Continuing the development of awesome-c list on GitHub
# awesome-c [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome)[![List Status](https://api.travis-ci.org/aleksandar-todorovic/awesome-c.svg?branch=master)](https://travis-ci.org/aleksandar-todorovic/awesome-c)

A curated list of C good stuff. This list contains *only* [free software](https://en.wikipedia.org/wiki/Free_software) for code, and sellers who aren't evil for physical resources.

**LOOKING FOR MAINTAINERS:** This list is currently pretty much inactive. I'm looking for maintainers that can make it great again. See [#26](https://github.com/aleksandar-todorovic/awesome-c/issues/26) for more info, but the process is simple: add or fix a couple of things in this list and you'll become a contributor to a 850+ stars list.

This list was previously maintained by [@kozross](https://github.com/kozross). He decided to switch the list to a [new platform](https://notabug.org/koz.ross/awesome-c), so I've decided to fork it so we could keep it on GitHub.

Contents
========

## Contents ##

- [Build Systems](#build-systems)
- [Compilers](#compilers)
- [Compiler libraries](#compiler-libraries)
- [Compression](#compression)
- [Crypto](#crypto)
- [Database](#database)
- [Deep Learning](#deep-learning)
- [Documentation Generation](#documentation-generation)
- [Editors](#editors)
- [Embedded Systems](#embedded-systems)
  - [RTOS](#rtos)
- [Environments](#environments)
- [Frameworks](#frameworks)
- [Game Programming](#game-programming)
  - [Engines](#engines)
  - [Resources](#resources)
- [Generic Programming](#generic-programming)
- [Graphics](#graphics)
  - [Graphic APIs](#graphic-apis)
- [Graphical User Interface](#graphical-user-interface)
- [Hashing](#hashing)
- [Image Processing](#image-processing)
- [JSON](#json)
- [Learning, Reference and Tutorials](#learning-reference-and-tutorials)
  - [Online](#online)
      - [Reference](#reference)
        - [Language Standards](#language-standards)
      - [Beginner](#beginner)
      - [Intermediate](#intermediate)
      - [Advanced](#advanced)
      - [Self-study courses](#self-study-courses)
  - [Physical](#physical)
      - [Reference](#reference-1)
      - [Beginner](#beginner-1)
      - [Intermediate](#intermediate-1)
      - [Advanced](#advanced-1)
- [Macros](#macros)
- [Memory Allocators](#memory-allocators)
- [Multimedia](#multimedia)
- [Networking and Internet](#networking-and-internet)
  - [Web Frameworks](#web-frameworks)
- [Numerical](#numerical)
- [Parallel Programming](#parallel-programming)
- [Parsers](#parsers)
- [Regex](#regex)
- [Serialization](#serialization)
- [Source Code Collections](#source-code-collections)
- [Standard Libraries](#standard-libraries)
- [String Manipulation](#string-manipulation)
- [Testing](#testing)
- [Text Editor Extensions](#text-editor-extensions)
  - [Atom](#atom)
  - [Emacs](#emacs)
  - [Vim](#vim)
- [Tools](#tools)
- [Utilities](#utilities)
- [XML](#xml)

## Build Systems ##

These are tools to automate the building and testing of projects in C.

* [aimake](http://nethack4.org/projects/aimake/) - Build tool designed to avoid complex configurations. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Autoconf](https://www.gnu.org/software/autoconf/autoconf.html) - Extensible package of M4 macros that produce shell scripts to automatically configure software source code packages. Part of the Autotools. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Automake](https://www.gnu.org/software/automake/automake.html) - Tool for automatically generating `Makefile.in` files compliant with the GNU Coding Standards. Requires the use of Autoconf. Part of the Autotools. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [CMake](https://cmake.org/) - Tools for cross-platform building, testing, and packaging. [`3-clause BSD`](https://gitlab.kitware.com/cmake/cmake/raw/master/Copyright.txt)
* [Jam](https://www.perforce.com/documentation/jam-documentation) - Build system, designed to be easier than make. Understands C build rules implicitly. [`Jam License`](https://en.wikipedia.org/wiki/Perforce_Jam#License)
* [Libtool](https://www.gnu.org/software/libtool/) - Generic library support script. Part of the Autotools. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Meson](https://mesonbuild.com/) - Extremely fast, user-friendly build system. Based on Ninja. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [Premake](https://github.com/premake/premake-core) - Build script generator for toolsets like Visual Studio, Xcode, or GNU Make. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [SCons](https://www.scons.org/) - An easier, more reliable and faster way to build software. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [Ninja](https://github.com/ninja-build/ninja) - Small, simple build system with a focus on speed. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [Bazel](https://bazel.build/) - Build system for various operating systems and targets. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [Buck](https://buck.build/) - Build system created and used by Facebook. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [Qbs](https://doc.qt.io/qbs/) - Modern build tool for software projects. [`LGPL3`](https://code.qt.io/cgit/qbs/qbs.git/tree/LICENSE.LGPLv3)
* [qmake](https://doc.qt.io/qt-5/qmake-manual.html) - Build system included with the Qt Framework. [`GNU GPL3 with Qt Exception`](https://github.com/qt/qtbase/blob/5.11/LICENSE.GPL3-EXCEPT)
* [xmake](https://xmake.io/) - Cross-platform build utility based on lua. [`Apache 2.0`](https://github.com/xmake-io/xmake/blob/master/LICENSE.md )

## Compilers ##

* [Clang](http://clang.llvm.org/) - C compiler for LLVM. Supports C11. [`NCSA`](https://directory.fsf.org/wiki/License:NCSA)
* [CompCert](http://compcert.inria.fr/) - Fully-verified C compiler. Supports almost all of C89. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [GCC](https://gcc.gnu.org/) - Provides a C compiler as part of its compiler set. Supports C11 and OpenMP. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [PCC](http://pcc.ludd.ltu.se/) - Venerable C compiler. Supports C99. [`Various free licenses`](http://pcc.ludd.ltu.se/licenses/)
* [TCC](https://bellard.org/tcc/) - Tiny C Compiler; a small, fast C compiler. Supports C99 (except complex types). [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [Intel SPMD](http://ispc.github.io/) - Compiler for a variant of the C language, for single program, multiple data programming. [`Various licenses`](https://github.com/ispc/ispc/blob/master/LICENSE.txt)
* [ccache](https://ccache.dev/) - Compiler cache designed to speedup recompilation. [`GNU GPL3 or later`](https://ccache.dev/license.html)

## Compiler libraries ##

Libraries for use in compilers, interpreters, and low-level based projects.

