MOCFROMHCOMSTR
The string displayed when generating a moc file from a cpp file.
If this is not set, then $QT_MOCFROMHCOM
(the command line) is displayed.
QT_MOCFROMHFLAGS
Default value is ''. These flags are passed to moc, when moccing a header file.
QT_MOCHPREFIX
Default value is 'moc_'. Prefix for moc output files, when source is a header.
QT_MOCHSUFFIX
Default value is '$CXXFILESUFFIX
'. Suffix for moc output files, when source is
a header.
QT_UIC
Default value is '$QT_BINPATH
/uic'.
QT_UICCOM
Command to generate header files from .ui files.
QT_UICCOMSTR
The string displayed when generating header files from .ui files.
If this is not set, then $QT_UICCOM
(the command line) is displayed.
QT_UICDECLFLAGS
Default value is ''. These flags are passed to uic, when creating a a h file from a .ui file.
QT_UICDECLPREFIX
Default value is ''. Prefix for uic generated header files.
QT_UICDECLSUFFIX
Default value is '.h'. Suffix for uic generated header files.
QT_UICIMPLFLAGS
Default value is ''. These flags are passed to uic, when creating a cxx file from a .ui file.
QT_UICIMPLPREFIX
Default value is 'uic_'. Prefix for uic generated implementation files.
QT_UICIMPLSUFFIX
Default value is '$CXXFILESUFFIX
'. Suffix for uic generated implementation
files.
QT_UISUFFIX
Default value is '.ui'. Suffix of designer input files.
QTDIR
The qt tool tries to take this from os.environ.
It also initializes all QT_*
construction variables listed below.
(Note that all paths are constructed
with python's os.path.join() method,
but are listed here with the '/' separator
for easier reading.)
In addition, the construction environment
variables $CPPPATH
,
$LIBPATH
and
$LIBS
may be modified
and the variables
PROGEMITTER, SHLIBEMITTER and LIBEMITTER
are modified. Because the build-performance is affected when using this tool,
you have to explicitly specify it at Environment creation:
Environment(tools=['default','qt']) |
The qt tool supports the following operations:
Automatic moc file generation from header files. You do not have to specify moc files explicitly, the tool does it for you. However, there are a few preconditions to do so: Your header file must have the same filebase as your implementation file and must stay in the same directory. It must have one of the suffixes .h, .hpp, .H, .hxx, .hh. You can turn off automatic moc file generation by setting QT_AUTOSCAN to 0. See also the corresponding builder method .B Moc()
Automatic moc file generation from cxx files. As stated in the qt documentation, include the moc file at the end of the cxx file. Note that you have to include the file, which is generated by the transformation ${QT_MOCCXXPREFIX}<basename>${QT_MOCCXXSUFFIX}, by default <basename>.moc. A warning is generated after building the moc file, if you do not include the correct file. If you are using VariantDir, you may need to specify duplicate=1. You can turn off automatic moc file generation by setting QT_AUTOSCAN to 0. See also the corresponding Moc builder method.
Automatic handling of .ui files. The implementation files generated from .ui files are handled much the same as yacc or lex files. Each .ui file given as a source of Program, Library or SharedLibrary will generate three files, the declaration file, the implementation file and a moc file. Because there are also generated headers, you may need to specify duplicate=1 in calls to VariantDir. See also the corresponding Uic builder method.
RANLIB
The archive indexer.
RANLIBCOM
The command line used to index a static library archive.
RANLIBCOMSTR
The string displayed when a static library archive is indexed.
If this is not set, then $RANLIBCOM
(the command line) is displayed.
env = Environment(RANLIBCOMSTR = "Indexing $TARGET") |
RANLIBFLAGS
General options passed to the archive indexer.
RC
The resource compiler used to build a Microsoft Visual C++ resource file.
RCCOM
The command line used to build a Microsoft Visual C++ resource file.
RCCOMSTR
The string displayed when invoking the resource compiler
to build a Microsoft Visual C++ resource file.
If this is not set, then $RCCOM
(the command line) is displayed.
RCFLAGS
The flags passed to the resource compiler by the RES builder.
RCINCFLAGS
An automatically-generated construction variable
containing the command-line options
for specifying directories to be searched
by the resource compiler.
The value of $RCINCFLAGS
is created
by appending $RCINCPREFIX
and $RCINCSUFFIX
to the beginning and end
of each directory in $CPPPATH
.
RCINCPREFIX
The prefix (flag) used to specify an include directory
on the resource compiler command line.
This will be appended to the beginning of each directory
in the $CPPPATH
construction variable
when the $RCINCFLAGS
variable is expanded.
RCINCSUFFIX
The suffix used to specify an include directory
on the resource compiler command line.
This will be appended to the end of each directory
in the $CPPPATH
construction variable
when the $RCINCFLAGS
variable is expanded.
RCS
The RCS executable.
Note that this variable is not actually used
for the command to fetch source files from RCS;
see the
$RCS_CO
construction variable, below.
RCS_CO
The RCS "checkout" executable, used to fetch source files from RCS.
RCS_COCOM
The command line used to fetch (checkout) source files from RCS.
RCS_COCOMSTR
The string displayed when fetching
a source file from RCS.
If this is not set, then $RCS_COCOM
(the command line) is displayed.
RCS_COFLAGS
Options that are passed to the $RCS_CO
command.
RDirs
A function that converts a string into a list of Dir instances by searching the repositories.
REGSVR
The program used on Windows systems to register a newly-built DLL library whenever the SharedLibrary builder is passed a keyword argument of register=1.
REGSVRCOM
The command line used on Windows systems to register a newly-built DLL library whenever the SharedLibrary builder is passed a keyword argument of register=1.
REGSVRCOMSTR
The string displayed when registering a newly-built DLL file.
If this is not set, then $REGSVRCOM
(the command line) is displayed.
REGSVRFLAGS
Flags passed to the DLL registration program
on Windows systems when a newly-built DLL library is registered.
By default,
this includes the /s
that prevents dialog boxes from popping up
and requiring user attention.
RMIC
The Java RMI stub compiler.
RMICCOM
The command line used to compile stub
and skeleton class files
from Java classes that contain RMI implementations.
Any options specified in the $RMICFLAGS
construction variable
are included on this command line.
RMICCOMSTR
The string displayed when compiling
stub and skeleton class files
from Java classes that contain RMI implementations.
If this is not set, then $RMICCOM
(the command line) is displayed.
env = Environment(RMICCOMSTR = "Generating stub/skeleton class files $TARGETS from $SOURCES") |
RMICFLAGS
General options passed to the Java RMI stub compiler.
_RPATH
An automatically-generated construction variable
containing the rpath flags to be used when linking
a program with shared libraries.
The value of $_RPATH
is created
by appending $RPATHPREFIX
and $RPATHSUFFIX
to the beginning and end
of each directory in $RPATH
.
RPATH
A list of paths to search for shared libraries when running programs. Currently only used in the GNU (gnulink), IRIX (sgilink) and Sun (sunlink) linkers. Ignored on platforms and toolchains that don't support it. Note that the paths added to RPATH are not transformed by scons in any way: if you want an absolute path, you must make it absolute yourself.
RPATHPREFIX
The prefix used to specify a directory to be searched for
shared libraries when running programs.
This will be appended to the beginning of each directory
in the $RPATH
construction variable
when the $_RPATH
variable is automatically generated.
RPATHSUFFIX
The suffix used to specify a directory to be searched for
shared libraries when running programs.
This will be appended to the end of each directory
in the $RPATH
construction variable
when the $_RPATH
variable is automatically generated.
RPCGEN
The RPC protocol compiler.
RPCGENCLIENTFLAGS
Options passed to the RPC protocol compiler
when generating client side stubs.
These are in addition to any flags specified in the
$RPCGENFLAGS
construction variable.
RPCGENFLAGS
General options passed to the RPC protocol compiler.
RPCGENHEADERFLAGS
Options passed to the RPC protocol compiler
when generating a header file.
These are in addition to any flags specified in the
$RPCGENFLAGS
construction variable.
RPCGENSERVICEFLAGS
Options passed to the RPC protocol compiler
when generating server side stubs.
These are in addition to any flags specified in the
$RPCGENFLAGS
construction variable.
RPCGENXDRFLAGS
Options passed to the RPC protocol compiler
when generating XDR routines.
These are in addition to any flags specified in the
$RPCGENFLAGS
construction variable.
SCANNERS
A list of the available implicit dependency scanners. New file scanners may be added by appending to this list, although the more flexible approach is to associate scanners with a specific Builder. See the sections "Builder Objects" and "Scanner Objects," below, for more information.
SCCS
The SCCS executable.
SCCSCOM
The command line used to fetch source files from SCCS.
SCCSCOMSTR
The string displayed when fetching
a source file from a CVS repository.
If this is not set, then $SCCSCOM
(the command line) is displayed.
SCCSFLAGS
General options that are passed to SCCS.
SCCSGETFLAGS
Options that are passed specifically to the SCCS "get" subcommand.
This can be set, for example, to
-e
to check out editable files from SCCS.
SCONS_HOME
The (optional) path to the SCons library directory,
initialized from the external environment.
If set, this is used to construct a shorter and more
efficient search path in the
$MSVSSCONS
command line executed
from Microsoft Visual Studio project files.
SHCC
The C compiler used for generating shared-library objects.
SHCCCOM
The command line used to compile a C source file
to a shared-library object file.
Any options specified in the $SHCFLAGS
,
$SHCCFLAGS
and
$CPPFLAGS
construction variables
are included on this command line.
SHCCCOMSTR
The string displayed when a C source file
is compiled to a shared object file.
If this is not set, then $SHCCCOM
(the command line) is displayed.
env = Environment(SHCCCOMSTR = "Compiling shared object $TARGET") |
SHCCFLAGS
Options that are passed to the C and C++ compilers to generate shared-library objects.
