GNUstep Base

Authors

Richard Frith-Macdonald (rfm@gnu.org)

Version: $Revision$

Date: $Date$

Copyright: (C) 2005 Free Software Foundation, Inc.

Base

The GNUstep Base library is a free software package implementing the API of the OpenStep Foundation Kit (tm), including later additions. This documentation package describes the core of the Base library, for documentation on additional classes, see the BaseAdditions documentation package.

Read the Release Notes for the current release.

Compatibility

GNUstep is generally compatible with the OpenStep specification and with recent developments of the MacOS (cocoa) API. Where MacOS deviates from the OpenStep API, GNUstep generally attempts to support both versions. In some cases the newer MacOS APIs are incompatible with OpenStep, and GNUstep usually supports the richer version. See the OpenStep Compliance section for more information on OpenStep Compliance.

In order to deal with compatibility issues, GNUstep uses two mechanisms - it provides conditionally compiled sections of the library header files, so that software can be built that will conform strictly to a particular API, and it provides user default settings to control the behavior of the library at runtime.

Conditional compilation

Adding an option to a makefile to define one of the following preprocessor constants will modify the API visible to software being compiled -

GS_GNUSTEP_V
Specifies the software version of the header being included.
Features in that header which are declared as having been introduced at or before the specified version, and not being removed until or after the specified version are available.
The version consists of five or six digits ... a major number (0-99) followed by a minor number (00-99) and a subminor number (00-99).
Features in the header file are marked as belonging to different version ranges using the GS_API_VERSION macro.
NB. This is the native versioning of the library being used via the header file. You can use this mechanism in your own libraries and frameworks.
GS_OPENSTEP_V
Used only for the software version in sequence of OpenStep specification and the NeXT/Apple implementation of that specification and its extensions.
Features in the header being included which are declared as having been introduced at or before the specified version, and not being removed until or after the specified version are available.
The version consists of five or six digits ... a major number (1-99) followed by a minor number (00-99) and a subminor number (00-99).
A major number of 1 indicates the OpenStep specification ... available as the GS_API_OSSPEC preprocessor constant.
A major number of 4 indicates the OPENSTEP implementation ... available as the GS_API_OPENSTEP preprocessor constant.
A major number of 10 indicates the MacOS-X implementation ... available as the GS_API_MACOSX preprocessor constant.
Features in the header file are marked as belonging to different version ranges using the GS_API_VERSION macro.
For MacOS-X compatibility, if this constant is not defined and MAC_OS_X_VERSION_MAX_ALLOWED is defined, then GS_OPENSTEP_V is defined to be MAC_OS_X_VERSION_MAX_ALLOWED.
Similarly, for MacOS-X we define MAC_OS_X_VERSION_10_2, MAC_OS_X_VERSION_10_3 etc as the appropriate numeric version numbers.

NB These preprocessor constants are used in developer code (ie the code that users of GNUstep write) rather than by the GNUstep software itself. They permit a developer to ensure that he/she does not write code which depends upon API not present on other implementations (in practice, MacOS-X or some old OPENSTEP systems).
The actual GNUstep libraries are always built with the full GNUstep API in place, so that the feature set is as consistent as possible.

The presence of these macros is also used by autogsdoc to generate information about which version of the API a particular feature belongs to.

User defaults

GNU-Debug

An array of strings that lists debug levels to be used within the program. These debug levels are merged with any which were set on the command line or added programmatically to the set given by the [NSProcessInfo-debugSet] method.

GSLogSyslog

Setting the user default GSLogSyslog to YES will cause log/debug output to be sent to the syslog facility (on systems which support it), rather than to the standard error stream. This is useful in environments where stderr has been re-used strangely for some reason.
On mswindows, where syslog does not exist, this flag instead controls whether log/debug output is sent to the windows event log.

GSLogThread

Setting the user default GSLogThread to YES will cause NSLog and debug output to include the current thread in the logged message.
This is useful for debugging multi-threaded applications.