* [yasm](http://yasm.tortall.net/) - Yasm Modular Assembler Project. [`2-clause BSD`](https://directory.fsf.org/wiki/License:BSD-2-Clause)

## Compression ##

* [libzip](https://libzip.org/) - A C library for reading, creating, and modifying zip archives. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [lzo](http://www.oberhumer.com/opensource/lzo/) - Very fast data compression library. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [zlib](http://zlib.net/) - Massively-spiffy yet delicately-unobtrusive compression library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [bzip2](http://www.bzip.org/) - Patent free, high quality data compressor. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [lz4](https://lz4.github.io/lz4/) - Fast Compression algorithm.
* [snappy](https://github.com/google/snappy) - Fast compression library (implementation in C++, native bindings to C).
* [zstd](http://facebook.github.io/zstd/) - Fast real-time compression algorithm [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [brotli](https://github.com/google/brotli) - Generic lossless compression algorithm based on LZ77, Huffman coding and 2nd order context modelling [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [quicklz](http://www.quicklz.com/index.php) - Fast compression library. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [pixz](https://github.com/vasi/pixz) - Pixz (pronounced pixie) is a parallel, indexing version of `xz`. [`2-clause BSD`](https://directory.fsf.org/wiki/License:BSD-2-Clause)

## Crypto ##

* [GnuTLS](https://www.gnutls.org/) - Secure communication library, implementing SSL, TLS and DTLS. [`GNU LGPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [libgcrypt](https://gnupg.org/related_software/libgcrypt/) - General-purpose cryptography library, with a range of available ciphers. [`GNU LGPL2.1or later (code)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) and [`GNU GPL2.1 or later (manual and tools)`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [OpenSSL](https://www.openssl.org/) - Implementation of the SSL and TLS protocols, and also includes a cryptography library. [`Dual Licensed under the OpenSSL License and the SSLeay License`](https://www.openssl.org/source/license.html)
* [libsodium](https://download.libsodium.org/doc/) - Modern and easy-to-use crypto library. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libtomcrypt](https://www.libtom.net/) - Fairly comprehensive, modular and portable cryptographic toolkit. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [mbed TLS](https://tls.mbed.org/) - Another crypto implementation for C. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [libressl](https://www.libressl.org/) - Modernized fork of OpenSSL. [`Various Licenses`](https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/lib/libssl/LICENSE?rev=1.12)

## Database ##

This lists databases and data stores with C APIs.

* [BerkeleyDB](https://www.oracle.com/database/berkeley-db/) - Library for a high-performance embedded database for key-value data. [`GNU AGPLv3`](https://www.gnu.org/licenses/agpl-3.0.html)
* [Hiredis](https://github.com/redis/hiredis) - Minimalistic client library for Redis. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [LMDB](https://github.com/LMDB/lmdb) - Ultra-fast, ultra-compact key-value embedded data store. [`OpenLDAP License`](https://directory.fsf.org/wiki/License:OLDAP-2.7)
* [MariaDB](https://mariadb.com/) - Robust, scalable and reliable SQL server, designed to be a drop-in replacement for MySQL. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [mongo-c-driver](http://mongoc.org/) - High-performance client library for [MongoDB](https://www.mongodb.com/). [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [PostgreSQL](https://www.postgresql.org/) - Powerful object-relational database system. [`PostgreSQL licence`](https://opensource.org/licenses/postgresql)
* [recutils](https://www.gnu.org/software/recutils/) - Set of tools and a C library for accessing human-editable, plaintext database files called recfiles. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Redis](https://redis.io/) - Advanced key-value store. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [sophia](http://sophia.systems/) - Modern, embeddable key-value database. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [SQLite](https://www.sqlite.org/about.html) - Self-contained, serverless, zero-configuration, transactional SQL database engine with a C interface. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [UnQLite](https://unqlite.org/) - Self-contained, serverless, zero-configuration, transactional NoSQL engine with a C interface. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)

## Deep Learning ##
* [Darknet](https://pjreddie.com/darknet/) - Open source neural network framework written in C and CUDA. It is fast, easy to install, and supports CPU and GPU computation.

## Documentation Generation ##

* [Cxref](http://www.gedanken.org.uk/software/cxref/) - Generates documentation of C programs in either LaTeX, HTML, RTF or SGML. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [DocOnce](https://hplgit.github.io/doconce/doc/web/index.html) - Modestly-tagged markup language that can be used to generate a range of formats. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [Doxygen](http://www.doxygen.nl/) - The de-facto standard tool for generating C documentation from annotated sources. Can generate a large range of formats. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [GTK-Doc](https://www.gtk.org/gtk-doc/) - Tool for generating C documentation from annotated sources. Has support for the Autotools. [`GNU GPL2.1 (code)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`GNU FDL1.1`](https://www.gnu.org/licenses/old-licenses/fdl-1.1.html)

## Editors ##

These are specifically fancier, IDE-type editors. If you want a programmer's text editor, look elsewhere. Besides, whatever choice you make most likely supports C anyway.

* [Anjuta DevStudio](http://anjuta.org/) - The GNOME IDE. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [Atom](https://atom.io/) - Hackable text editor for the 21st century. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [Code::Blocks](http://www.codeblocks.org/) - Extensible, configurable IDE supporting C. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [CodeLite](https://codelite.org/) - Cross-platform IDE. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Eclipse](http://www.eclipse.org/ide/) - IDE written in Java. [`EPL`](https://directory.fsf.org/wiki/License:EPL-1.0)
* [Geany](https://www.geany.org/) - Very small and fast IDE. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [KDevelop](https://www.kdevelop.org/) - The KDE IDE. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Qt Creator](https://www.qt.io/qt-features-libraries-apis-tools-and-ide/#ide) - Cross-platform IDE written with C++ and Qt, part of the Qt SDK. Supports Clang Code Model. [`GNU GPL3 with Qt exception`](https://github.com/qt-creator/qt-creator/blob/master/LICENSE.GPL3-EXCEPT)
* [Visual Studio Code](https://code.visualstudio.com/) - Code editing, redefined. Visual Studio Code.

## Embedded Systems ##

These are projects that allow one to work with microcontrollers and other resource constrained architectures.

### RTOS ###

A real-time operating system (RTOS) is intended to serve real-time applications that process data with low latency delay.

* [Amazon FreeRTOS](https://aws.amazon.com/freertos/) - RTOS for microcontrollers that makes small, low-power edge devices easy to program. [`MIT`](https://github.com/aws/amazon-freertos/blob/master/LICENSE)
* [ChibiOS](http://www.chibios.org/dokuwiki/doku.php) - RTOS with complete development environment (HAL, drivers, support files, and tools). [`Various Licenses`](http://www.chibios.org/dokuwiki/doku.php?id=chibios:licensing:start)
* [Contiki](http://www.contiki-os.org/) - Connect low-cost, low power microcontrollers to the Internet. [`3-clause BSD`](https://github.com/contiki-os/contiki/blob/master/LICENSE)
* [Zephyr Project](https://www.zephyrproject.org/) - Scalable real-time RTOS supporting multiple hardware architectures, optimized for resource constrained devices. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [RIOT OS](https://www.riot-os.org/) - Real-time multi-threading operating system that supports a range of devices that are typically found in the Internet of Things. [`LGPL-2.1`](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html)

## Environments ##

This is a list of technologies designed to bring Windows into the 21st century with respect to support for C.

* [Cygwin](https://cygwin.com/) - Designed to emulate a POSIX-compatible environment extensively under Windows. [`Various Licenses`](https://cygwin.com/licensing.html)
* [MinGW-w64](http://mingw-w64.yaxm.org/doku.php/start) - Minimalist environment for C development on Windows with 64 bit support. [`Various Licenses`](http://mingw.org/license)

## Frameworks ##

This section has big libraries that provide data structures and other stuff you expect of a 'modern' standard library.

