GLib

Glib is a great library, all in all, providing a great source of easy-to-use libraries in C. It includes many handy features that also make it configurable with options, all tied to other library parts. Glib also has documentation for each of its pieces, designed to be as understandable as possible. The components of Glib are GIO, GThread (for threading purposes), GModule (module structure), and GOject (a system for programming objects)

Made primarily by the GNOME community, Glib is a library-focused project of GTK+ and the aforementioned GNOME but is also available for use by anyone seeking high-quality low-level libraries. The library is, of course, cross-platform, meaning that it can be used by any user on any operating system preferred with components that can be talked separately, also making for a great source of data and system parts.

Glib consists of a few low-level system libraries written in C, and makes for a great choice among other libraries

• Memory chunks, with quite a sufficient capacity, are capable of handling large portions of data
• Hash tables as a data structure for better implementation of an associative array, as well as linked lists for simple linear collection of data
• Asynchronous queues (as well as synchronous) make queuing the chains together much simpler and more efficient 
• Standard (and customizable) macros for better system automatization 
• Dynamic data modules and their load orders make the data stream fast and dynamic 
• Automatic warning of possible errors being made during the creation process
• Cache and history for memory and data management without fear of losing out on lost parts
• Timers of library work and more, handy for anyone in need of time measurement 
• Many more handy features, tricks, and utilities all combined in one piece of software creating a true vacuum of options to choose from!

There are of course many other features implemented but a list would go for much longer if we started listing them all. Also, the different versions of the project deserve a mention, as it also makes a good variety of software and its variants, aspects, and sides. All of this makes Glib truly a classic among C libraries, a great choice for that it seems.