SHCFLAGS
Options that are passed to the C compiler (only; not C++) to generate shared-library objects.
SHCXX
The C++ compiler used for generating shared-library objects.
SHCXXCOM
The command line used to compile a C++ source file
to a shared-library object file.
Any options specified in the $SHCXXFLAGS
and
$CPPFLAGS
construction variables
are included on this command line.
SHCXXCOMSTR
The string displayed when a C++ source file
is compiled to a shared object file.
If this is not set, then $SHCXXCOM
(the command line) is displayed.
env = Environment(SHCXXCOMSTR = "Compiling shared object $TARGET") |
SHCXXFLAGS
Options that are passed to the C++ compiler to generate shared-library objects.
SHELL
A string naming the shell program that will be passed to the
$SPAWN
function.
See the
$SPAWN
construction variable for more information.
SHF77
The Fortran 77 compiler used for generating shared-library objects.
You should normally set the $SHFORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $SHF77
if you need to use a specific compiler
or compiler version for Fortran 77 files.
SHF77COM
The command line used to compile a Fortran 77 source file
to a shared-library object file.
You only need to set $SHF77COM
if you need to use a specific
command line for Fortran 77 files.
You should normally set the $SHFORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
SHF77COMSTR
The string displayed when a Fortran 77 source file
is compiled to a shared-library object file.
If this is not set, then $SHF77COM
or $SHFORTRANCOM
(the command line) is displayed.
SHF77FLAGS
Options that are passed to the Fortran 77 compiler
to generated shared-library objects.
You only need to set $SHF77FLAGS
if you need to define specific
user options for Fortran 77 files.
You should normally set the $SHFORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
SHF77PPCOM
The command line used to compile a Fortran 77 source file to a
shared-library object file
after first running the file through the C preprocessor.
Any options specified in the $SHF77FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $SHF77PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 77 files.
You should normally set the $SHFORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
SHF77PPCOMSTR
The string displayed when a Fortran 77 source file
is compiled to a shared-library object file
after first running the file through the C preprocessor.
If this is not set, then $SHF77PPCOM
or $SHFORTRANPPCOM
(the command line) is displayed.
SHF90
The Fortran 90 compiler used for generating shared-library objects.
You should normally set the $SHFORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $SHF90
if you need to use a specific compiler
or compiler version for Fortran 90 files.
SHF90COM
The command line used to compile a Fortran 90 source file
to a shared-library object file.
You only need to set $SHF90COM
if you need to use a specific
command line for Fortran 90 files.
You should normally set the $SHFORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
SHF90COMSTR
The string displayed when a Fortran 90 source file
is compiled to a shared-library object file.
If this is not set, then $SHF90COM
or $SHFORTRANCOM
(the command line) is displayed.
SHF90FLAGS
Options that are passed to the Fortran 90 compiler
to generated shared-library objects.
You only need to set $SHF90FLAGS
if you need to define specific
user options for Fortran 90 files.
You should normally set the $SHFORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
SHF90PPCOM
The command line used to compile a Fortran 90 source file to a
shared-library object file
after first running the file through the C preprocessor.
Any options specified in the $SHF90FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $SHF90PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 90 files.
You should normally set the $SHFORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
SHF90PPCOMSTR
The string displayed when a Fortran 90 source file
is compiled to a shared-library object file
after first running the file through the C preprocessor.
If this is not set, then $SHF90PPCOM
or $SHFORTRANPPCOM
(the command line) is displayed.
SHF95
The Fortran 95 compiler used for generating shared-library objects.
You should normally set the $SHFORTRAN
variable,
which specifies the default Fortran compiler
for all Fortran versions.
You only need to set $SHF95
if you need to use a specific compiler
or compiler version for Fortran 95 files.
SHF95COM
The command line used to compile a Fortran 95 source file
to a shared-library object file.
You only need to set $SHF95COM
if you need to use a specific
command line for Fortran 95 files.
You should normally set the $SHFORTRANCOM
variable,
which specifies the default command line
for all Fortran versions.
SHF95COMSTR
The string displayed when a Fortran 95 source file
is compiled to a shared-library object file.
If this is not set, then $SHF95COM
or $SHFORTRANCOM
(the command line) is displayed.
SHF95FLAGS
Options that are passed to the Fortran 95 compiler
to generated shared-library objects.
You only need to set $SHF95FLAGS
if you need to define specific
user options for Fortran 95 files.
You should normally set the $SHFORTRANFLAGS
variable,
which specifies the user-specified options
passed to the default Fortran compiler
for all Fortran versions.
SHF95PPCOM
The command line used to compile a Fortran 95 source file to a
shared-library object file
after first running the file through the C preprocessor.
Any options specified in the $SHF95FLAGS
and $CPPFLAGS
construction variables
are included on this command line.
You only need to set $SHF95PPCOM
if you need to use a specific
C-preprocessor command line for Fortran 95 files.
You should normally set the $SHFORTRANPPCOM
variable,
which specifies the default C-preprocessor command line
for all Fortran versions.
SHF95PPCOMSTR
The string displayed when a Fortran 95 source file
is compiled to a shared-library object file
after first running the file through the C preprocessor.
If this is not set, then $SHF95PPCOM
or $SHFORTRANPPCOM
(the command line) is displayed.
SHFORTRAN
The default Fortran compiler used for generating shared-library objects.
SHFORTRANCOM
The command line used to compile a Fortran source file to a shared-library object file.
SHFORTRANCOMSTR
The string displayed when a Fortran source file
is compiled to a shared-library object file.
If this is not set, then $SHFORTRANCOM
(the command line) is displayed.
SHFORTRANFLAGS
Options that are passed to the Fortran compiler to generate shared-library objects.
SHFORTRANPPCOM
The command line used to compile a Fortran source file to a
shared-library object file
after first running the file through the C preprocessor.
Any options specified
in the $SHFORTRANFLAGS
and
$CPPFLAGS
construction variables
are included on this command line.
SHFORTRANPPCOMSTR
The string displayed when a Fortran source file
is compiled to a shared-library object file
after first running the file throught the C preprocessor.
If this is not set, then $SHFORTRANPPCOM
(the command line) is displayed.
SHLIBPREFIX
The prefix used for shared library file names.
SHLIBSUFFIX
The suffix used for shared library file names.
SHLINK
The linker for programs that use shared libraries.
SHLINKCOM
The command line used to link programs using shared libaries.
SHLINKCOMSTR
The string displayed when programs using shared libraries are linked.
If this is not set, then $SHLINKCOM
(the command line) is displayed.
env = Environment(SHLINKCOMSTR = "Linking shared $TARGET") |
SHLINKFLAGS
General user options passed to the linker for programs using shared libraries.
Note that this variable should
not
contain
-l
(or similar) options for linking with the libraries listed in $LIBS
,
nor
-L
(or similar) include search path options
that scons generates automatically from $LIBPATH
.
See
$_LIBFLAGS
above,
for the variable that expands to library-link options,
and
$_LIBDIRFLAGS
above,
for the variable that expands to library search path options.
SHOBJPREFIX
The prefix used for shared object file names.
SHOBJSUFFIX
The suffix used for shared object file names.
SOURCE
A reserved variable name that may not be set or used in a construction environment. (See "Variable Substitution," below.)
SOURCE_URL
The URL (web address) of the location from which the project was retrieved. This is used to fill in the Source: field in the controlling information for Ipkg and RPM packages.
SOURCES
A reserved variable name that may not be set or used in a construction environment. (See "Variable Substitution," below.)
SPAWN
A command interpreter function that will be called to execute command line strings. The function must expect the following arguments:
def spawn(shell, escape, cmd, args, env): |
sh
is a string naming the shell program to use.
escape
is a function that can be called to escape shell special characters in
the command line.
cmd
is the path to the command to be executed.
args
is the arguments to the command.
env
is a dictionary of the environment variables
in which the command should be executed.
SUMMARY
A short summary of what the project is about. This is used to fill in the Summary: field in the controlling information for Ipkg and RPM packages, and as the Description: field in MSI packages.
SWIG
The scripting language wrapper and interface generator.
SWIGCFILESUFFIX
The suffix that will be used for intermediate C
source files generated by
the scripting language wrapper and interface generator.
The default value is
_wrap$CFILESUFFIX
.
By default, this value is used whenever the
-c++
option is
not
specified as part of the
$SWIGFLAGS
construction variable.
SWIGCOM
The command line used to call the scripting language wrapper and interface generator.
SWIGCOMSTR
The string displayed when calling
the scripting language wrapper and interface generator.
If this is not set, then $SWIGCOM
(the command line) is displayed.
SWIGCXXFILESUFFIX
The suffix that will be used for intermediate C++
source files generated by
the scripting language wrapper and interface generator.
The default value is
_wrap$CFILESUFFIX
.
By default, this value is used whenever the
-c++
option is specified as part of the
$SWIGFLAGS
construction variable.
SWIGFLAGS
General options passed to
the scripting language wrapper and interface generator.
This is where you should set
-python
,
-perl5
,
-tcl
,
or whatever other options you want to specify to SWIG.
If you set the
-c++
option in this variable,
scons
will, by default,
generate a C++ intermediate source file
with the extension that is specified as the
$CXXFILESUFFIX
variable.
_SWIGINCFLAGS
An automatically-generated construction variable
containing the SWIG command-line options
for specifying directories to be searched for included files.
The value of $_SWIGINCFLAGS
is created
by appending $SWIGINCPREFIX
and $SWIGINCSUFFIX
to the beginning and end
of each directory in $SWIGPATH
.
SWIGINCPREFIX
The prefix used to specify an include directory on the SWIG command line.
This will be appended to the beginning of each directory
in the $SWIGPATH
construction variable
when the $_SWIGINCFLAGS
variable is automatically generated.