* [APR](http://apr.apache.org/) - Apache Portable Runtime; another library of cross-platform utility functions. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [C Algorithms](https://fragglet.github.io/c-algorithms/) - Collection of common algorithms and data structures for C. [`ISC`](https://directory.fsf.org/wiki/License:ISC)
* [C Macro Collections](https://github.com/LeoVen/C-Macro-Collections) - Header only, macro generated, generic and type-safe Collections in C. [`MIT`](https://spdx.org/licenses/MIT.html)
* [CPL](http://www.eso.org/sci/software/cpl/) - The Common Pipeline Library; a set of libraries designed to be a comprehensive, efficient and robust software toolkit. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [EFL](https://www.enlightenment.org/) - Large collection of useful data structures and functions.
* [GLib](https://wiki.gnome.org/Projects/GLib) - Library of utility functions and structures, designed to be portable, efficient and powerful. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [GIO](https://developer.gnome.org/gio/) - Modern and easy-to-use VFS API. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [GObject](https://developer.gnome.org/gobject/stable/) - Object-oriented system and object model for C. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [libnih](https://github.com/keybuk/libnih) - Lightweight library of C functions and structures. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [libU](http://www.koanlogic.com/libu/) - Small library of basic utilities, including memory allocation, string manipulation and logging. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [PBL](http://www.mission-base.com/peter/source/) - Large library of utilities, featuring data structures, among other things. [`GNU LGPL2.1 or later (library)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`GNU GPL2.1 or later (test code)`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [qlibc](http://wolkykim.github.io/qlibc/) - Simple and powerful C library, designed as a replacement for GLib while focusing on being small and light. [`qLib license`](https://github.com/wolkykim/qlibc/blob/master/LICENSE) (similar to [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD))
* [stb](https://github.com/nothings/stb) - Range of single-file libraries for C. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [libsrt](https://faragon.github.io/libsrt.html) - Safe Real-Time library for C. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)


## Game Programming ##

### Engines ###

These are provided as examples of C game programming code.

* [Corange](https://github.com/orangeduck/Corange) - Game engine in pure C. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [Darkplaces](https://icculus.org/twilight/darkplaces/) - Modified version of the Quake2 engine. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [ioquake3](https://ioquake3.org/) - The Quake3 engine, freed at last. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Orx](http://orx-project.org/) - Portable, lightweight, plugin-based, data-driven, 2D-oriented game engine. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [Quake](https://github.com/id-Software/Quake) - The Quake engine. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Quake2](https://github.com/id-Software/Quake-2) - The Quake2 engine. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Spearmint](https://clover.moe/spearmint/) - Engine designed for FPS games. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)

### Resources ###

These are libraries of all sorts that are useful for game programming.

* [Allegro](https://liballeg.org/) - Cross-platform, video game development and multimedia library. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [Chipmunk2D](http://chipmunk-physics.net/) - Fast and lightweight 2D game physics library. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [CSFML](https://www.sfml-dev.org/download/csfml/) - Binding for [SFML](https://www.sfml-dev.org/index.php) in C. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [FreeGLUT](http://freeglut.sourceforge.net/) - Alternative to the OpenGL Utility Toolkit. Allows the creation and management of windows with OpenGL contexts. [`X11`](https://directory.fsf.org/wiki/License:X11)
* [GLFW](https://www.glfw.org/) - Multi-platform library for creating windows with OpenGL contexts. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [libao](https://xiph.org/ao/) - Cross-platform audio library with a wide variety of outputs. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [RetroArch](https://www.libretro.com/) - The reference frontend for [libretro](https://www.libretro.com/). [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [SDL and SDL2](https://www.libsdl.org/) - Cross-platform development library designed to provide low-level access to audio, keyboard, mouse, joystick and graphics hardware via OpenGL. SDL2 is the most current version. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [raylib](https://www.raylib.com/) - Simple and easy-to-use library to learn videogames programming. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)

## Generic Programming ##

* [klib](http://attractivechaos.github.io/klib/#About) - Small and lightweight implementations of common algorithms and data structures. [`MIT`](https://en.wikipedia.org/wiki/MIT_License)

## Graphics ##

* [Cairo](https://www.cairographics.org/) -2D graphics library. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`MPLv1.1`](https://directory.fsf.org/wiki/License:MPL-1.1)
* [Cogl](https://github.com/rib/cogl-web/wiki) - GPU graphics and utilities API. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [Clutter](https://blogs.gnome.org/clutter/get-it/) - UI library based on OpenGL. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [giflib](https://sourceforge.net/projects/giflib/) - Library for reading and writing gif images. [`MIT`](https://spdx.org/licenses/MIT.html)
* [heman](https://github.com/prideout/heman) - Tiny library of image utilities dealing with height maps, normal maps, distance fields and the like. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libcaca](https://github.com/cacalabs/libcaca) - ASCII renderer for terminal-based interfaces. [`WTFPLv2`](http://www.wtfpl.net/txt/copying/)
* [libimagequant](https://pngquant.org/lib/) - Small, portable library for high-quality conversion of RGBA images to 8-bit indexed colour images. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [libjpeg-turbo](https://libjpeg-turbo.org/) - Faster library for reading and writing JPEG files. [`Various Licenses`](https://libjpeg-turbo.org/About/License)
* [libpng](http://www.libpng.org) - The official PNG reference library. [`libpng license`](http://www.libpng.org/pub/png/src/libpng-LICENSE.txt)
* [libxmi](https://www.gnu.org/software/libxmi/) - Function library for rasterizing 2D vector graphics. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [mozjpeg](https://github.com/mozilla/mozjpeg) - Improved JPEG encoder. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)

### Graphic APIs ###

* [OpenGL](https://www.opengl.org/) - Industry adopted 2D and 3D graphics API. More resources at [awesome-opengl](https://github.com/eug/awesome-opengl).
* [OpenGL ES](https://www.khronos.org/opengles/) - Industry adopted 2D and 3D graphics API for mobile and embedded devices.
* [OpenGL SC](https://www.khronos.org/openglsc/) - Graphic and compute standard for industry requiring system safety certification.
* [Vulkan](https://www.khronos.org/vulkan/) - Explicit graphic and compute API for modern cross-platform development. More resources at [awesome-vulkan](https://github.com/vinjn/awesome-vulkan).

## Graphical User Interface ##

These are specifically [widget toolkits](https://en.wikipedia.org/wiki/Widget_toolkit).

* [GTK+](https://www.gtk.org/) - Cross-platform widget toolkit. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [IUP](http://webserver2.tecgraf.puc-rio.br/iup/) - Another cross-platform widget toolkit. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [Tk](http://www.tcl.tk/) - Basic widget toolkit. Part of Tcl/Tk. [`Tcl/Tk License`](http://www.tcl.tk/software/tcltk/license.html)
* [XForms Toolkit](http://xforms-toolkit.org/) - Widget toolkit designed for the XWindow system. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [nuklear](https://github.com/vurtun/nuklear) - Single-header ANSI C gui library. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [libui](https://github.com/andlabs/libui) - Simple and portable (but not inflexible) GUI library. [`MIT`](https://github.com/andlabs/libui/blob/master/LICENSE)
* [LCUI](https://github.com/lc-soft/LCUI/) - Small C library for building user interfaces with C, XML and CSS. [`MIT`](https://github.com/lc-soft/LCUI/blob/develop/LICENSE.TXT)

## Hashing ##

All hashing related libraries, cryptographic or not.