GSMacOSXCompatible

Setting the user default GSMacOSXCompatible to YES will cause MacOS compatible behavior to be the default at runtime. This default may however be overridden to provide more fine grained control of system behavior.

GSOldStyleGeometry

Specifies whether the functions for producing strings describing geometric structures (NSStringFromPoint(), NSStringFromSize(), and NSStringFromRect()) should produce strings conforming to the OpenStep specification or to MacOS-X behavior. The functions for parsing those strings should cope with both cases anyway.

GSSOCKS

May be used to specify a default SOCKS5 server (and optionally a port separated from the server by a colon) to which tcp/ip connections made using the NSFileHandle extension methods should be directed.
This default overrides the SOCKS5_SERVER and SOCKS_SERVER environment variables.

Local Time Zone

Used to specify the name of the timezone to be used by the NSTimeZone class.

NSWriteOldStylePropertyLists

Specifies whether text property-list output should be in the default MacOS-X format (XML), or in the more human readable (but less powerful) original OpenStep format.

Reading of property lists is supported in either format, but only if GNUstep is built with the libxml library (which is needed to handle XML parsing).

NB. MacOS-X generates illegal XML for some strings - those which contain characters not legal in XML. GNUstep always generates legal XML, at the cost of a certain degree of compatibility. GNUstep XML property lists use a backslash to escape illegal characters, and consequently any string containing either a backslash or an illegal character will be written differently to the same string on MacOS-X.

NSLanguages

An array of strings that lists the users preferred languages, in order or preference. If not found the default is just English.

Environment variables

There are some environment variables used by GNUstep base, where there would be problems obtaining data from the defaults system.

CRASH_ON_ABORT

The default exception handler will either cause the program to simply terminate, or to crash - leaving a core dump. The standard behavior is to leave a core dump if the library was built for debugging, and to simply exit if it was not.

The CRASH_ON_ABORT environment variable can be used to override this behavior. If this is defined to NO, FALSE, or 0 then the program will simply exit when an exception occurs. Any other value of the variable will cause the program to generate a core dump.

CRASH_ON_ZOMBIE

When the a message is sent to a zombie object (see the NSZombieEnabled environment variable) the base library allows you to specify whether the program should continue after logging the message, or have the program abort.
By default, the program will attempt to continue.

The CRASH_ON_ZOMBIE variable can be used to override this behavior. If this is defined to YES, TRUE, or 1 then the program will log the message sent to the zombie and then abort, producing a core dump on systems where that is possible.

GNUSTEP_SHOULD_CLEAN_UP

When this is set to YES, the GNUstep extension method +setShouldCleanUp: is called when the NSObject class is initialised, this turns on recording of some intentionally leaked memory (data structures intended to persist for the whole life of the process), and activates cleanup of that memory on process exit so that external tools such as valgrind will not report the memory as possibly lost.

Use of this facility is a work in progress ... many classes do not yet clean up after themselves when this is enabled.

GNUSTEP_STACK_TRACE

When this is set to YES a human readable stack trace (with function names and line numbers) is added to the output of the description method of a raised exception object.
This only works if gnustep was built with support for it using libbfd, so it may not be available on all systems.

When this is set to NO the raw stack trace provided by [NSException-callStackReturnAddresses] is disabled.
The possible reasons for disabling this are:
1. that the feature is implemented using a function of the gcc compiler to provide stack addresses, and the function is buggy on some systems/compiler versions, and will cause a signal to be sent which would crash your program if not caught. The GNUstep code catches the signal and recovers using a signal handler, but there have been two reports of this not working with no known cause.
2. that you have code which uses exceptions in a way in which they were not designed to be used ... so that they are routinely and frequently called rather than being called only occasionally when exceptional conditions occur. In this case you may want to disable the stack frame generation implicit in each raised exception, in order to improve performance.

When this is not set, or is set to a non-boolean value, the stack trace handling on exceptions is MacOS-X compatible ... stack return addresses are available but a human readable trace back is not logged.