SWIGINCSUFFIX
The suffix used to specify an include directory on the SWIG command line.
This will be appended to the end of each directory
in the $SWIGPATH
construction variable
when the $_SWIGINCFLAGS
variable is automatically generated.
SWIGOUTDIR
Specifies the output directory in which the scripting language wrapper and interface generator should place generated language-specific files. This will be used by SCons to identify the files that will be generated by the swig call, and translated into the swig -outdir option on the command line.
SWIGPATH
The list of directories that the scripting language wrapper
and interface generate will search for included files.
The SWIG implicit dependency scanner will search these
directories for include files.
The default is to use the same path
specified as $CPPPATH
.
Don't explicitly put include directory arguments in SWIGFLAGS; the result will be non-portable and the directories will not be searched by the dependency scanner. Note: directory names in SWIGPATH will be looked-up relative to the SConscript directory when they are used in a command. To force scons to look-up a directory relative to the root of the source tree use #:
env = Environment(SWIGPATH='#/include') |
The directory look-up can also be forced using the Dir() function:
include = Dir('include') env = Environment(SWIGPATH=include) |
The directory list will be added to command lines
through the automatically-generated
$_SWIGINCFLAGS
construction variable,
which is constructed by
appending the values of the
$SWIGINCPREFIX
and $SWIGINCSUFFIX
construction variables
to the beginning and end
of each directory in $SWIGPATH
.
Any command lines you define that need
the SWIGPATH directory list should
include $_SWIGINCFLAGS
:
env = Environment(SWIGCOM="my_swig -o $TARGET $_SWIGINCFLAGS $SORUCES") |
TAR
The tar archiver.
TARCOM
The command line used to call the tar archiver.
TARCOMSTR
The string displayed when archiving files
using the tar archiver.
If this is not set, then $TARCOM
(the command line) is displayed.
env = Environment(TARCOMSTR = "Archiving $TARGET") |
TARFLAGS
General options passed to the tar archiver.
TARGET
A reserved variable name that may not be set or used in a construction environment. (See "Variable Substitution," below.)
TARGETS
A reserved variable name that may not be set or used in a construction environment. (See "Variable Substitution," below.)
TARSUFFIX
The suffix used for tar file names.
TEMPFILEPREFIX
The prefix for a temporary file used to execute lines longer than $MAXLINELENGTH. The default is '@'. This may be set for toolchains that use other values, such as '-@' for the diab compiler or '-via' for ARM toolchain.
TEX
The TeX formatter and typesetter.
TEXCOM
The command line used to call the TeX formatter and typesetter.
TEXCOMSTR
The string displayed when calling
the TeX formatter and typesetter.
If this is not set, then $TEXCOM
(the command line) is displayed.
env = Environment(TEXCOMSTR = "Building $TARGET from TeX input $SOURCES") |
TEXFLAGS
General options passed to the TeX formatter and typesetter.
TEXINPUTS
List of directories that the LaTeX programm will search for include directories. The LaTeX implicit dependency scanner will search these directories for \include and \import files.
TOOLS
A list of the names of the Tool specifications that are part of this construction environment.
VENDOR
The person or organization who supply the packaged software. This is used to fill in the Vendor: field in the controlling information for RPM packages, and the Manufacturer: field in the controlling information for MSI packages.
VERSION
The version of the project, specified as a string.
WIN32_INSERT_DEF
A deprecated synonym for $WINDOWS_INSERT_DEF
.
WIN32DEFPREFIX
A deprecated synonym for $WINDOWSDEFPREFIX
.
WIN32DEFSUFFIX
A deprecated synonym for $WINDOWSDEFSUFFIX
.
WIN32EXPPREFIX
A deprecated synonym for $WINDOWSEXPSUFFIX
.
WIN32EXPSUFFIX
A deprecated synonym for $WINDOWSEXPSUFFIX
.
WINDOWS_INSERT_DEF
When this is set to true, a library build of a Windows shared library (.dllfile) will also build a corresponding .def file at the same time, if a .def file is not already listed as a build target. The default is 0 (do not build a .def file).
WINDOWS_INSERT_MANIFEST
When this is set to true, scons will be aware of the .manifest files generated by Microsoft Visua C/C++ 8.
WINDOWSDEFPREFIX
The prefix used for Windows .deffile names.
WINDOWSDEFSUFFIX
The suffix used for Windows .def file names.
WINDOWSEXPPREFIX
The prefix used for Windows .exp file names.
WINDOWSEXPSUFFIX
The suffix used for Windows .exp file names.
WINDOWSPROGMANIFESTPREFIX
The prefix used for executable program .manifest files generated by Microsoft Visual C/C++.
WINDOWSPROGMANIFESTSUFFIX
The suffix used for executable program .manifest files generated by Microsoft Visual C/C++.
WINDOWSSHLIBMANIFESTPREFIX
The prefix used for shared library .manifest files generated by Microsoft Visual C/C++.
WINDOWSSHLIBMANIFESTSUFFIX
The suffix used for shared library .manifest files generated by Microsoft Visual C/C++.
X_IPK_DEPENDS
This is used to fill in the Depends: field in the controlling information for Ipkg packages.
X_IPK_DESCRIPTION
This is used to fill in the Description: field in the controlling information for Ipkg packages. The default value is $SUMMARY\n$DESCRIPTION
X_IPK_MAINTAINER
This is used to fill in the Maintainer: field in the controlling information for Ipkg packages.
X_IPK_PRIORITY
This is used to fill in the Priority: field in the controlling information for Ipkg packages.
X_IPK_SECTION
This is used to fill in the Section: field in the controlling information for Ipkg packages.
X_MSI_LANGUAGE
This is used to fill in the Language: attribute in the controlling information for MSI packages.
X_MSI_LICENSE_TEXT
The text of the software license in RTF format. Carriage return characters will be replaced with the RTF equivalent \\par.
X_MSI_UPGRADE_CODE
TODO
X_RPM_AUTOREQPROV
This is used to fill in the AutoReqProv: field in the RPM .spec file.
X_RPM_BUILD
internal, but overridable
X_RPM_BUILDREQUIRES
This is used to fill in the BuildRequires: field in the RPM .spec file.
X_RPM_BUILDROOT
internal, but overridable
X_RPM_CLEAN
internal, but overridable
X_RPM_CONFLICTS
This is used to fill in the Conflicts: field in the RPM .spec file.
X_RPM_DEFATTR
This value is used as the default attributes for the files in the RPM package. The default value is (-,root,root).
X_RPM_DISTRIBUTION
This is used to fill in the Distribution: field in the RPM .spec file.
X_RPM_EPOCH
This is used to fill in the Epoch: field in the controlling information for RPM packages.
X_RPM_EXCLUDEARCH
This is used to fill in the ExcludeArch: field in the RPM .spec file.
X_RPM_EXLUSIVEARCH
This is used to fill in the ExclusiveArch: field in the RPM .spec file.
X_RPM_GROUP
This is used to fill in the Group: field in the RPM .spec file.
X_RPM_GROUP_lang
This is used to fill in the
Group(lang):
field in the RPM
.spec file.
Note that
lang
is not literal
and should be replaced by
the appropriate language code.
X_RPM_ICON
This is used to fill in the Icon: field in the RPM .spec file.
X_RPM_INSTALL
internal, but overridable
X_RPM_PACKAGER
This is used to fill in the Packager: field in the RPM .spec file.
X_RPM_POSTINSTALL
This is used to fill in the %post: section in the RPM .spec file.
X_RPM_POSTUNINSTALL
This is used to fill in the %postun: section in the RPM .spec file.
X_RPM_PREFIX
This is used to fill in the Prefix: field in the RPM .spec file.
X_RPM_PREINSTALL
This is used to fill in the %pre: section in the RPM .spec file.
X_RPM_PREP
internal, but overridable
X_RPM_PREUNINSTALL
This is used to fill in the %preun: section in the RPM .spec file.
X_RPM_PROVIDES
This is used to fill in the Provides: field in the RPM .spec file.
X_RPM_REQUIRES
This is used to fill in the Requires: field in the RPM .spec file.
X_RPM_SERIAL
This is used to fill in the Serial: field in the RPM .spec file.
X_RPM_URL
This is used to fill in the Url: field in the RPM .spec file.
YACC
The parser generator.
YACCCOM
The command line used to call the parser generator to generate a source file.
YACCCOMSTR
The string displayed when generating a source file
using the parser generator.
If this is not set, then $YACCCOM
(the command line) is displayed.
env = Environment(YACCCOMSTR = "Yacc'ing $TARGET from $SOURCES") |
YACCFLAGS
General options passed to the parser generator.
If $YACCFLAGS
contains a -d
option,
SCons assumes that the call will also create a .h file
(if the yacc source file ends in a .y suffix)
or a .hpp file
(if the yacc source file ends in a .yy suffix)
YACCHFILESUFFIX
The suffix of the C
header file generated by the parser generator
when the
-d
option is used.
Note that setting this variable does not cause
the parser generator to generate a header
file with the specified suffix,
it exists to allow you to specify
what suffix the parser generator will use of its own accord.
The default value is
.h.
YACCHXXFILESUFFIX
The suffix of the C++
header file generated by the parser generator
when the
-d
option is used.
Note that setting this variable does not cause
the parser generator to generate a header
file with the specified suffix,
it exists to allow you to specify
what suffix the parser generator will use of its own accord.
The default value is
.hpp,
except on Mac OS X,
where the default is
${TARGET.suffix}.h.
because the default bison parser generator just
appends .h
to the name of the generated C++ file.
YACCVCGFILESUFFIX
The suffix of the file
containing the VCG grammar automaton definition
when the
--graph=
option is used.
Note that setting this variable does not cause
the parser generator to generate a VCG
file with the specified suffix,
it exists to allow you to specify
what suffix the parser generator will use of its own accord.
The default value is
.vcg.
