Section: GGI (7)
: Handy, portable wrappers for several basic OS features
provides a portable, unified interface to various very basic
operating system features, making it easy to write portable programs without
locking the author into a restricted, bloated, or overbearing development
paradigm. By abstracting the most commonly used functionality in an
operating-system-independent fashion, relying on prepackaged LibGG
distributions can also can reduce the complexity involved in maintaining
a portability suite (e.g. autotools) for the application's development.
Originally LibGG came into being as part of the GGI Project, when
LibGII input functionality was separated from LibGGI into a stand-alone
library, and a place was needed to put functions needed by both libraries.
(Since then, we have forgotten what "GG" stood for, so don't ask.)
The master upstream source of LibGG is still distributed as part of
LibGII, however it is itself a separately-distributable stand-alone
package of utilities that can be very useful to applications developers.
LibGG provides the following groups of functions and/or macros. Some
may not be possible to implement on some operating systems, some may
be possible, just nobody has done so yet. We try to make them all
available where we can find the time and expertise:
Time functions (ggCurTime(3), ggUSleep(3) and ggUSlumber(3)) to handle
high-resolution timing and delays without busy-looping.
Cleanup callbacks (ggRegisterCleanup(3), ggUnregisterCleanup(3),
ggCleanupForceExit(3)) to allow your application to perform emergency
actions before a program is terminated abnormally.
Timer callbacks (ggAddTask(3), ggDelTask(3), ggTimeBase(3)) provide a
(non-realtime) wall-clock periodic/one-shot callback scheduler that can
be shared between many different areas of the application code without
fear of interference.
Locking Functions (ggLock(3), ggLockCreate(3), ggLockDestroy(3), ggTryLock(3),
ggUnlock(3)) which are thread-safe in threaded environments.
System and CPU detection utilities (ggGetSwarType(3), GG_HAVE_INT64,
GG_LITTLE_ENDIAN) to allow you to detect CPU endianness and the
presence of features such as SWAR (SIMD) instruction sets (e.g. MMX),
and to turn on/off or change SWARs for testing or as a workaround.
Very basic overrun-proof string operations (ggstrlcpy(3), ggstrlcat(3))
which are a horrible mess for cross-platform programs to map to
OS-local string functions/headers.
Dynamic symbol management functions (ggGetScope(3), ggDelScope(3),
ggFromScope(3), ggNewScope(3)) allows you to create a plug-in system
where code is either dynamically loaded into and out of your program,
or statically linked in the library or program.
An option parser (ggParseOpts, ggSystemOpts) and plugin configuration
system (ggGetUserDir(3), ggParseTarget, ggLoadConfig(3), ggFreeConfig(3),
ggMatchConfig, ggConfigExpandAlias) which are by-products of the
pluggable module support but can be useful for other things if you like
LibGG provides a few additionnal tools that are used internaly, for
other GGI libraries and that can also be useful to the application
programmer: macros for managing data structures such as lists, queues,
trees, a simple iterator scheme. These features are mostly
The following outlines the environment variables, intended for the
user, which affect the behaviour of LibGG:
LibGG uses the environment variable GG_OPTS, and
expects it to contain a valid option string as documented in the
manpage for ggParseOpts. The available options are documented
along with the LibGG API functions which they most affect.
The debug level for LibGII:
0 or unset : debug output is off; debugging is off
255 : all debug output is on
You may also bitwise 'or' any of the following together:
2 : debug core
4 : misc debugging output
8 : debug locking code
16 : debug task subsystem
32 : debug scope code (dynamic library and symbol lookup)
64 : debug api code (not there yet)
Turn on synchronous debug output, flushing the output buffers
before returning from DPRINT calls.
LibGG requires the exclusive use of one signal under certain
environments. This signal defaults to SIGPROF, where available, but
may be configured through the GG_OPTS option -signum=n
represents the numerical value of the signal to use. This
signal should not be one of the fatal signals handled by the LibGG
cleanup facilities, and must be a signal onto which a handler may be
assigned. Applications should not install handlers or alter the
signal handler in any way for this signal.
There is still some legacy to LibGGI
in some of the namespace,
is currently the real name for
, which is an unofficial new addition destined
to replace it. Deprecation will take a few revisions as it must
be done in an orderly fashion.
Likewise the header file is included as <ggi/gg.h> but we will
probably keep that as-is because of the way LibGG is distributed and
to avoid adding more clutter in system include directories than
Several features are incomplete, for example, code is still needed
to detect SWAR on many of the more obscure architectures.