GNUSTEP_STRING_ENCODING

This is used to specify the default encoding for 8-bit strings (those used by 'cstring' methods of NSString).
It may be any of the 8-bit encodings supported by your system.

If this environment variable is not set, GNUstep attempts to use the characterset specified by your operating systems, locale information (using the standard nl_langinfo function) if possible.

If there is no usable operating system defined characterset, GNUstep defaults to NSISOLatin1StringEncoding.

GNUSTEP_HOST_CPU

Used in place of GNUSTEP_TARGET_CPU if the other is missing.

GNUSTEP_HOST_DIR

Used in place of GNUSTEP_TARGET_DIR if the other is missing.

GNUSTEP_HOST_OS

Used in place of GNUSTEP_TARGET_OS if the other is missing.

GNUSTEP_TARGET_CPU

Overrides the default value of the machine (hardware) name used on this system.

GNUSTEP_TARGET_DIR

Overrides the default path used to locate subdirectories for GNUstep binaries withing bundles and applications. This is normally equivalent to a path made up of the GNUSTEP_TARGET_CPU and GNUSTEP_TARGET_OS

GNUSTEP_TARGET_OS

Overrides the default value of the operating system name used on this system.

GNUSTEP_TZ

Used to specify the timezone to be used if there is no timezone specified in the user defaults system. The preferred mechanism is to use the 'Local Time Zone' value from the user defaults system.

GNUSTEP_CONFIG_FILE

This functionality may have been disabled if the base library was configured/built with the --disable-environment-config-file option.
If it is operational (ie unless you've deliberately disabled it), the environment variable overrides the normal path to the gnustep config file used to determine the locations of paths for the gnustep system (see later).
This is provided to support situations such as when you install into a sandbox during packaging, or where you may want to simultaneously run applications using different sets of resources but linked to a single copy of the base library, or you want to use an alternative config file for some reason.

GNUSTEP_BEHAVIOR_DEBUG
A boolean (YES or NO) which can be used to turn on debug logging (to stderr) of the GSObjCRuntime functions to add/override methods in a class using a list of methods from another class.
HOMEDRIVE

Used on ms-windows to locate the home directory if the HOMEPATH environment variable is also used.

HOMEPATH

Used on ms-windows to locate the home directoryb in conjunction with HOMEDRIVE. If this is just a backslash then the USERPROFILE variable is used if possible.

LANGUAGES

If there is no NSLanguages user default set, and there is no language information available in the native system locale mechanism, then this environment variable is used to provide a list of the languages that the user prefers to use. languages listed in this variable must be separated by semicolons.

LOGNAME

This is used as the default value for the current user (as returned by the NSUserName() functions). If it is not specified, or contains an illegal value, other methods are used to get the user name.

LIBRARY_COMBO

Used to override the default value of the combination of standard libraries used to build binaries. This value locates the final subdirectory used to locate binaries.

NSDeallocateZombies

This may be used in conjunction with NSZombieEnabled to specify whether the objects should really be deallocated. If you set this to YES, the zombie logging will only work until the deallocated memory is re-used.

NSZombieEnabled

If this is set to YES, then deallocation of an object causes the object to be morphed into a Zombie ... a special object which will call the GNUstep specific GSLogZombie() function to log the method call.
If GNUstep-base was built for debugging (make debug=yes), you can set a breakpoint in this function and examine the process memory when you are running under a debugger.
As this overrides actual object deallocation, all memory allocated for objects will be leaked unless the NSDeallocateZombies environment variable is also set.
You can use the CRASH_ON_ZOMBIE environment variable to force an abort after the message is logged.

SOCKS5_SERVER

Specifies the default socks server to be used when making outgoing tcp/ip connections using NSFileHandle. This may also specify a port after the host name (and separated from it by a colon).
This environment variable is used only if the GSSOCKS user default is not set.

SOCKS_SERVER

Equivalent to SOCKS5_SERVER, but used only if that is not defined.

TZ

Used to specify the timezone to be used if there is no timezone specified by any other mechanism. The preferred mechanism is to use the 'Local Time Zone' value from the user defaults system.