The GLib is a library of useful functions and definitions available for use when creating GDK and GTK applications (as a matter of fact it is worth to use GLib functions in all applications if the GLib library is available). It provides replacements for some standard C library (libc) functions, such as malloc(), which are buggy on some systems.
It also provides routines for handling:
Doubly-linked lists, memory allocation and string handling functions are commonly used in Osiris.
Please note that there are many redefined basic data-types such as gint - to replace int, gchar - to replace char or gint8, gint32 to exactly specify the ranges, and many, many more. It is done to preserve compatibility among many hardware and software platforms the GTK works on.