Compiling GLib Applications

Compiling GLib Applications

To compile a GLib application, you need to tell the compiler where to find the GLib header files and libraries. This is done with the pkg-config utility.

The following interactive shell session demonstrates how pkg-config is used (the actual output on your system may be different):

$ pkg-config --cflags glib-2.0
-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include
$ pkg-config --libs glib-2.0
-L/usr/lib -lm -lglib-2.0

See the pkg-config website for more information about pkg-config.

If your application uses or GObject features, it must be compiled and linked with the options returned by the following pkg-config invocation:

$ pkg-config --cflags --libs gobject-2.0

If your application uses modules, it must be compiled and linked with the options returned by one of the following pkg-config invocations:

$ pkg-config --cflags --libs gmodule-no-export-2.0
$ pkg-config --cflags --libs gmodule-2.0

The difference between the two is that gmodule-2.0 adds --export-dynamic to the linker flags, which is often not needed.

The simplest way to compile a program is to use the “backticks” feature of the shell. If you enclose a command in backticks (not single quotes), then its output will be substituted into the command line before execution. So to compile a GLib Hello, World, you would type the following:

$ cc `pkg-config --cflags glib-2.0` hello.c -o hello `pkg-config --libs glib-2.0`

Deprecated GLib functions are annotated to make the compiler emit warnings when they are used (e.g. with GCC, you need to use the -Wdeprecated-declarations option). If these warnings are problematic, they can be turned off by defining the preprocessor symbol GLIB_DISABLE_DEPRECATION_WARNINGS by using the commandline option -DGLIB_DISABLE_DEPRECATION_WARNINGS

GLib deprecation annotations are versioned; by defining the macros GLIB_VERSION_MIN_REQUIRED and GLIB_VERSION_MAX_ALLOWED, you can specify the range of GLib versions whose API you want to use. APIs that were deprecated before or introduced after this range will trigger compiler warnings.

Since GLib 2.62, the older deprecation mechanism of hiding deprecated interfaces entirely from the compiler by using the preprocessor symbol G_DISABLE_DEPRECATED has been removed. All deprecations are now handled using the above mechanism.

The recommended way of using GLib has always been to only include the toplevel headers glib.h, glib-object.h, gio.h. Starting with 2.32, GLib enforces this by generating an error when individual headers are directly included.

Still, there are some exceptions; these headers have to be included separately:

  • gmodule.h
  • glib-unix.h
  • glib/gi18n-lib.h or glib/gi18n.h (see the section on Internationalization)
  • glib/gprintf.h and glib/gstdio.h (we don’t want to pull in all of stdio)