ZIP
The zip compression and file packaging utility.
ZIPCOM
The command line used to call the zip utility, or the internal Python function used to create a zip archive.
ZIPCOMPRESSION
The
compression
flag
from the Python
zipfile
module used by the internal Python function
to control whether the zip archive
is compressed or not.
The default value is
zipfile.ZIP_DEFLATED,
which creates a compressed zip archive.
This value has no effect when using Python 1.5.2
or if the
zipfile
module is otherwise unavailable.
ZIPCOMSTR
The string displayed when archiving files
using the zip utility.
If this is not set, then $ZIPCOM
(the command line or internal Python function) is displayed.
env = Environment(ZIPCOMSTR = "Zipping $TARGET") |
ZIPFLAGS
General options passed to the zip utility.
ZIPSUFFIX
The suffix used for zip file names.
This appendix contains descriptions of all of the Builders that are potentially available "out of the box" in this version of SCons.
Builds a C source file given a lex (.l)
or yacc (.y) input file.
The suffix specified by the $CFILESUFFIX
construction variable
(.c by default)
is automatically added to the target
if it is not already present.
Example:
# builds foo.c env.CFile(target = 'foo.c', source = 'foo.l') # builds bar.c env.CFile(target = 'bar', source = 'bar.y') |
Builds a C++ source file given a lex (.ll)
or yacc (.yy)
input file.
The suffix specified by the $CXXFILESUFFIX
construction variable
(.cc by default)
is automatically added to the target
if it is not already present.
Example:
# builds foo.cc env.CXXFile(target = 'foo.cc', source = 'foo.ll') # builds bar.cc env.CXXFile(target = 'bar', source = 'bar.yy') |
Builds a .dvi file
from a .tex,
.ltx or .latex input file.
If the source file suffix is .tex,
scons
will examine the contents of the file;
if the string
\documentclass
or
\documentstyle
is found, the file is assumed to be a LaTeX file and
the target is built by invoking the $LATEXCOM
command line;
otherwise, the $TEXCOM
command line is used.
If the file is a LaTeX file,
the
DVI
builder method will also examine the contents
of the
.aux
file and invoke the $BIBTEX
command line
if the string
bibdata
is found,
start $MAKEINDEX
to generate an index if a
.ind
file is found
and will examine the contents
.log
file and re-run the $LATEXCOM
command
if the log file says it is necessary.
The suffix .dvi (hard-coded within TeX itself) is automatically added to the target if it is not already present. Examples:
# builds from aaa.tex env.DVI(target = 'aaa.dvi', source = 'aaa.tex') # builds bbb.dvi env.DVI(target = 'bbb', source = 'bbb.ltx') # builds from ccc.latex env.DVI(target = 'ccc.dvi', source = 'ccc.latex') |
Installs one or more source files or directories in the specified target, which must be a directory. The names of the specified source files or directories remain the same within the destination directory.
env.Install('/usr/local/bin', source = ['foo', 'bar']) |
Installs one or more source files or directories to specific names, allowing changing a file or directory name as part of the installation. It is an error if the target and source arguments list different numbers of files or directories.
env.InstallAs(target = '/usr/local/bin/foo', source = 'foo_debug') env.InstallAs(target = ['../lib/libfoo.a', '../lib/libbar.a'], source = ['libFOO.a', 'libBAR.a']) |
Builds a Java archive (.jar) file from the specified list of sources. Any directories in the source list will be searched for .class files). Any .java files in the source list will be compiled to .class files by calling the Java Builder.
If the $JARCHDIR
value is set, the
jar
command will change to the specified directory using the
-C
option.
If $JARCHDIR
is not set explicitly,
SCons will use the top of any subdirectory tree
in which Java .class
were built by the Java Builder.
If the contents any of the source files begin with the string
Manifest-Version,
the file is assumed to be a manifest
and is passed to the
jar
command with the
m
option set.
env.Jar(target = 'foo.jar', source = 'classes') env.Jar(target = 'bar.jar', source = ['bar1.java', 'bar2.java']) |
Builds one or more Java class files. The sources may be any combination of explicit .java files, or directory trees which will be scanned for .java files.
SCons will parse each source .java file to find the classes (including inner classes) defined within that file, and from that figure out the target .class files that will be created. The class files will be placed underneath the specified target directory.
SCons will also search each Java file
for the Java package name,
which it assumes can be found on a line
beginning with the string
package
in the first column;
the resulting .class files
will be placed in a directory reflecting
the specified package name.
For example,
the file
Foo.java
defining a single public
Foo
class and
containing a package name of
sub.dir
will generate a corresponding
sub/dir/Foo.class
class file.
Examples:
env.Java(target = 'classes', source = 'src') env.Java(target = 'classes', source = ['src1', 'src2']) env.Java(target = 'classes', source = ['File1.java', 'File2.java']) |
Java source files can use the native encoding for the underlying OS. Since SCons compiles in simple ASCII mode by default, the compiler will generate warnings about unmappable characters, which may lead to errors as the file is processed further. In this case, the user must specify the LANG environment variable to tell the compiler what encoding is uesd. For portibility, it's best if the encoding is hard-coded so that the compile will work if it is done on a system with a different encoding.
env = Environment() env['ENV']['LANG'] = 'en_GB.UTF-8' |
Builds C header and source files for implementing Java native methods. The target can be either a directory in which the header files will be written, or a header file name which will contain all of the definitions. The source can be the names of .class files, the names of .java files to be compiled into .class files by calling the Java builder method, or the objects returned from the Java builder method.
If the construction variable
$JAVACLASSDIR
is set, either in the environment
or in the call to the
JavaH
builder method itself,
then the value of the variable
will be stripped from the
beginning of any .class file names.
Examples:
# builds java_native.h classes = env.Java(target = 'classdir', source = 'src') env.JavaH(target = 'java_native.h', source = classes) # builds include/package_foo.h and include/package_bar.h env.JavaH(target = 'include', source = ['package/foo.class', 'package/bar.class']) # builds export/foo.h and export/bar.h env.JavaH(target = 'export', source = ['classes/foo.class', 'classes/bar.class'], JAVACLASSDIR = 'classes') |
A synonym for the StaticLibrary builder method.
On most systems, this is the same as SharedLibrary. On Mac OS X (Darwin) platforms, this creates a loadable module bundle.
Builds an output file from an M4 input file.
This uses a default $M4FLAGS
value of
-E
,
which considers all warnings to be fatal
and stops on the first warning
when using the GNU version of m4.
Example:
env.M4(target = 'foo.c', source = 'foo.c.m4') |
Builds an output file from a moc input file. Moc input files are either
header files or cxx files. This builder is only available after using the
tool 'qt'. See the $QTDIR
variable for more information.
Example:
env.Moc('foo.h') # generates moc_foo.cc env.Moc('foo.cpp') # generates foo.moc |
Builds a Microsoft Visual Studio project file, and by default builds a solution file as well.
This builds a Visual Studio project file, based on the version of
Visual Studio that is configured (either the latest installed version,
or the version specified by
$MSVS_VERSION
in the Environment constructor).
For Visual Studio 6, it will generate a
.dsp
file.
For Visual Studio 7 (.NET) and later versions, it will generate a
.vcproj
file.
By default, this also generates a solution file for the specified project, a .dsw file for Visual Studio 6 or a .sln file for Visual Studio 7 (.NET). This behavior may be disabled by specifying auto_build_solution=0 when you call MSVSProject, in which case you presumably want to build the solution file(s) by calling the MSVSSolution Builder (see below).
The MSVSProject builder
takes several lists of filenames
to be placed into the project file.
These are currently limited to
srcs,
incs,
localincs,
resources,
and
misc.
These are pretty self-explanatory, but it should be noted that these
lists are added to the $SOURCES
construction variable as strings,
NOT as SCons File Nodes. This is because they represent file
names to be added to the project file, not the source files used to
build the project file.
The above filename lists are all optional, although at least one must be specified for the resulting project file to be non-empty.
In addition to the above lists of values, the following values may be specified:
target:
The name of the target
.dsp
or
.vcproj
file.
The correct
suffix for the version of Visual Studio must be used,
but the
$MSVSPROJECTSUFFIX
construction variable
will be defined to the correct value (see example below).
variant: The name of this particular variant. For Visual Studio 7 projects, this can also be a list of variant names. These are typically things like "Debug" or "Release", but really can be anything you want. For Visual Studio 7 projects, they may also specify a target platform separated from the variant name by a | (vertical pipe) character: Debug|Xbox. The default target platform is Win32. Multiple calls to MSVSProject with different variants are allowed; all variants will be added to the project file with their appropriate build targets and sources.
buildtarget: An optional string, node, or list of strings or nodes (one per build variant), to tell the Visual Studio debugger what output target to use in what build variant. The number of buildtarget entries must match the number of variant entries.
runfile: The name of the file that Visual Studio 7 and later will run and debug. This appears as the value of the Output field in the resutling Visual Studio project file. If this is not specified, the default is the same as the specified buildtarget value.
Note that because SCons always executes its build commands
from the directory in which the SConstruct file is located,
if you generate a project file in a different directory
than the SConstruct directory,
users will not be able to double-click
on the file name in compilation error messages
displayed in the Visual Studio console output window.
This can be remedied by adding the
Visual C/C++
.B /FC
compiler option to the $CCFLAGS
variable
so that the compiler will print
the full path name of any
files that cause compilation errors.
Example usage:
barsrcs = ['bar.cpp'], barincs = ['bar.h'], barlocalincs = ['StdAfx.h'] barresources = ['bar.rc','resource.h'] barmisc = ['bar_readme.txt'] dll = env.SharedLibrary(target = 'bar.dll', source = barsrcs) env.MSVSProject(target = 'Bar' + env['MSVSPROJECTSUFFIX'], srcs = barsrcs, incs = barincs, localincs = barlocalincs, resources = barresources, misc = barmisc, buildtarget = dll, variant = 'Release') |
Builds a Microsoft Visual Studio solution file.
