This is pretty awesome.
GNOME itself is all written in pure C using glib, which also contains GObject, a beautiful OOP approach for the C programming language. It has a dynamic type system, supports meta programming...
Very few people know it, but GNOME's GTK interface is fully object oriented, and BTW when you click a GTK button you are clicking on an instance of the class GtkButton that inherits from GtkBin which inherits from GtkWidget. it's a beautiful thing!
Also because GObject is based on a lot of conventions it makes really easy to generate bindings to other programming languages automatically, so basically you can write you library in C with OOP approach using GObject, and for free you get your library easily bound to python, ruby, js or any other language.