* [jwHash](https://github.com/watmough/jwHash) - Fast hashtable implementation. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [xxHash](http://cyan4973.github.io/xxHash/) - Extremely fast non-cryptographic hash algorithm. [`2-clause BSD`](https://directory.fsf.org/wiki/License:BSD-2-Clause)
* [libcrc](https://github.com/PeterScott/murmur3) - Multi platform CRC library. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [murmur](https://github.com/ispc/ispc) - C implementation of MurMur Hashing. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [t1ha](https://github.com/leo-yuriev/t1ha) - Fast Positive Hash library. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)

## Image Processing ##

* [libccv](http://libccv.org) - Modern Computer Vision Library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)

## JSON ##

* [Jansson](http://www.digip.org/jansson/) - C library for encoding, decoding and manipulating JSON. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [jsmn](https://zserge.com/jsmn.html) - Minimalistic JSON parser. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [json-c](https://github.com/json-c/json-c/wiki) - Library for working with JSON. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [parson](https://github.com/kgabis/parson) - Lightweight JSON library written in C. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [WJElement](https://github.com/netmail-open/wjelement/wiki) - Advanced JSON manipulation library, with support for JSON Schema. [`LGPL, any version`](https://github.com/netmail-open/wjelement/)
* [YAJL](https://lloyd.github.io/yajl/) - Fast C JSON streaming parser library. [`ISC`](https://directory.fsf.org/wiki/License:ISC)

## Learning, Reference and Tutorials ##

This is a list of resources for learning C programming in general, or something useful relating to C programming.

### Online ###

#### Reference ####

* [SEI CERT C Coding Standard](https://wiki.sei.cmu.edu/confluence/display/c/SEI+CERT+C+Coding+Standard)
* [C FAQ - comp.lang.c Frequently Asked Questions](http://c-faq.com/)
* [Comparison of C/POSIX standard library implementations for GNU/Linux](http://www.etalabs.net/compare_libcs.html)
* [GNU C Reference Manual](https://www.gnu.org/software/gnu-c-manual/)
* [Robert Pike's notes on programming in C](http://www.lysator.liu.se/c/pikestyle.html)
* [Draft ANSI C Rationale](http://port70.net/~nsz/c/c89/rationale/)
* [Draft C99 Rationale](http://port70.net/~nsz/c/c99/C99RationaleV5.10.pdf)

##### Language Standards #####
* [Draft ANSI C (C89) standard](http://port70.net/~nsz/c/c89/c89-draft.txt)
* [Draft C99 standard](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf)
* [Draft C11 standard](http://www.open-std.org/JTC1/SC22/WG14/)

#### Beginner ####

* [Tutorial on pointers](http://www.cs.ucsb.edu/~mikec/cs16/misc/ptrtut12/index.htm)
* [Building C Projects](http://nethack4.org/blog/building-c.html)
* [C Programming Wikibook](https://en.wikibooks.org/wiki/C_Programming)
* [Introduction to 'fun' C](https://gist.github.com/eatonphil/21b3d6569f24ad164365)
* [Learning C with GDB](https://www.recurse.com/blog/5-learning-c-with-gdb)
* [POSIX Threads Programming tutorial](https://computing.llnl.gov/tutorials/pthreads/) (a little dated, but most of it is still valid and useful)
* [The GNU C Programming Tutorial](http://www.crasseux.com/books/ctut.pdf) (online PDF)
* [Templating in C](http://blog.pkh.me/p/20-templating-in-c.html)

#### Intermediate ####

* [8 gdb tricks you should know](https://blogs.oracle.com/linux/8-gdb-tricks-you-should-know-v2)
* [10 C99 tricks](https://blog.noctua-software.com/c-tricks.html)
* [Diving into concurrency: trying out mutexes and atomics](https://jvns.ca/blog/2014/12/14/fun-with-threads/)
* [Introduction to OpenMP](https://www.youtube.com/playlist?list=PLLX-Q6B8xqZ8n8bwjGdzBJ25X2utwnoEG) (video)
* [OpenMP tutorial](https://computing.llnl.gov/tutorials/openMP/) (for the OpenMP3 standard)
* [memcpy vs memmove](https://web.archive.org/web/20170620131430/https://www.tedunangst.com/flak/post/memcpy-vs-memmove)
* [MPI tutorial](https://computing.llnl.gov/tutorials/mpi/)
* [Some unknown features or tricks in C language](https://proprogramming.org/some-unknown-features-or-tricks-in-c-language/)
* [The lost art of C structure packing](http://www.catb.org/esr/structure-packing/)
* [What a C programmer should know about memory](https://marek.vavrusa.com/memory/)
* [What every C programmer should know about undefined behaviour](http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html)

#### Advanced ####

* [Advanced metaprogramming in C](http://250bpm.com/blog:56)
* [Quick tutorial on implementing and debugging malloc, free, calloc, and realloc](http://danluu.com/malloc-tutorial/)
* [Bit twiddling hacks](https://graphics.stanford.edu/~seander/bithacks.html)
* [I do not know C](https://kukuruku.co/post/i-do-not-know-c/)
* [Implementing smart pointers for the C programming language](https://snai.pe/c/c-smart-pointers/)
* [Inline functions in C](http://www.greenend.org.uk/rjk/tech/inline.html)
* [Metaprogramming custom control structures in C](https://www.chiark.greenend.org.uk/~sgtatham/mp/)
* [Some dark corners of C](https://docs.google.com/presentation/d/1h49gY3TSiayLMXYmRMaAEMl05FaJ-Z6jDOWOz3EsqqQ/edit?pli=1#slide=id.gaf50702c_0153)
* [Writing efficient C and C code optimization](https://www.codeproject.com/articles/6154/writing-efficient-c-and-c-code-optimization)
* [What every programmer should know about memory](https://www.akkadia.org/drepper/cpumemory.pdf)

#### Self-study courses ####

* [C Programming Language Certified Associate preparation course](https://cppinstitute.com/study-resources )

### Physical ###

#### Reference ####

* [C: A Reference Manual 5E](http://careferencemanual.com/) - Full reference book for C99.
* [C Pocket Reference](http://shop.oreilly.com/product/9780596004361.do) - Concise reference book for C99.
* [The C Programming Language 2E](https://en.wikipedia.org/wiki/The_C_Programming_Language) - The original book on C, by its creators.

#### Beginner ####

* [C Primer Plus 6E](https://www.pearson.com/us/higher-education/program/Prata-C-Primer-Plus-6th-Edition/PGM4399.html) - Complete tutorial on programming in C11.
* [C Programming: A Modern Approach](http://knking.com/books/c2/index.html) - Excellent book to learn the basics of C.
* [Head First C](http://shop.oreilly.com/product/0636920015482.do) - 'Head-first' style book for learning C.

#### Intermediate ####

* [21st Century C](http://shop.oreilly.com/product/0636920033677.do) - Very good *second* programming book on C.
* [Understanding and Using C Pointers](http://shop.oreilly.com/product/0636920028000.do) - In-depth resource on pointers in C.
* [ZeroMQ](http://shop.oreilly.com/product/0636920026136.do) - Book for using ZeroMQ with C.

#### Advanced ####

* [Expert C Programming: Deep C Secrets](https://dl.acm.org/citation.cfm?id=179241) - Interesting, in-depth and *entertaining* look at the innards of C.