This builds a Visual Studio solution file,
based on the version of Visual Studio that is configured
(either the latest installed version,
or the version specified by
$MSVS_VERSION
in the construction environment).
For Visual Studio 6, it will generate a
.dsw
file.
For Visual Studio 7 (.NET), it will
generate a
.sln
file.
The following values must be specified:
target:
The name of the target .dsw or .sln file. The correct
suffix for the version of Visual Studio must be used, but the value
$MSVSSOLUTIONSUFFIX
will be defined to the correct value (see example below).
variant: The name of this particular variant, or a list of variant names (the latter is only supported for MSVS 7 solutions). These are typically things like "Debug" or "Release", but really can be anything you want. For MSVS 7 they may also specify target platform, like this "Debug|Xbox". Default platform is Win32.
projects: A list of project file names, or Project nodes returned by calls to the MSVSProject Builder, to be placed into the solution file. It should be noted that these file names are NOT added to the $SOURCES environment variable in form of files, but rather as strings. This is because they represent file names to be added to the solution file, not the source files used to build the solution file.
(NOTE: Currently only one project is supported per solution.)
Example Usage:
env.MSVSSolution(target = 'Bar' + env['MSVSSOLUTIONSUFFIX'], projects = ['bar' + env['MSVSPROJECTSUFFIX']], variant = 'Release') |
A synonym for the StaticObject builder method.
Builds software distribution packages.
Packages consist of files to install and packaging information.
The former may be specified with the source
parameter and may be left out,
in which case the FindInstalledFiles function will collect
all files that have an Install or InstallAs Builder attached.
If the target
is not specified
it will be deduced from additional information given to this Builder.
The packaging information is specified with the help of construction variables documented below. This information is called a tag to stress that some of them can also be attached to files with the Tag function. The mandatory ones will complain if they were not specified. They vary depending on chosen target packager.
The target packager may be selected with the "PACKAGETYPE" command line
option or with the $PACKAGETYPE
construction variable. Currently
the following packagers available:
* msi - Microsoft Installer * rpm - Redhat Package Manger * ipkg - Itsy Package Management System * tarbz2 - compressed tar * targz - compressed tar * zip - zip file * src_tarbz2 - compressed tar source * src_targz - compressed tar source * src_zip - zip file source
An updated list is always available under the "package_type" option when running "scons --help" on a project that has packaging activated.
env = Environment(tools=['default', 'packaging']) env.Install('/bin/', 'my_program') env.Package( NAME = 'foo', VERSION = '1.2.3', PACKAGEVERSION = 0, PACKAGETYPE = 'rpm', LICENSE = 'gpl', SUMMARY = 'balalalalal', DESCRIPTION = 'this should be really really long', X_RPM_GROUP = 'Application/fu', SOURCE_URL = 'http://foo.org/foo-1.2.3.tar.gz' ) |
Builds a Microsoft Visual C++ precompiled header. Calling this builder method returns a list of two targets: the PCH as the first element, and the object file as the second element. Normally the object file is ignored. This builder method is only provided when Microsoft Visual C++ is being used as the compiler. The PCH builder method is generally used in conjuction with the PCH construction variable to force object files to use the precompiled header:
env['PCH'] = env.PCH('StdAfx.cpp')[0] |
Builds a .pdf file
from a .dvi input file
(or, by extension, a .tex,
.ltx,
or
.latex input file).
The suffix specified by the $PDFSUFFIX
construction variable
(.pdf by default)
is added automatically to the target
if it is not already present. Example:
# builds from aaa.tex env.PDF(target = 'aaa.pdf', source = 'aaa.tex') # builds bbb.pdf from bbb.dvi env.PDF(target = 'bbb', source = 'bbb.dvi') |
Builds a .ps file
from a .dvi input file
(or, by extension, a .tex,
.ltx,
or
.latex input file).
The suffix specified by the $PSSUFFIX
construction variable
(.ps by default)
is added automatically to the target
if it is not already present. Example:
# builds from aaa.tex env.PostScript(target = 'aaa.ps', source = 'aaa.tex') # builds bbb.ps from bbb.dvi env.PostScript(target = 'bbb', source = 'bbb.dvi') |
Builds an executable given one or more object files
or C, C++, D, or Fortran source files.
If any C, C++, D or Fortran source files are specified,
then they will be automatically
compiled to object files using the
Object
builder method;
see that builder method's description for
a list of legal source file suffixes
and how they are interpreted.
The target executable file prefix
(specified by the $PROGPREFIX
construction variable; nothing by default)
and suffix
(specified by the $PROGSUFFIX
construction variable;
by default, .exe on Windows systems,
nothing on POSIX systems)
are automatically added to the target if not already present.
Example:
env.Program(target = 'foo', source = ['foo.o', 'bar.c', 'baz.f']) |
Builds a Microsoft Visual C++ resource file. This builder method is only provided when Microsoft Visual C++ or MinGW is being used as the compiler. The .res (or .o for MinGW) suffix is added to the target name if no other suffix is given. The source file is scanned for implicit dependencies as though it were a C file. Example:
env.RES('resource.rc') |
Builds stub and skeleton class files for remote objects from Java .class files. The target is a directory relative to which the stub and skeleton class files will be written. The source can be the names of .class files, or the objects return from the Java builder method.
If the construction variable
$JAVACLASSDIR
is set, either in the environment
or in the call to the
RMIC
builder method itself,
then the value of the variable
will be stripped from the
beginning of any .class
file names.
classes = env.Java(target = 'classdir', source = 'src') env.RMIC(target = 'outdir1', source = classes) env.RMIC(target = 'outdir2', source = ['package/foo.class', 'package/bar.class']) env.RMIC(target = 'outdir3', source = ['classes/foo.class', 'classes/bar.class'], JAVACLASSDIR = 'classes') |
Generates an RPC client stub (_clnt.c) file from a specified RPC (.x) source file. Because rpcgen only builds output files in the local directory, the command will be executed in the source file's directory by default.
# Builds src/rpcif_clnt.c env.RPCGenClient('src/rpcif.x') |
Generates an RPC header (.h) file from a specified RPC (.x) source file. Because rpcgen only builds output files in the local directory, the command will be executed in the source file's directory by default.
# Builds src/rpcif.h env.RPCGenHeader('src/rpcif.x') |
Generates an RPC server-skeleton (_svc.c) file from a specified RPC (.x) source file. Because rpcgen only builds output files in the local directory, the command will be executed in the source file's directory by default.
# Builds src/rpcif_svc.c env.RPCGenClient('src/rpcif.x') |
Generates an RPC XDR routine (_xdr.c) file from a specified RPC (.x) source file. Because rpcgen only builds output files in the local directory, the command will be executed in the source file's directory by default.
# Builds src/rpcif_xdr.c env.RPCGenClient('src/rpcif.x') |
Builds a shared library
(.so on a POSIX system,
.dll on Windows)
given one or more object files
or C, C++, D or Fortran source files.
If any source files are given,
then they will be automatically
compiled to object files.
The static library prefix and suffix (if any)
are automatically added to the target.
The target library file prefix
(specified by the $SHLIBPREFIX
construction variable;
by default, lib on POSIX systems,
nothing on Windows systems)
and suffix
(specified by the $SHLIBSUFFIX
construction variable;
by default, .dll on Windows systems,
.so on POSIX systems)
are automatically added to the target if not already present.
Example:
env.SharedLibrary(target = 'bar', source = ['bar.c', 'foo.o']) |
On Windows systems, the SharedLibrary builder method will always build an import (.lib) library in addition to the shared (.dll) library, adding a .lib library with the same basename if there is not already a .lib file explicitly listed in the targets.
Any object files listed in the source must have been built for a shared library (that is, using the SharedObject builder method). scons will raise an error if there is any mismatch.
On Windows systems, specifying
register=1
will cause the .dll to be
registered after it is built using REGSVR32.
The command that is run
("regsvr32" by default) is determined by $REGSVR
construction
variable, and the flags passed are determined by $REGSVRFLAGS
. By
default, $REGSVRFLAGS
includes the /s
option,
to prevent dialogs from popping
up and requiring user attention when it is run. If you change
$REGSVRFLAGS
, be sure to include the /s
option.
For example,
env.SharedLibrary(target = 'bar', source = ['bar.cxx', 'foo.obj'], register=1) |
will register bar.dll as a COM object when it is done linking it.
Builds an object file for
inclusion in a shared library.
Source files must have one of the same set of extensions
specified above for the
StaticObject
builder method.
On some platforms building a shared object requires additional
compiler option
(e.g. -fPIC
for gcc)
in addition to those needed to build a
normal (static) object, but on some platforms there is no difference between a
shared object and a normal (static) one. When there is a difference, SCons
will only allow shared objects to be linked into a shared library, and will
use a different suffix for shared objects. On platforms where there is no
difference, SCons will allow both normal (static)
and shared objects to be linked into a
shared library, and will use the same suffix for shared and normal
(static) objects.
The target object file prefix
(specified by the $SHOBJPREFIX
construction variable;
by default, the same as $OBJPREFIX
)
and suffix
(specified by the $SHOBJSUFFIX
construction variable)
are automatically added to the target if not already present.
Examples:
env.SharedObject(target = 'ddd', source = 'ddd.c') env.SharedObject(target = 'eee.o', source = 'eee.cpp') env.SharedObject(target = 'fff.obj', source = 'fff.for') |
Note that the source files will be scanned according to the suffix mappings in the SourceFileScanner object. See the section "Scanner Objects," below, for a more information.
Builds a static library given one or more object files
or C, C++, D or Fortran source files.
If any source files are given,
then they will be automatically
compiled to object files.
The static library prefix and suffix (if any)
are automatically added to the target.
