Version: $Revision: 1.42 $
Date: $Date: 2011/09/29 23:38:10 $
Copyright: (C) 2005 Free Software Foundation, Inc.
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.
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 compatiblity 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.
Adding an option to a makefile to define one of the following preprocessor constants will modify the API visible to software being compiled -
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.
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.
Setting the user default
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
On mswindows, where syslog does not exist, this flag instead controls whether log/debug output is sent to the windows event log.
Setting the user default
YES will cause NSLog and debug output to
include the current thread in the logged message.
This is useful for debugging multi-threaded applications.
Setting the user default
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.
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.
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.
Used to specify the name of the timezone to be used by the NSTimeZone class.
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.
An array of strings that lists the users prefered languages, in order or preference. If not found the default is just English.
There are some environment variables used by GNUstep base, where there would be problems obtaining data from the defaults system.
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.
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
By default, the program will attempt to continue.
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.
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.
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 didsabled.
The possible reasons for disabling this are:
1. that the feature is implemented using a function of the gcc complier 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 frquently 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 exceptionsis MacOS-X compatible ... stack return addresses are available but a human readable traceback is not logged.
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.
Used in place of GNUSTEP_TARGET_CPU if the other is missing.
Used in place of GNUSTEP_TARGET_DIR if the other is missing.
Used in place of GNUSTEP_TARGET_OS if the other is missing.
Overrides the default value of the machine (hardware) name used on this system.
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
Overrides the default value of the operating system name used on this system.
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.
This functionality may have been disabled if the base library
was configured/built with the
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 sndbox 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.
Used on ms-windows to locate the home directory.
Used on ms-windows to locate the home directory.
If there is no NSLanguages user default set, and there is no language infromation 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.
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.
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.
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.
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.
You can set a breakpoint in this function and examine the process memory if you are running under a debugger.
As this overrides actual object deallocation, all memory allocated for objects will be leaked!
You can use the
variable to force an abort afdter the message is logged.
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 spearated
from it by a colon).
This environment variable is used only if the GSSOCKS user default is not set.
Equivalent to SOCKS5_SERVER, but used only if that is not defined.
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.
This file is the master configuration file for GNUstep. It
can be used to set the base location of all the standard
paths that GNUstep programs use or know about. The
location of this file depends on how the Base library was
configured and/or what operating system it was configured
on. On a GNU/Linux system, the default would be
/etc/GNUstep/GNUstep.conf for instance, while on mswindows
it would be ./GNUstep.conf.
The location of this file can be specified when the base library is configured ... using the
option of the
The configuration file is not actually required to exist, and if it does not exist, then default values will be used. for the standard path locations (these default values may be specified using the
option of the
If you want to force the internal defaults to be used, you can use
--with-config-file= to specify a path
with a trailing '/' (ie with no filename) as the base library
will refrain from trying to load configuration from a file
of no name.
System paths are defined by the following:
In addition to the above SYSTEM domain paths, there are
corresponding LOCAL, NETWORK, and USER domain paths (with the
same names except for replacing 'SYSTEM' with 'LOCAL', 'NETWORK',
All these paths must be absolute, except for the USER domain paths which, if not absolute, are considered to be with the user's home directory.
NB. as a special case a path may begin with './' or '../' when it is to be resolved to an absolute path relative to the location of the GNUstep configuration file. So while such paths appear to be relative, they actually produce absolute locations at runtime since the location of the configuration file is known.
Finally, for paths in the USER domain only, a limited substitution into the path is performed at runtime as follows:
'%u' is replaced by the user name
'%i' is replaced by the user ID
'%%' is replaced by a single '%'
Other paths for each user are defined by the following:
The user's home directory is taken to be the standard
home directory for that user on the system
On unix, that is the user's home directory from the password file, while on windows it's the value given by the HOMEDRIVE and HOMEPATH environment variables (or the USERPROFILE environment variable if the others can't be used).