## Macros ##

* [P99](http://p99.gforge.inria.fr/) - Suite of macros to implement advanced features like default function arguments, scope-bound resources, etc. (Requires C99) [`Q Public License`](https://tldrlegal.com/license/q-public-license-1.0-(qpl-1.0)#summary)

## Memory Allocators ##

Implementations of memory allocators for various systems and platforms.

* [jemalloc](http://jemalloc.net/) - General purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support, commonly used in production systems. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [dlmalloc](http://g.oswego.edu/pub/misc/malloc.c) - Doug Lea's malloc(3) implementation, useful for academic and research purposes. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [Hoard](http://hoard.org/) - A Fast, Scalable, and Memory-efficient Malloc for Linux, Windows, Mac, and Solaris. [`GNU GPL2`](http://www.gnu.org/licenses/gpl-3.0.html)
* [nedmalloc](http://www.nedprod.com/programs/portable/nedmalloc/) - An EXTREMELY FAST portable thread caching malloc(3) implementation written in C. [`GNU GPL2`](http://www.gnu.org/licenses/gpl-3.0.html)
* [rpmalloc](https://github.com/rampantpixels/rpmalloc) - Cross platform, lock-free memory allocator. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)


## Multimedia ##

* [FFMPEG](https://www.ffmpeg.org/) - Complete, cross-platform solution to record, convert and stream audio and video. [`GNU LGPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`GNU GPL2.1 or later (some parts)`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [GStreamer](https://gstreamer.freedesktop.org/) - Framework for audio and visual media. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [lodepng](https://lodev.org/lodepng/) - Simple PNG image decoder and encoder, requiring no other dependencies. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [libsoup](https://wiki.gnome.org/action/show/Projects/libsoup?action=show&redirect=LibSoup) - GNOME HTTP client/server library. Uses GObject. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [libmpv](https://mpv.io/) - Music-playing library. Compile with ``./waf configure --disable-cplayer --enable-libmpv-shared`` to not have the music player. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [libsoundio](http://libsound.io/) - Library for cross-platform, real-time audio input and output. Has a range of back-ends. [`Expat`](https://directory.fsf.org/wiki/License:Expat)


## Networking and Internet ##

* [asnlc](http://lionet.info/asn1c/compiler.html) - Compiler of ASN.1 specifications into C source code. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [czmq](http://czmq.zeromq.org/) - High-level binding for ZeroMQ. [`MPL2.0`](https://www.gnu.org/licenses/license-list.html#MPL-2.0)
* [GNU adns](https://www.gnu.org/software/adns/) - Advanced, easy-to-use, asynch-capable DNS client library and utilities. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GNU SASL](https://www.gnu.org/software/gsasl/) - Implementation of the Simple Authentication and Security Layer and a few common SASL mechanism. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GnuTLS](https://www.gnutls.org/) - Secure communication library, implementing SSL, TLS and DTLS. [`GNU LGPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [gumbo-parser](https://github.com/google/gumbo-parser) - HTML5 parsing library in C99. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [http-parser](https://github.com/nodejs/http-parser) - HTTP request/response parser. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [ldns](https://www.nlnetlabs.nl/projects/ldns/index.html) - Library to simplify DNS programming. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [libcurl](https://curl.haxx.se/libcurl/) - Client-side URL transfer library, supporting a wide range of formats. [`curl license`](https://curl.haxx.se/docs/copyright.html)
* [LibEtPan](http://www.etpan.org/) - Mail library providing an efficient network for IMAP, SMTP, POP and NNTP. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [libev](http://software.schmorp.de/pkg/libev.html) - Yet another event loop. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [libuv](http://libuv.org/) - Cross-platform asynchronous I/O. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libevent](http://libevent.org/) - Event loop replacement for network servers. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [libgss](https://www.gnu.org/software/gss/) - Generic Security Service. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [libhttpd](https://hughes.com.au/products/libhttpd/) - Library to add basic web server capabilities to an application or embedded device. [`GNU GPL2`](http://www.gnu.org/licenses/gpl-3.0.html)
* [libidn](https://www.gnu.org/software/libidn/) - Implementation of the Stringprep, Punycode and IDNA specifications. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [libmicrohttpd](https://www.gnu.org/software/libmicrohttpd/) - Small C library that makes it easy to run an HTTP server as part of another application. [`GNU LGPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [libsagui](https://risoflora.github.io/libsagui/) - Sagui is a cross-platform C library which helps to develop web servers or frameworks. [`GNU LGPL3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [libvldmail](https://github.com/dertuxmalwieder/libvldmail) - Your friendly e-mail address validation library. [`WTFPLv2`](http://www.wtfpl.net/txt/copying/)
* [lwan](https://lwan.ws/) - Experimental, scalable, high-performance HTTP server. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [mongoose](https://cesanta.com/) - Embedded web server for C. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [MQTT-C](https://github.com/LiamBindle/MQTT-C) - Portable MQTT C client for embedded systems and PCs alike. [`MIT`](https://raw.githubusercontent.com/LiamBindle/MQTT-C/master/LICENSE)
* [nanomsg](https://github.com/nanomsg/nanomsg) - C-based implementation of ZeroMQ. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [OpenSSL](https://www.openssl.org/) - Implementation of the SSL and TLS protocols, and also includes a cryptography library. [`Dual Licensed under the OpenSSL License and the SSLeay License`](https://www.openssl.org/source/license.html)
* [oSip](https://www.gnu.org/software/osip/) - SIP implementation in C without additional dependencies. [`GNU LGPLv2.1 or later`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [pig](https://github.com/rafael-santiago/pig) - Linux packet crafting tool. [`GPL2`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [s2n](https://github.com/awslabs/s2n) - C99 implementation of the TLS/SSL protocols, designed to be simple, fast and with security as a priority. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [socket99](https://github.com/silentbicycle/socket99) - C99 wrapper for the BSD sockets API. [`ISC`](https://directory.fsf.org/wiki/License:ISC)
* [Tox](https://tox.chat/) - Communication platform, designed to be a Skype-killer. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [twitc](https://github.com/sinemetu1/twitc) - Mini C library for interacting with the Twitter OAuth API. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [librg](https://github.com/librg/librg) - Library for building simple and elegant cross-platform mmo client-server solutions. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [dyad](https://github.com/rxi/dyad) - Asynchronous networking library. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [h2o](https://github.com/h2o/h2o/) - Optimized HTTP/1, HTTP/2 high performance server/library. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)

### Web Frameworks ###

* [balde](https://balde.rgm.io/) - Microframework for C based on GLib. [`GNU LGPLv2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [onion](https://www.coralbits.com/libonion/) - C library to create simple HTTP servers and Web Applications. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [kore](https://kore.io/) - Easy to use, scalable and secure web application framework for writing web APIs in C.
* [klone](http://www.koanlogic.com/klone/) - KLone is a fully-featured, multiplatform, web application development framework.
* [duda](http://duda.io/) - Duda I/O is an event-driven and high performant web services framework written in C. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)