The target library file prefix
(specified by the $LIBPREFIX
construction variable;
by default, lib on POSIX systems,
nothing on Windows systems)
and suffix
(specified by the $LIBSUFFIX
construction variable;
by default, .lib on Windows systems,
.a on POSIX systems)
are automatically added to the target if not already present.
Example:
env.StaticLibrary(target = 'bar', source = ['bar.c', 'foo.o']) |
Any object files listed in the source must have been built for a static library (that is, using the StaticObject builder method). scons will raise an error if there is any mismatch.
Builds a static object file from one or more C, C++, D, or Fortran source files. Source files must have one of the following extensions:
.asm assembly language file .ASM assembly language file .c C file .C Windows: C file POSIX: C++ file .cc C++ file .cpp C++ file .cxx C++ file .cxx C++ file .c++ C++ file .C++ C++ file .d D file .f Fortran file .F Windows: Fortran file POSIX: Fortran file + C pre-processor .for Fortran file .FOR Fortran file .fpp Fortran file + C pre-processor .FPP Fortran file + C pre-processor .m Object C file .mm Object C++ file .s assembly language file .S Windows: assembly language file ARM: CodeSourcery Sourcery Lite .sx assembly language file + C pre-processor POSIX: assembly language file + C pre-processor .spp assembly language file + C pre-processor .SPP assembly language file + C pre-processor |
The target object file prefix
(specified by the $OBJPREFIX
construction variable; nothing by default)
and suffix
(specified by the $OBJSUFFIX
construction variable;
.obj on Windows systems,
.o on POSIX systems)
are automatically added to the target if not already present.
Examples:
env.StaticObject(target = 'aaa', source = 'aaa.c') env.StaticObject(target = 'bbb.o', source = 'bbb.c++') env.StaticObject(target = 'ccc.obj', source = 'ccc.f') |
Note that the source files will be scanned according to the suffix mappings in SourceFileScanner object. See the section "Scanner Objects," below, for a more information.
Builds a tar archive of the specified files and/or directories. Unlike most builder methods, the Tar builder method may be called multiple times for a given target; each additional call adds to the list of entries that will be built into the archive. Any source directories will be scanned for changes to any on-disk files, regardless of whether or not scons knows about them from other Builder or function calls.
env.Tar('src.tar', 'src') # Create the stuff.tar file. env.Tar('stuff', ['subdir1', 'subdir2']) # Also add "another" to the stuff.tar file. env.Tar('stuff', 'another') # Set TARFLAGS to create a gzip-filtered archive. env = Environment(TARFLAGS = '-c -z') env.Tar('foo.tar.gz', 'foo') # Also set the suffix to .tgz. env = Environment(TARFLAGS = '-c -z', TARSUFFIX = '.tgz') env.Tar('foo') |
Builds a Windows type library (.tlb) file from an input IDL file (.idl). In addition, it will build the associated inteface stub and proxy source files, naming them according to the base name of the .idl file. For example,
env.TypeLibrary(source="foo.idl") |
Will create foo.tlb, foo.h, foo_i.c, foo_p.c and foo_data.c files.
Builds a header file, an implementation file and a moc file from an ui file.
and returns the corresponding nodes in the above order.
This builder is only available after using the tool 'qt'. Note: you can
specify .ui files directly as source
files to the Program,
Library and SharedLibrary builders
without using this builder. Using this builder lets you override the standard
naming conventions (be careful: prefixes are always prepended to names of
built files; if you don't want prefixes, you may set them to ``).
See the $QTDIR
variable for more information.
Example:
env.Uic('foo.ui') # -> ['foo.h', 'uic_foo.cc', 'moc_foo.cc'] env.Uic(target = Split('include/foo.h gen/uicfoo.cc gen/mocfoo.cc'), source = 'foo.ui') # -> ['include/foo.h', 'gen/uicfoo.cc', 'gen/mocfoo.cc'] |
Builds a zip archive of the specified files and/or directories. Unlike most builder methods, the Zip builder method may be called multiple times for a given target; each additional call adds to the list of entries that will be built into the archive. Any source directories will be scanned for changes to any on-disk files, regardless of whether or not scons knows about them from other Builder or function calls.
env.Zip('src.zip', 'src') # Create the stuff.zip file. env.Zip('stuff', ['subdir1', 'subdir2']) # Also add "another" to the stuff.tar file. env.Zip('stuff', 'another') |
This appendix contains descriptions of all of the Tools modules that are available "out of the box" in this version of SCons.
Sets construction variables for the 386ASM assembler for the Phar Lap ETS embedded operating system.
Sets: $AS
, $ASCOM
, $ASFLAGS
, $ASPPCOM
, $ASPPFLAGS
.
Uses: $CC
, $CPPFLAGS
, $_CPPDEFFLAGS
, $_CPPINCFLAGS
.
Sets construction variables for the IMB xlc / Visual Age C++ compiler.
Sets: $CXX
, $CXXVERSION
, $SHCXX
, $SHOBJSUFFIX
.
Sets construction variables for the IBM xlc / Visual Age C compiler.
Sets: $CC
, $CCVERSION
, $SHCC
.
Sets construction variables for the IBM Visual Age f77 Fortran compiler.
Sets construction variables for the IBM Visual Age linker.
Sets: $LINKFLAGS
, $SHLIBSUFFIX
, $SHLINKFLAGS
.
Sets construction variables for the Apple linker (similar to the GNU linker).
Sets: $FRAMEWORKPATHPREFIX
, $LDMODULECOM
, $LDMODULEFLAGS
, $LDMODULEPREFIX
, $LDMODULESUFFIX
, $LINKCOM
, $SHLINKCOM
, $SHLINKFLAGS
, $_FRAMEWORKPATH
, $_FRAMEWORKS
.
Uses: $FRAMEWORKSFLAGS
.
Sets construction variables for the ar library archiver.
Sets: $AR
, $ARCOM
, $ARFLAGS
, $LIBPREFIX
, $LIBSUFFIX
, $RANLIB
, $RANLIBCOM
, $RANLIBFLAGS
.
Sets construction variables for the as assembler.
Sets: $AS
, $ASCOM
, $ASFLAGS
, $ASPPCOM
, $ASPPFLAGS
.
Uses: $CC
, $CPPFLAGS
, $_CPPDEFFLAGS
, $_CPPINCFLAGS
.
Sets construction variables for the bcc32 compiler.
Sets: $CC
, $CCCOM
, $CCFLAGS
, $CFILESUFFIX
, $CFLAGS
, $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $INCPREFIX
, $INCSUFFIX
, $SHCC
, $SHCCCOM
, $SHCCFLAGS
, $SHCFLAGS
, $SHOBJSUFFIX
.
Uses: $_CPPDEFFLAGS
, $_CPPINCFLAGS
.
Sets construction variables for the BitKeeper source code control system.
Sets: $BITKEEPER
, $BITKEEPERCOM
, $BITKEEPERGET
, $BITKEEPERGETFLAGS
.
Uses: $BITKEEPERCOMSTR
.
Sets construction variables for generic POSIX C copmilers.
Sets: $CC
, $CCCOM
, $CCFLAGS
, $CFILESUFFIX
, $CFLAGS
, $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $FRAMEWORKPATH
, $FRAMEWORKS
, $INCPREFIX
, $INCSUFFIX
, $SHCC
, $SHCCCOM
, $SHCCFLAGS
, $SHCFLAGS
, $SHOBJSUFFIX
.
Uses: $PLATFORM
.
Sets construction variables for the Compaq Visual Fortran compiler.
Sets: $FORTRAN
, $FORTRANCOM
, $FORTRANMODDIR
, $FORTRANMODDIRPREFIX
, $FORTRANMODDIRSUFFIX
, $FORTRANPPCOM
, $OBJSUFFIX
, $SHFORTRANCOM
, $SHFORTRANPPCOM
.
Uses: $CPPFLAGS
, $FORTRANFLAGS
, $SHFORTRANFLAGS
, $_CPPDEFFLAGS
, $_FORTRANINCFLAGS
, $_FORTRANMODFLAG
.
Sets construction variables for the CVS source code management system.
Sets: $CVS
, $CVSCOFLAGS
, $CVSCOM
, $CVSFLAGS
.
Uses: $CVSCOMSTR
.
Sets construction variables for generic POSIX C++ compilers.
Sets: $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $CXX
, $CXXCOM
, $CXXFILESUFFIX
, $CXXFLAGS
, $INCPREFIX
, $INCSUFFIX
, $OBJSUFFIX
, $SHCXX
, $SHCXXCOM
, $SHCXXFLAGS
, $SHOBJSUFFIX
.
Uses: $CXXCOMSTR
.
Sets variables by calling a default list of Tool modules for the platform on which SCons is running.
Sets construction variables for D language compilers (the Digital Mars D compiler, or GDC).
Attaches the DVI builder to the construction environment.
Sets construction variables for the dvipdf utility.
Sets: $DVIPDF
, $DVIPDFCOM
, $DVIPDFFLAGS
.
Uses: $DVIPDFCOMSTR
.
Sets construction variables for the dvips utility.
Sets: $DVIPS
, $DVIPSFLAGS
, $PSCOM
, $PSPREFIX
, $PSSUFFIX
.
Uses: $PSCOMSTR
.
Set construction variables for generic POSIX Fortran 77 compilers.
Sets: $F77
, $F77COM
, $F77FILESUFFIXES
, $F77FLAGS
, $F77PPCOM
, $F77PPFILESUFFIXES
, $FORTRAN
, $FORTRANCOM
, $FORTRANFLAGS
, $SHF77
, $SHF77COM
, $SHF77FLAGS
, $SHF77PPCOM
, $SHFORTRAN
, $SHFORTRANCOM
, $SHFORTRANFLAGS
, $SHFORTRANPPCOM
, $_F77INCFLAGS
.