All the above values from the configuration file are made
available in the NSUserDefaults system at runtime, in the
GSConfigDomain (along with any defaults provided in property
lists in the GlobalDefaults subdirectory or in the
GlobalDefaults.plist file in the same directory as the
.plist files in the GlobalDefaults
subdirectory are merged into the defaults system in an
unpredictable order, but the values from the
GlobalDefaults.plist are merged in after the
other values and will take precedence.
The global defaults files allow packagers and system administrators to provide defaults settings for all users of a particular GNUstep installation.
It is recommended that each software package provides its own defaults in the GlobalDefaults subdirectory, while the GlobalDefaults.plist file should be reserved for other system-wide settings.
The exact format of the configuration file is expected to
be that of a basic unix "conf" style file, with one
key = value per line (the format a unix shell
can 'source' in order to define shell variables).
This configuration file uses the escape sequence and quoting conventions of the standard bourne shell.
The only Keys permitted are those listed above, and all consist of uppercase letters, digits, and underscores, and must not begin with a digit.
A value may be any quoted string (or an unquoted string containing no white space).
Lines beginning with a hash '#' are deemed comment lines and ignored.
The backslash character may be used as an escape character anywhere in the file except within a singly quoted string (where it is taken literally).
A backslash followed immediately by a newline (except in a singly quoted string) is removed completely along with the newline ... it thus serves to join lines so that they are treated as a single line.
NB. Since ms-windows uses backslash characters in paths, it is a good idea to specify path values in the config file as singly quoted strings to avoid having to double all occurrences of the backslash.
The configuration files system has two features which make it possible to build standalone packages containing the entire GNUstep system in a form which can be moved anywhere and just run.
Firstly, variables in the configuration file which define
paths, are expected to by full path specifications, except
for the special case in which they begin with dot-slash (./)
or dot-dot-slash (../).
In this case the path from the variable is appended to the path of the directory containing the configuration file (or the path specified to contain the configuration file if no configuration file exists) to form the value used.
So, if you configure other paths relative to the configuration file, you can relocate everything when you move the configuration file.
Secondly, If the value of the path built in to the base library
as the location of the config file (or specified by
the GNUSTEP_CONFIG_FILE environment variable unless that option
was disabled when the base library was configured)
begins with a dot-slash (./) or dot-dot-slash (../) then the path
used for that file is made relative to the base library.
The base library contains code to determine its own location, so this allows it to locate the configuration file, and by reading the configuration file it determines where all other resources are located.
So you can bundle the whole lot together in one directory, and configure various relative paths in that directory, then move the directory around wherever you like.
If you wish to lock down a production system for
distribution so that users can't change the config
file and mess up paths, you can specify the config file name as
a path with a trailing slash so that the base library will
not read it, and will use the builtin default values.
To do this, you would configure using options like
--with-default-config=myConfig where myConfig
is a file containing the paths you want to use in the locked down
The paths from that file will be built in to the base library as defaults, and library will use them rather than attempting to read a config file at runtime.
You can lock down a relocatable system by using this procedure with './' as the config file path and relative paths in myConfig... a user could then move the entire package around, but would not be able to edit a configuration file to alter the paths within the pacakge.
The user specific configuration file is read after the system
configuration file and may generally override values from the
main file. To prevent the use specific file from being read,
the system manager may define GNUSTEP_USER_CONFIG_FILE in the
main file to be an empty string.
In any case, the user specific file is not read if a program is running setuid.
Unless disabled (as specified above) the presence of a
.GNUstep.conf file in a users home
directory permits the user to customize file locations using all
the same commands as the system directory, though any attempt
to redefine GNUSTEP_USER_CONFIG_FILE is of course ignored.
Attempts to redefine the users home directory at this level are also ignored.
The defaults database for a user is stored in the
subdirectory of the users home directory given by
GNUSTEP_USER_DEFAULTS_DIR (by default, the
On mswindows this may be set to be ':REGISTRY:' to have defaults
stored in the windows registry rather than in the standard file
On any system this may be set to ':INTERNAL:' to use only internal defaults domains (NSArgumentDomain, NSRegistrationDomain, and GSConfigDomain).