## Numerical ##

* [apophenia](http://apophenia.info/) - Library for statistical and scientific computing. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [ATLAS](http://math-atlas.sourceforge.net/) - Automatically Tuned Linear Algebra Software. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [BLAS](http://www.netlib.org/blas/) - Basic Linear Algebra Subprograms; a set of routines that provide vector and matrix operations. [`BLAS license`](http://www.netlib.org/blas/#_licensing)
* [CDFLIB](https://people.sc.fsu.edu/~jburkardt/c_src/cdflib/cdflib.html) - Library with routines to evaluate cumulative density functions fo a variety of standard probability distributions.  Also can compute one parameter of the CDF given the others.  (No license given)
* [cmathl](https://scientificc.github.io/cmathl/) - Pure-C Math library with a great variety of mathematical functions and CMake build support. Seeks to be close to C89/C90 compliant for portability. [`MIT`](https://github.com/ScientificC/cmathl/blob/master/LICENSE)
* [Cuba](http://www.feynarts.de/cuba/) - Library for multidimensional numerical integration. [`GNU LGPLv3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [FFTW](http://www.fftw.org/) - The Fastest Fourier Transform in the West; a highly-optimized fast Fourier transform routine. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [FLINT](http://flintlib.org/) - Fast Library for Number Theory; a library supporting arithmetic with numbers, polynomials, power series and matrices, among others. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [GLPK](https://www.gnu.org/software/glpk/) - GNU Linear Programming Kit; a package designed for solving large-scale linear programming, mixed integer programming and other related problems. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GMP](https://gmplib.org/) - GNU Multple Precision Arithmetic Library; a library for arbitrary-precision arithmetic. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html) and [`GNU LGPLv3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [GNU MPC](http://www.multiprecision.org/mpc/) - Library for complex number arithmetic. [`GNU LGPL3 or later`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [GNU MPFR](https://www.mpfr.org/index.html) - Library for arbitrary-precision floating-point arithmetic. [`GNU LGPL3 or later`](http://www.gnu.org/licenses/lgpl-3.0.html) or [`GNU LGPL2.1 or later (until version 2.4.x)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [GNU MPRIA](https://www.gnu.org/software/mpria/) - Portable mathematics library for multi-precision rational interval arithmetic. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GSL](http://www.gnu.org/software/gsl/) - The GNU Scientific Library; a sophisticated numerical library. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [igraph](https://igraph.org/) - Library for creating and manipulating large graphs. [`GNU GPL2`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [KISS FFT](https://sourceforge.net/projects/kissfft/) - Very simple fast Fourier transform library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [LAPACKE](http://www.netlib.org/lapack/lapacke.html) - C interface to [LAPACK](http://www.netlib.org/lapack/). [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [PARI/GP](http://pari.math.u-bordeaux.fr/) - Computer algebra system for number theory; includes a compiler to C. [`GNU GPL2.1 or later`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [PETSc](https://www.mcs.anl.gov/petsc/) - Suite of data structures and routines for scalable parallel solution of scientific applications modelled by partial differential equations. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [PROB](https://people.sc.fsu.edu/~jburkardt/c_src/prob/prob.html) - Library that handles various discrete and continuous probability density functions.  [`GNU LGPL3`](https://people.sc.fsu.edu/~jburkardt/txt/gnu_lgpl.txt)
* [Yeppp!](https://bitbucket.org/MDukhan/yeppp) - Very fast, SIMD-optimized mathematical library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)

## Parallel Programming ##

* [cchan](http://repo.hu/projects/cchan/) - Small library for channel constructs for inter-thread communication. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [ck](http://concurrencykit.org/) - Concurrency primitives, safe memory reclamation mechanisms and non-blocking data structures. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [mill](http://libmill.org/) - Go-style concurrency in C. [`X11`](https://directory.fsf.org/wiki/License:X11)
* [libdill](http://libdill.org/) - Structured concurrency in C. [`X11`](https://directory.fsf.org/wiki/License:X11)
* [MPICH](http://www.mpich.org/) - Another implementation of MPI. [`MPICH licence`](http://git.mpich.org/mpich.git/blob_plain/6aab201f58d71fc97f2c044d250389ba86ac1e3c:/COPYRIGHT)
* [OpenMP](https://www.openmp.org/) - Set of C pragmas designed to allow for easy parallelization of code. [`3-clause BSD`](https://opensource.org/licenses/BSD-3-Clause)
* [OpenMPI](https://github.com/open-mpi/ompi) - Message passing interface implementation. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [pth](https://www.gnu.org/software/pth/) - Portable implementation for non-preemptive priority-based scheduling for multiple threads of execution. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [pthreads](https://en.wikipedia.org/wiki/POSIX_Threads) - The POSIX thread library.
* [SLEPc](https://bitbucket.org/slepc/slepc) - Software library for the solution of large, sparse eigenvalue problems on parallel computers. [`GNU LGPL3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [TinyCThread](https://tinycthread.github.io/) - Portable, small implementation of the C11 threads API. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)

## Parsers ##

* [hammer](https://github.com/abiggerhammer/hammer) - Parser combinators for binary formats. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [iniparser](https://github.com/ndevilla/iniparser) - Parser for `.ini` files. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libconfini](https://github.com/madmurphy/libconfini) - Yet another INI parser. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [libYAML](https://pyyaml.org/wiki/LibYAML) - YAML 1.1 parser and emitter. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [mpc](https://github.com/orangeduck/mpc) - Parser combinator library. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [libucl](https://github.com/vstakhov/libucl) - Universal configuration library parser. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)


## Regex ##

> "Some people, when confronted with a problem, think 'I know, I'll use regular expressions'. Now they have two problems." - Jamie Zawinski.

* [PCRE](http://www.pcre.org/) - Implementation of regexes identical to that of Perl 5. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [regexp4](https://github.com/nasciiboy/recursiveregexpraptor-4) - Simple and complete implementation of regular expressions with its own sintax. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [SLRE](https://github.com/cesanta/slre) - Super Light Regular Expression library; a very small implementation of a subset of Perl regex syntax. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [sregex](https://github.com/openresty/sregex) - Non-backtracking NFA/DFA-based Perl-compatible regex engine library. [`3-clause BSD`](https://opensource.org/licenses/BSD-3-Clause)
* [TRE](https://github.com/laurikari/tre/) - POSIX-compliant, feature-full regex library. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)

## Serialization ##

* [binn](https://github.com/liteserver/binn) - Binary serialization format meant to be compact, fast and easy-to-use. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [c-capnproto](https://github.com/jmckaskill/c-capnproto) - Implementation of the Cap'n Proto serialization protocol. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [cmp](https://github.com/camgunz/cmp) - Implementation of the [MessagePack](https://msgpack.org/) serialization protocol. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libavro](http://avro.apache.org/docs/current/api/c/index.html#_introduction_to_avro_c) - C implementation of the Avro data serialization system. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [mpack](https://github.com/ludocode/mpack) - Another implementation of the [MessagePack](https://msgpack.org/) serialization protocol. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [netstring-c](https://github.com/liteserver/netstring-c) - Netstring encoder and decoder. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [protobuf-c](https://github.com/protobuf-c/protobuf-c) - Implementation of Google Protocol Buffer in C. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [xdr](https://en.wikipedia.org/wiki/External_Data_Representation) - External Data Representation; a standard for data serialization.

Check also: [JSON](#json), [XML](#xml)

## Source Code Collections ##

This contains collections of small source code. If you want something big and integrated, check the Frameworks section.