Uses: $F77COMSTR
, $F77PPCOMSTR
, $FORTRANCOMSTR
, $FORTRANPPCOMSTR
, $SHF77COMSTR
, $SHF77PPCOMSTR
, $SHFORTRANCOMSTR
, $SHFORTRANPPCOMSTR
.
Set construction variables for generic POSIX Fortran 90 compilers.
Sets: $F90
, $F90COM
, $F90FLAGS
, $F90PPCOM
, $SHF90
, $SHF90COM
, $SHF90FLAGS
, $SHF90PPCOM
, $_F90INCFLAGS
.
Uses: $F90COMSTR
, $F90PPCOMSTR
, $SHF90COMSTR
, $SHF90PPCOMSTR
.
Set construction variables for generic POSIX Fortran 95 compilers.
Sets: $F95
, $F95COM
, $F95FLAGS
, $F95PPCOM
, $SHF95
, $SHF95COM
, $SHF95FLAGS
, $SHF95PPCOM
, $_F95INCFLAGS
.
Uses: $F95COMSTR
, $F95PPCOMSTR
, $SHF95COMSTR
, $SHF95PPCOMSTR
.
Set construction variables for generic POSIX Fortran compilers.
Sets: $FORTRAN
, $FORTRANCOM
, $FORTRANFLAGS
, $SHFORTRAN
, $SHFORTRANCOM
, $SHFORTRANFLAGS
, $SHFORTRANPPCOM
.
Uses: $FORTRANCOMSTR
, $FORTRANPPCOMSTR
, $SHFORTRANCOMSTR
, $SHFORTRANPPCOMSTR
.
Set construction variables for the gXX C++ compiler.
Sets: $CXX
, $CXXVERSION
, $SHCXXFLAGS
, $SHOBJSUFFIX
.
Set construction variables for the g77 Fortran compiler. Calls the f77 Tool module to set variables.
Sets construction variables for the gas assembler. Calls the as module.
Sets: $AS
.
Set construction variables for the gcc C compiler.
Sets: $CC
, $CCVERSION
, $SHCCFLAGS
.
Set construction variables for GNU linker/loader.
Sets: $RPATHPREFIX
, $RPATHSUFFIX
, $SHLINKFLAGS
.
Set construction variables for Ghostscript.
Uses: $GSCOMSTR
.
Set construction variables for the compilers aCC on HP/UX systems.
Set construction variables for the aCC on HP/UX systems. Calls the cXX tool for additional variables.
Sets: $CXX
, $CXXVERSION
, $SHCXXFLAGS
.
Sets construction variables for the linker on HP/UX systems.
Sets: $LINKFLAGS
, $SHLIBSUFFIX
, $SHLINKFLAGS
.
Sets construction variables for the icc compiler on OS/2 systems.
Sets: $CC
, $CCCOM
, $CFILESUFFIX
, $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $CXXCOM
, $CXXFILESUFFIX
, $INCPREFIX
, $INCSUFFIX
.
Uses: $CCFLAGS
, $CFLAGS
, $CPPFLAGS
, $_CPPDEFFLAGS
, $_CPPINCFLAGS
.
Sets construction variables for the Intel C/C++ compiler. Calls the intelc Tool module to set its variables.
Sets construction variables for the Intel Fortran compiler.
Sets: $FORTRAN
, $FORTRANCOM
, $FORTRANPPCOM
, $SHFORTRANCOM
, $SHFORTRANPPCOM
.
Uses: $CPPFLAGS
, $FORTRANFLAGS
, $_CPPDEFFLAGS
, $_FORTRANINCFLAGS
.
Sets construction variables for newer versions of the Intel Fortran compiler for Linux.
Sets: $F77
, $F90
, $F95
, $FORTRAN
, $SHF77
, $SHF77FLAGS
, $SHF90
, $SHF90FLAGS
, $SHF95
, $SHF95FLAGS
, $SHFORTRAN
, $SHFORTRANFLAGS
.
Sets construction variables for the ilink linker on OS/2 systems.
Sets: $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $LINKFLAGS
.
Sets construction variables for the Borland ilink32 linker.
Sets: $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $LINKFLAGS
.
Sets construction variables for file and directory installation.
Sets: $INSTALL
, $INSTALLSTR
.
Sets construction variables for the Intel C/C++ compiler (Linux and Windows, version 7 and later). Calls the gcc or msvc (on Linux and Windows, respectively) to set underlying variables.
Sets: $AR
, $CC
, $CXX
, $INTEL_C_COMPILER_VERSION
, $LINK
.
Sets construction variables for the jar utility.
Sets: $JAR
, $JARCOM
, $JARFLAGS
, $JARSUFFIX
.
Uses: $JARCOMSTR
.
Sets construction variables for the javac compiler.
Sets: $JAVABOOTCLASSPATH
, $JAVAC
, $JAVACCOM
, $JAVACFLAGS
, $JAVACLASSPATH
, $JAVACLASSSUFFIX
, $JAVASOURCEPATH
, $JAVASUFFIX
.
Uses: $JAVACCOMSTR
.
Sets construction variables for the javah tool.
Sets: $JAVACLASSSUFFIX
, $JAVAH
, $JAVAHCOM
, $JAVAHFLAGS
.
Uses: $JAVACLASSPATH
, $JAVAHCOMSTR
.
Sets construction variables for the latex utility.
Sets: $LATEX
, $LATEXCOM
, $LATEXFLAGS
.
Uses: $LATEXCOMSTR
.
Sets construction variables for the lex lexical analyser.
Sets: $LEX
, $LEXCOM
, $LEXFLAGS
.
Uses: $LEXCOMSTR
.
Sets construction variables for generic POSIX linkers.
Sets: $LDMODULE
, $LDMODULECOM
, $LDMODULEFLAGS
, $LDMODULEPREFIX
, $LDMODULESUFFIX
, $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $LINKFLAGS
, $SHLIBSUFFIX
, $SHLINK
, $SHLINKCOM
, $SHLINKFLAGS
.
Uses: $LDMODULECOMSTR
, $LINKCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the LinkLoc linker for the Phar Lap ETS embedded operating system.
Sets: $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $LINKFLAGS
, $SHLINK
, $SHLINKCOM
, $SHLINKFLAGS
.
Uses: $LINKCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the m4 macro processor.
Uses: $M4COMSTR
.
Sets construction variables for the Microsoft assembler.
Sets: $AS
, $ASCOM
, $ASFLAGS
, $ASPPCOM
, $ASPPFLAGS
.
Uses: $ASCOMSTR
, $ASPPCOMSTR
, $CPPFLAGS
, $_CPPDEFFLAGS
, $_CPPINCFLAGS
.
Sets construction variables for the Microsoft IDL compiler.
Sets: $MIDL
, $MIDLCOM
, $MIDLFLAGS
.
Uses: $MIDLCOMSTR
.
Sets construction variables for MinGW (Minimal Gnu on Windows).
Sets: $AS
, $CC
, $CXX
, $LDMODULECOM
, $LIBPREFIX
, $LIBSUFFIX
, $OBJSUFFIX
, $RC
, $RCCOM
, $RCFLAGS
, $RCINCFLAGS
, $RCINCPREFIX
, $RCINCSUFFIX
, $SHCCFLAGS
, $SHCXXFLAGS
, $SHLINKCOM
, $SHLINKFLAGS
, $SHOBJSUFFIX
, $WINDOWSDEFPREFIX
, $WINDOWSDEFSUFFIX
.
Uses: $RCCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the Microsoft mslib library archiver.
Sets: $AR
, $ARCOM
, $ARFLAGS
, $LIBPREFIX
, $LIBSUFFIX
.
Uses: $ARCOMSTR
.
Sets construction variables for the Microsoft linker.
Sets: $LDMODULE
, $LDMODULECOM
, $LDMODULEFLAGS
, $LDMODULEPREFIX
, $LDMODULESUFFIX
, $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $LINKFLAGS
, $REGSVR
, $REGSVRCOM
, $REGSVRFLAGS
, $SHLINK
, $SHLINKCOM
, $SHLINKFLAGS
, $WIN32DEFPREFIX
, $WIN32DEFSUFFIX
, $WIN32EXPPREFIX
, $WIN32EXPSUFFIX
, $WINDOWSDEFPREFIX
, $WINDOWSDEFSUFFIX
, $WINDOWSEXPPREFIX
, $WINDOWSEXPSUFFIX
, $WINDOWSPROGMANIFESTPREFIX
, $WINDOWSPROGMANIFESTSUFFIX
, $WINDOWSSHLIBMANIFESTPREFIX
, $WINDOWSSHLIBMANIFESTSUFFIX
, $WINDOWS_INSERT_DEF
.
Uses: $LDMODULECOMSTR
, $LINKCOMSTR
, $MSVS_IGNORE_IDE_PATHS
, $REGSVRCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the Microsoft Visual C/C++ compiler.
Sets: $BUILDERS
, $CC
, $CCCOM
, $CCFLAGS
, $CCPCHFLAGS
, $CCPDBFLAGS
, $CFILESUFFIX
, $CFLAGS
, $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $CXX
, $CXXCOM
, $CXXFILESUFFIX
, $CXXFLAGS
, $INCPREFIX
, $INCSUFFIX
, $OBJPREFIX
, $OBJSUFFIX
, $PCHCOM
, $PCHPDBFLAGS
, $RC
, $RCCOM
, $RCFLAGS
, $SHCC
, $SHCCCOM
, $SHCCFLAGS
, $SHCFLAGS
, $SHCXX
, $SHCXXCOM
, $SHCXXFLAGS
, $SHOBJPREFIX
, $SHOBJSUFFIX
.
Uses: $CCCOMSTR
, $CXXCOMSTR
, $SHCCCOMSTR
, $SHCXXCOMSTR
.
Sets construction variables for Microsoft Visual Studio.
