2.2. Compiling Hello World

To compile use:

gcc -Wall -g helloworld.c -o helloworld `pkg-config --cflags gtk+-2.0` \
`pkg-config --libs gtk+-2.0`

This uses the program pkg-config, which can be obtained from www.freedesktop.org. This program reads the .pc which comes with GTK to determine what compiler switches are needed to compile programs that use GTK. pkg-config --cflags gtk+-2.0 will output a list of include directories for the compiler to look in, and pkg-config --libs gtk+-2.0 will output the list of libraries for the compiler to link with and the directories to find them in. In the above example they could have been combined into a single instance, such as pkg-config --cflags --libs gtk+-2.0.

Note that the type of single quote used in the compile command above is significant.

The libraries that are usually linked in are:

• The GTK library (-lgtk), the widget library, based on top of GDK.

• The GDK library (-lgdk), the Xlib wrapper.

• The gdk-pixbuf library (-lgdk_pixbuf), the image manipulation library.

• The Pango library (-lpango) for internationalized text.

• The gobject library (-lgobject), containing the type system on which GTK is based.

• The gmodule library (-lgmodule), which is used to load run time extensions.

• The GLib library (-lglib), containing miscellaneous functions; only g_print() is used in this particular example. GTK is built on top of GLib so you will always require this library. See the section on GLib for details.

• The Xlib library (-lX11) which is used by GDK.

• The Xext library (-lXext). This contains code for shared memory pixmaps and other X extensions.

• The math library (-lm). This is used by GTK for various purposes.