* [CCAN](http://ccodearchive.net/) - Modelled after Perl's CPAN, this is a big collection of C code that does stuff. The full list is [here](http://ccodearchive.net/list.html).
* [clib](https://github.com/clibs/clib) - Something of a package manager for C. Comes with a [bunch of libraries of its own](https://github.com/clibs/clib/wiki/Packages). [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [gnulib](https://www.gnu.org/software/gnulib/) - Collection of common GNU code.
* [libdjb](http://www.fefe.de/djb/) - Collection of libraries doing various things. [`(Apparently) Public Domain`](https://creativecommons.org/share-your-work/public-domain/)

## Standard Libraries ##

This contains standard C libraries.

* [Bionic](https://github.com/aosp-mirror/platform_bionic) - Google's C standard library, developed for Android. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [dietlibc](http://www.fefe.de/dietlibc/) - C standard library designed for the smallest possible binaries. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [glibc](http://www.gnu.org/software/libc/) - The GNU C Library; an implementation of the C standard library. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [musl](http://www.musl-libc.org/) - Standard C library, compatible with POSIX 2008 and C11. Designed for static linking. [`Expat`](https://directory.fsf.org/wiki/License:Expat)

## String Manipulation ##

* [bstrlib](http://bstring.sourceforge.net/) - The Better String Library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause) and [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [ICU](http://site.icu-project.org/) - International Components for Unicode; a library for Unicode support. [`ICU license`](http://source.icu-project.org/repos/icu/icu/tags/latest/LICENSE)
* [libunistring](https://www.gnu.org/software/libunistring/) - Library for manipulating Unicode strings in C. [`GNU LGPL3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [libgiconv](https://www.gnu.org/software/libiconv/) - Text conversion library. [`GNU LGPL2.1 (library)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`GNU GPL3 (*iconv* program)`](http://www.gnu.org/licenses/gpl-3.0.html)
* [SDS](https://github.com/antirez/sds) - Simple Dynamic Strings; a library for handling C strings in a simpler way, but one that is compatible with normal C string functions. Available via [clib](https://github.com/clibs/clib). [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [shoco](http://ed-von-schleck.github.io/shoco/) - Compressor for small text strings. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [smaz](https://github.com/antirez/smaz) - Efficient string compression library. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [utf8.h](https://github.com/sheredom/utf8.h) - Single header utf8 string functions. [`Unlicense`](https://unlicense.org/)
* [utf8proc](https://github.com/JuliaStrings/utf8proc) - Small, clean library for processing UTF-8 Unicode data. [`License`](https://github.com/JuliaStrings/utf8proc/blob/master/LICENSE.md)

## Testing ##

* [CHEAT](http://users.jyu.fi/~sapekiis/cheat/) - Very simple unit testing framework. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [Check](https://libcheck.github.io/check/) - Unit testing framework for C. [`GNU LGPL2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [CMock](http://www.throwtheswitch.org/) - Mock/stub generator for C. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [cmocka](https://cmocka.org/) - Unit testing framework with support for mock objects. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [Criterion](https://criterion.readthedocs.io/en/master/) - KISS, non-intrusive C test framework. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [CUnit](http://cunit.sourceforge.net/) - Another unit testing framework for C. [`GNU LGPL2.0`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [Cutest](https://github.com/rafael-santiago/cutest) - Library for unit testing with memory leak detection (Linux, freeBSD and Windows). [`GPL2`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [minunit](https://github.com/siu/minunit) - Minimal unit testing framework for C. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [munit](https://nemequ.github.io/munit/) - Small but full-featured unit testing framework for C with no dependencies. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [Unity](http://www.throwtheswitch.org/) - Simple unit testing framework for C. [`Expat`](https://directory.fsf.org/wiki/License:Expat)

## Text Editor Extensions ##

While practically any decent programmer's text editor supports C, there are some extensions that make it more pleasant. This is categorized by editor.

### Atom ###
* [linter-clang](https://github.com/AtomLinter/linter-clang) - Lint C code in Atom, using Clang. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)
* [linter-gcc](https://github.com/hebaishi/linter-gcc) - Lint C code in Atom, using GCC. [`MIT`](https://raw.githubusercontent.com/atom/atom/master/LICENSE.md)

### Emacs ###

* [CEDET](http://cedet.sourceforge.net/) - Collection of Emacs Development Environment Tools; designed to provide IDE-like features to Emacs. Built-in. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Flycheck](https://github.com/flycheck/flycheck) - Modern syntax checking. For C, it can use either GCC or Clang as a back-end. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Yasnippet](https://github.com/joaotavora/yasnippet) - Template system, with C templates for common code snippets. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)

### Vim ###

* [Syntastic](https://github.com/vim-syntastic/syntastic) - Syntax checking and linting. [`Do What The Fuck You Want To license`](https://github.com/vim-syntastic/syntastic/blob/master/LICENCE)
* [YouCompleteMe](http://valloric.github.io/YouCompleteMe/) - Code completion engine for Vim. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)

## Tools ##

This is a list of useful programs to help you write and debug C code which are *not* editors, libraries or compilers.

* [Artistic Style](http://astyle.sourceforge.net/) - Fast and small automatic source code formatter that supports C. [`GNU LGPL3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [address-sanitizer](https://github.com/google/sanitizers) - Fast memory error detector. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [biicode](https://biicode.github.io/biicode/) - Modern dependency manager for C. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [c](https://github.com/ryanmjacobs/c) - Compile and execute C "scripts" in one go on the command line. Also has shebang support. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [c99sh](https://github.com/RhysU/c99sh) - Run C files using hash-bang. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [CBMC](http://www.cprover.org/cbmc/) - C Bounded Model Checker; a tool for verification of array bounds, pointer safety and user-specified assertions. [`Original BSD`](https://directory.fsf.org/wiki/License:BSD-4-Clause)
* [cdecl](https://cdecl.org/) - Online service to translate C declarations into English and vice versa. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [cinclude2dot](https://www.flourish.org/cinclude2dot/) - Graphs include dependencies in a C project using Graphviz. [`Any GNU GPL version (due to underspecification in the file)`](https://directory.fsf.org/wiki/Cinclude2dot#tab=Details)
* [Complexity](https://www.gnu.org/software/complexity/) - Tool for measuring the complexity of C source code. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [CScout](https://www.spinellis.gr/cscout/) - Source code analyzer and refactoring browser for collections of C programs. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [DDD](https://www.gnu.org/software/ddd/ddd.html) - Graphical front-end for a range of command-line debuggers. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GDB](http://www.gnu.org/software/gdb/) - The GNU Project debugger; a debugger for C. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Glade](https://glade.gnome.org/) - RAD tool to enable quick development of GTK+ GUIs. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [GMSL](https://gmsl.sourceforge.io/) - GNU Make Standard Library; a collection of additional functionality for GNU Make. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [GNU Global](https://www.gnu.org/software/global/) - Source code tagging tool which works with C. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [gprof](http://www.gnu.org/software/binutils/) - Performance analysis tool. Part of GNU binutils. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [Highlight](http://www.andre-simon.de/index.php) - Converts source code to formatted text with nice highlighting. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [include-what-you-use](https://github.com/include-what-you-use/include-what-you-use) - Helps find unecessary inclusions and make suggestions for fixing them. Based on LLVM/Clang (and only works with it). [`NCSA`](https://directory.fsf.org/wiki/License:NCSA)
* [indent](https://www.gnu.org/software/indent/) - Formats C source code automatically to make it easier to read. Also converts from one style of source to another. [`GNU GPLv3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [rr](https://rr-project.org/) - Debugger that records non-deterministic executions to allow for deterministic debugging. [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [tup](http://gittup.org/tup/index.html) - Very fast, file-based, cross-platform build system. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [unifdef](http://dotat.at/prog/unifdef/) - Removes #ifdef and #if directives with their delimited text without touching any other part of the file. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause) and [`FreeBSD`](https://directory.fsf.org/wiki?title=License:FreeBSD)
* [Valgrind](http://www.valgrind.org/) - Range of dynamic analysis tools, including a leak checker. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)

## Utilities ##

This is a 'catch-all' category for anything that doesn't fit well anywhere else.