Sets: $MSVSBUILDCOM
, $MSVSCLEANCOM
, $MSVSENCODING
, $MSVSPROJECTCOM
, $MSVSREBUILDCOM
, $MSVSSCONS
, $MSVSSCONSCOM
, $MSVSSCONSCRIPT
, $MSVSSCONSFLAGS
, $MSVSSOLUTIONCOM
.
Sets construction variables for the Metrowerks CodeWarrior compiler.
Sets: $CC
, $CCCOM
, $CFILESUFFIX
, $CPPDEFPREFIX
, $CPPDEFSUFFIX
, $CXX
, $CXXCOM
, $CXXFILESUFFIX
, $INCPREFIX
, $INCSUFFIX
, $MWCW_VERSION
, $MWCW_VERSIONS
, $SHCC
, $SHCCCOM
, $SHCCFLAGS
, $SHCFLAGS
, $SHCXX
, $SHCXXCOM
, $SHCXXFLAGS
.
Uses: $CCCOMSTR
, $CXXCOMSTR
, $SHCCCOMSTR
, $SHCXXCOMSTR
.
Sets construction variables for the Metrowerks CodeWarrior linker.
Sets: $AR
, $ARCOM
, $LIBDIRPREFIX
, $LIBDIRSUFFIX
, $LIBLINKPREFIX
, $LIBLINKSUFFIX
, $LINK
, $LINKCOM
, $SHLINK
, $SHLINKCOM
, $SHLINKFLAGS
.
Sets construction variables for the nasm Netwide Assembler.
Sets: $AS
, $ASCOM
, $ASFLAGS
, $ASPPCOM
, $ASPPFLAGS
.
Uses: $ASCOMSTR
, $ASPPCOMSTR
.
A framework for building binary and source packages.
Sets construction variables for the Package Builder.
Sets construction variables for the Portable Document Format builder.
Sets: $PDFPREFIX
, $PDFSUFFIX
.
Sets construction variables for the pdflatex utility.
Sets: $LATEXRETRIES
, $PDFLATEX
, $PDFLATEXCOM
, $PDFLATEXFLAGS
.
Uses: $PDFLATEXCOMSTR
.
Sets construction variables for the pdftex utility.
Sets: $LATEXRETRIES
, $PDFLATEX
, $PDFLATEXCOM
, $PDFLATEXFLAGS
, $PDFTEX
, $PDFTEXCOM
, $PDFTEXFLAGS
.
Uses: $PDFLATEXCOMSTR
, $PDFTEXCOMSTR
.
Sets construction variables for interacting with the Perforce source code management system.
Uses: $P4COMSTR
.
Sets construction variables for building Qt applications.
Sets: $QTDIR
, $QT_AUTOSCAN
, $QT_BINPATH
, $QT_CPPPATH
, $QT_LIB
, $QT_LIBPATH
, $QT_MOC
, $QT_MOCCXXPREFIX
, $QT_MOCCXXSUFFIX
, $QT_MOCFROMCXXCOM
, $QT_MOCFROMCXXFLAGS
, $QT_MOCFROMHCOM
, $QT_MOCFROMHFLAGS
, $QT_MOCHPREFIX
, $QT_MOCHSUFFIX
, $QT_UIC
, $QT_UICCOM
, $QT_UICDECLFLAGS
, $QT_UICDECLPREFIX
, $QT_UICDECLSUFFIX
, $QT_UICIMPLFLAGS
, $QT_UICIMPLPREFIX
, $QT_UICIMPLSUFFIX
, $QT_UISUFFIX
.
Sets construction variables for the interaction with the Revision Control System.
Sets: $RCS
, $RCS_CO
, $RCS_COCOM
, $RCS_COFLAGS
.
Uses: $RCS_COCOMSTR
.
Sets construction variables for the rmic utility.
Sets: $JAVACLASSSUFFIX
, $RMIC
, $RMICCOM
, $RMICFLAGS
.
Uses: $RMICCOMSTR
.
Sets construction variables for building with RPCGEN.
Sets: $RPCGEN
, $RPCGENCLIENTFLAGS
, $RPCGENFLAGS
, $RPCGENHEADERFLAGS
, $RPCGENSERVICEFLAGS
, $RPCGENXDRFLAGS
.
Sets construction variables for interacting with the Source Code Control System.
Sets: $SCCS
, $SCCSCOM
, $SCCSFLAGS
, $SCCSGETFLAGS
.
Uses: $SCCSCOMSTR
.
Sets construction variables for the SGI library archiver.
Sets: $AR
, $ARCOMSTR
, $ARFLAGS
, $LIBPREFIX
, $LIBSUFFIX
, $SHLINK
, $SHLINKFLAGS
.
Uses: $ARCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the SGI C++ compiler.
Sets: $CXX
, $CXXFLAGS
, $SHCXX
, $SHOBJSUFFIX
.
Sets construction variables for the SGI C compiler.
Sets: $CXX
, $SHOBJSUFFIX
.
Sets construction variables for the SGI linker.
Sets: $LINK
, $RPATHPREFIX
, $RPATHSUFFIX
, $SHLINKFLAGS
.
Sets construction variables for the Sun library archiver.
Sets: $AR
, $ARCOM
, $ARFLAGS
, $LIBPREFIX
, $LIBSUFFIX
, $SHLINK
, $SHLINKCOM
, $SHLINKFLAGS
.
Uses: $ARCOMSTR
, $SHLINKCOMSTR
.
Sets construction variables for the Sun C++ compiler.
Sets: $CXX
, $CXXVERSION
, $SHCXX
, $SHCXXFLAGS
, $SHOBJPREFIX
, $SHOBJSUFFIX
.
Sets construction variables for the Sun C compiler.
Sets: $CXX
, $SHCCFLAGS
, $SHOBJPREFIX
, $SHOBJSUFFIX
.
Sets construction variables for the Sun linker.
Sets: $RPATHPREFIX
, $RPATHSUFFIX
, $SHLINKFLAGS
.
Sets construction variables for the SWIG interface generator.
Sets: $SWIG
, $SWIGCFILESUFFIX
, $SWIGCOM
, $SWIGCXXFILESUFFIX
, $SWIGFLAGS
, $SWIGINCPREFIX
, $SWIGINCSUFFIX
, $SWIGPATH
, $_SWIGINCFLAGS
.
Uses: $SWIGCOMSTR
.
Sets construction variables for the tar archiver.
Sets: $TAR
, $TARCOM
, $TARFLAGS
, $TARSUFFIX
.
Uses: $TARCOMSTR
.
Sets construction variables for the TeX formatter and typesetter.
Sets: $BIBTEX
, $BIBTEXCOM
, $BIBTEXFLAGS
, $LATEX
, $LATEXCOM
, $LATEXFLAGS
, $MAKEINDEX
, $MAKEINDEXCOM
, $MAKEINDEXFLAGS
, $TEX
, $TEXCOM
, $TEXFLAGS
.
Uses: $BIBTEXCOMSTR
, $LATEXCOMSTR
, $MAKEINDEXCOMSTR
, $TEXCOMSTR
.
Sets construction variables for the Borlan tib library archiver.
Sets: $AR
, $ARCOM
, $ARFLAGS
, $LIBPREFIX
, $LIBSUFFIX
.
Uses: $ARCOMSTR
.
Sets construction variables for the yacc parse generator.
Sets: $YACC
, $YACCCOM
, $YACCFLAGS
, $YACCHFILESUFFIX
, $YACCHXXFILESUFFIX
, $YACCVCGFILESUFFIX
.
Uses: $YACCCOMSTR
.
Sets construction variables for the zip archiver.
Sets: $ZIP
, $ZIPCOM
, $ZIPCOMPRESSION
, $ZIPFLAGS
, $ZIPSUFFIX
.
Uses: $ZIPCOMSTR
.
There is a common set of simple tasks that many build configurations rely on as they become more complex. Most build tools have special purpose constructs for performing these tasks, but since SConscript files are Python scripts, you can use more flexible built-in Python services to perform these tasks. This appendix lists a number of these tasks and how to implement them in Python.
Example 2. Filename extension substitution
import os.path filename = os.path.splitext(filename)[0]+extension |
Example 3. Appending a path prefix to a list of filenames
import os.path filenames = [os.path.join(prefix, x) for x in filenames] |
or in Python 1.5.2:
import os.path new_filenames = [] for x in filenames: new_filenames.append(os.path.join(prefix, x)) |
Example 4. Substituting a path prefix with another one
if filename.find(old_prefix) == 0: filename = filename.replace(old_prefix, new_prefix) |
or in Python 1.5.2:
import string if string.find(filename, old_prefix) == 0: filename = string.replace(filename, old_prefix, new_prefix) |
Example 5. Filtering a filename list to exclude/retain only a specific set of extensions
import os.path filenames = [x for x in filenames if os.path.splitext(x)[1] in extensions] |
or in Python 1.5.2:
import os.path new_filenames = [] for x in filenames: if os.path.splitext(x)[1] in extensions: new_filenames.append(x) |
[1] | In programming parlance, the SConstruct file is declarative, meaning you tell SCons what you want done and let it figure out the order in which to do it, rather than strictly imperative, where you specify explicitly the order in which to do things. |
[2] | This easily-overlooked distinction between how SCons decides if the target itself must be rebuilt and how the target is then used to decide if a different target must be rebuilt is one of the confusing things that has led to the TargetSignatures and SourceSignatures functions being replaced by the simpler Decider function. |
[3] |
The AddOption function is,
in fact, implemented using a subclass
of the |
[4] | Unfortunately, in the early days of SCons design, we used the name Copy for the function that returns a copy of the environment, otherwise that would be the logical choice for a Builder that copies a file or directory tree to a target location. |
[5] | Actually, the MD5 signature is used as the name of the file in the shared cache directory in which the contents are stored. |