To compile a GTK application, you need to tell the compiler where to find the GTK 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 gtk4
 -pthread -I/usr/include/gtk-4.0 -I/usr/lib64/gtk-4.0/include -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12
$ pkg-config --libs gtk4
 -pthread -lgtk-4 -lgdk-4 -lgio-2.0 -lpangoft2-1.0 -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lcairo -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0 -lgmodule-2.0 -lgthread-2.0 -lrt -lglib-2.0

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 GTK Hello, World, you would type the following:

$ cc `pkg-config --cflags gtk4` hello.c -o hello `pkg-config --libs gtk4`

Deprecated GTK 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 GDK_DISABLE_DEPRECATION_WARNINGS by using the commandline option -DGDK_DISABLE_DEPRECATION_WARNINGS.

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

Here is how you would compile hello.c if you want to allow it to use symbols that were not deprecated in 4.2:

$ cc `pkg-config --cflags gtk4` -DGDK_VERSION_MIN_REQUIRED=GDK_VERSION_4_2 hello.c -o hello `pkg-config --libs gtk4`

And here is how you would compile hello.c if you don’t want it to use any symbols that were introduced after 4.2:

$ cc `pkg-config --cflags gtk4` -DGDK_VERSION_MAX_ALLOWED=GDK_VERSION_4_2 hello.c -o hello `pkg-config --libs gtk4`

The older deprecation mechanism of hiding deprecated interfaces entirely from the compiler by using the preprocessor symbol GTK_DISABLE_DEPRECATED is still used for deprecated macros, enumeration values, etc. To detect uses of these in your code, use the commandline option -DGTK_DISABLE_DEPRECATED. There are similar symbols GDK_DISABLE_DEPRECATED, GDK_PIXBUF_DISABLE_DEPRECATED and G_DISABLE_DEPRECATED for GDK, GdkPixbuf and GLib.