* [ApeTagLibs](https://github.com/jeremyevans/ape_tag_libs/tree/master/c) - C library for working with APEv2 tags. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [bfd](http://sourceware.org/binutils/docs/bfd/) - Library for manipulating binary object files. Part of GNU binutils. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [cf4ocl](https://fakenmc.github.io/cf4ocl/) - The C Framework for OpenCL; a cross-platform object-oriented framework for developing and benchmarking  [OpenCL](https://www.khronos.org/opencl/) projects. [`GNU LGPL3 (library)`](http://www.gnu.org/licenses/lgpl-3.0.html) or [`GNU GPL3 (project code)`](http://www.gnu.org/licenses/gpl-3.0.html)
* [CommonMark](https://github.com/commonmark/commonmark-spec) - C implementation of the CommonMark spec. [`Various Licenses`](https://github.com/commonmark/commonmark-spec/blob/master/LICENSE)
* [CException](https://github.com/ThrowTheSwitch/CException) - C implementation of exceptions. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [docopt.c](https://github.com/docopt/docopt.c) - C implementation of a command-line option parser. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [dyncall](http://www.dyncall.org/) - Another foreign function interface library. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [FANN](http://leenissen.dk/fann/wp/) - Fast Artifical Neural Network library; an implementation of neural networks. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Firm](https://pp.ipd.kit.edu/firm/) - C library that provides a graph-based intermediate representation, optimizations and assembly code generation suitable for use in compilers. Comes with an example C front-end under the same license. [`GNU LGPLv2.1`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
* [Genann](https://github.com/codeplea/genann) - Simple neural network library in C. [`Zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [gjrand](https://sourceforge.net/projects/gjrand/) - Library of random-number generation routines. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html) or [`GNU GPLv3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GNU FreeIPMI](https://www.gnu.org/software/freeipmi/index.html) - In-band and out-of-band IPMI implementation. [`GNU GPL3`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GNU gperf](https://www.gnu.org/software/gperf/) - Perfect hash function generator, given a list of strings. Outputs C code. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [GNU Libffcall](https://www.gnu.org/software/libffcall/) - Collection of libraries for building foreign function interfaces. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [gperftools](https://github.com/gperftools/gperftools) - Collection of utilities for measuring and improving performance. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [huffandpuff](https://github.com/adamierymenko/huffandpuff) - Minimal Huffman encoder and decoder. [`Public Domain`](https://creativecommons.org/share-your-work/public-domain/)
* [kdtree](https://github.com/jtsiomb/kdtree) - Simple library for working with KD-trees. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [Kitsune](http://kitsune-dsu.com/) - Efficient, general-purpose framework for dynamic software updating. [`GNU LGPL3 or later`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [libavl](http://adtinfo.org/libavl.html/index.html) - Library containing a range of self-balancing binary trees. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [libbson](https://github.com/mongodb/libbson) - BSON utility library. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [libCello](http://libcello.org/) - Library introducing higher-level programming to C. [`3-clause BSD`](https://directory.fsf.org/wiki/License:BSD-3-Clause)
* [libffi](https://github.com/libffi/libffi) - Portable foreign-function interface library. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libgit2](https://libgit2.org/) - Pure C implementation of Git. [`GNU GPL2 only, with a linking exception`](https://github.com/libgit2/libgit2/blob/master/COPYING)
* [libimobiledevice](https://github.com/libimobiledevice/libimobiledevice) - Cross-platform protocol library to communicate with iThings. [`GNU LGPLv2.1 or later (library)`](http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) or [`GNU GPL2.1 or later (tools)`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [libnfc](https://github.com/nfc-tools/libnfc) - Platform-independent Near-Field Communication library. [`GNU LGPL3`](http://www.gnu.org/licenses/lgpl-3.0.html)
* [libPhenom](https://github.com/facebookarchive/libphenom) - Deprecated, here for archival purposes. Eventing framework for building high-scalability and high-performance systems. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [ncurses](https://www.gnu.org/software/ncurses/) - Coloured terminal UI library. [`GNU GPL3 or later`](http://www.gnu.org/licenses/gpl-3.0.html)
* [nope.c](https://github.com/riolet/WAFer) - C-language-based, ultra-light software platform for scalable server-side and networking applications (think node.js for C programmers). [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [pbc](https://github.com/cloudwu/pbc) - Protocol buffers library. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [rabbitmq-c](https://github.com/alanxz/rabbitmq-c) - Client library for [RabbitMQ](https://www.rabbitmq.com/). [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [Ragel](http://www.colm.net/open-source/ragel/) - DSL for state machines that compiles to C. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [Tinyexpr](https://github.com/codeplea/tinyexpr) - Tiny recursive-descent parser, compiler and evaluation engine for simple mathematical expressions. [`zlib`](https://directory.fsf.org/wiki/License:Zlib)
* [uthash](http://troydhanson.github.io/uthash/) - Hash table implementation, allowing existing structures to be stored in a hash table easily. [`1-clause BSD`](http://troydhanson.github.io/uthash/license.html)
* [cpu_features](https://github.com/google/cpu_features) - A cross platform C99 library to get cpu features at runtime. [`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [pblog](https://github.com/google/pblog) - Small, low overhead, structured logging library intended for logging formware events.[`Apache 2.0`](https://directory.fsf.org/wiki/License:Apache-2.0)
* [libelf](https://github.com/WolfgangSt/libelf) - ELF object file access library in C. [`GNU GPL2.1`](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
* [mcpp](http://mcpp.sourceforge.net/) - Portable C preprocessor. [`2-clause BSD`](https://opensource.org/licenses/BSD-2-Clause)
* [libusb](https://libusb.info/) - Generic access to USB devices. [`LGPL2.1`](https://github.com/libusb/libusb/blob/master/COPYING)
* [alsa-lib](https://www.alsa-project.org/main/index.php/Main_Page ) - Userspace library to interact with ALSA. [`LGPL2.1`](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html)
* [Capstone](https://github.com/aquynh/capstone) - Dissasembly/disassembler framework. [`BSD 3-clause`](https://github.com/aquynh/capstone/blob/master/LICENSE.TXT)

## XML ##

> "XML is crap. Really. There are no excuses. XML is nasty to parse for humans, and it's a disaster to parse even for computers. There's just no reason for that horrible crap to exist." - Linus Torvalds

* [Expat](http://www.libexpat.org/) - Stream-oriented XML parser. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [libxml2](http://xmlsoft.org/) - Standards-compliant, portable XML parser. [`Expat`](https://directory.fsf.org/wiki/License:Expat)
* [mini-xml](https://github.com/michaelrsweet/mxml) - Small XML reading and writing library. No dependencies aside from C standard library. [`Apache 2.0 with exceptions`](https://github.com/michaelrsweet/mxml/blob/master/LICENSE)
