Build Systems

• aimake - Build tool designed to avoid complex configurations. GNU GPL3 or later

• Autoconf - Extensible package of M4 macros that produce shell scripts to automatically configure software source code packages. Part of the Autotools. GNU GPL3 or later

• Automake - 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

• Libtool - Generic library support script. Part of the Autotools. GNU GPL3 or later

Compilers

• GCC - Provides a C compiler as part of its compiler set. Supports C11 and OpenMP. GNU GPL3 or later

Database

• BerkeleyDB - Library for a high-performance embedded database for key-value data. GNU AGPLv3

• recutils - Set of tools and a C library for accessing human-editable, plaintext database files called recfiles. GNU GPL3 or later

Editors

• Code::Blocks - Extensible, configurable IDE supporting C. GNU GPL3

Engines

• Spearmint - Engine designed for FPS games. GNU GPL3 or later

Resources

• RetroArch - The reference frontend for libretro. GNU GPL3

Graphics

• libxmi - Function library for rasterizing 2D vector graphics. GNU GPL3 or later

Memory Allocators / Language Standards

• Hoard - A Fast, Scalable, and Memory-efficient Malloc for Linux, Windows, Mac, and Solaris. GNU GPL2

• nedmalloc - An EXTREMELY FAST portable thread caching malloc(3) implementation written in C. GNU GPL2

Networking and Internet / Language Standards

• GNU adns - Advanced, easy-to-use, asynch-capable DNS client library and utilities. GNU GPL3 or later

• GNU SASL - Implementation of the Simple Authentication and Security Layer and a few common SASL mechanism. GNU GPL3 or later

• libgss - Generic Security Service. GNU GPL3 or later

• libhttpd - Library to add basic web server capabilities to an application or embedded device. GNU GPL2

• libidn - Implementation of the Stringprep, Punycode and IDNA specifications. GNU GPL3 or later

• libsagui - Sagui is a cross-platform C library which helps to develop web servers or frameworks. GNU LGPL3

• Tox - Communication platform, designed to be a Skype-killer. GNU GPL3

Numerical / Language Standards

• Cuba - Library for multidimensional numerical integration. GNU LGPLv3

• 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

• GMP - GNU Multple Precision Arithmetic Library; a library for arbitrary-precision arithmetic. GNU GPL2.1 and GNU LGPLv3

• GNU MPC - Library for complex number arithmetic. GNU LGPL3 or later

• GNU MPFR - Library for arbitrary-precision floating-point arithmetic. GNU LGPL3 or later or GNU LGPL2.1 or later (until version 2.4.x)

• GNU MPRIA - Portable mathematics library for multi-precision rational interval arithmetic. GNU GPL3 or later

• GSL - The GNU Scientific Library; a sophisticated numerical library. GNU GPL3

Parallel Programming / Language Standards

• pth - Portable implementation for non-preemptive priority-based scheduling for multiple threads of execution. GNU GPL3 or later

• SLEPc - Software library for the solution of large, sparse eigenvalue problems on parallel computers. GNU LGPL3

Parsers / Language Standards

• libconfini (⭐100) - Yet another INI parser. GNU GPL3 or later

Regex / Language Standards

• regexp4 (⭐8) - Simple and complete implementation of regular expressions with its own sintax. GNU GPL3 or later

String Manipulation / Language Standards

• libunistring - Library for manipulating Unicode strings in C. GNU LGPL3

• libgiconv - Text conversion library. GNU LGPL2.1 (library) or GNU GPL3 (*iconv* program)

Emacs / Language Standards

• CEDET - Collection of Emacs Development Environment Tools; designed to provide IDE-like features to Emacs. Built-in. GNU GPL3 or later

• Flycheck (⭐2.2k) - Modern syntax checking. For C, it can use either GCC or Clang as a back-end. GNU GPL3 or later

• Yasnippet (⭐2.5k) - Template system, with C templates for common code snippets. GNU GPL3 or later

Vim / Language Standards

• YouCompleteMe - Code completion engine for Vim. GNU GPL3

Tools / Language Standards

• Artistic Style - Fast and small automatic source code formatter that supports C. GNU LGPL3

• Complexity - Tool for measuring the complexity of C source code. GNU GPL3 or later

• CScout - Source code analyzer and refactoring browser for collections of C programs. GNU GPL3

• DDD - Graphical front-end for a range of command-line debuggers. GNU GPL3 or later

• GDB - The GNU Project debugger; a debugger for C. GNU GPL3 or later

• GNU Global - Source code tagging tool which works with C. GNU GPL3

• gprof - Performance analysis tool. Part of GNU binutils. GNU GPL3 or later

• Highlight - Converts source code to formatted text with nice highlighting. GNU GPL3

• 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

Utilities / Language Standards

• bfd - Library for manipulating binary object files. Part of GNU binutils. GNU GPL3 or later

• cf4ocl - The C Framework for OpenCL; a cross-platform object-oriented framework for developing and benchmarking OpenCL projects. GNU LGPL3 (library) or GNU GPL3 (project code)

• gjrand - Library of random-number generation routines. GNU GPL2.1 or GNU GPLv3

• GNU FreeIPMI - In-band and out-of-band IPMI implementation. GNU GPL3

• GNU gperf - Perfect hash function generator, given a list of strings. Outputs C code. GNU GPL3 or later

• GNU Libffcall - Collection of libraries for building foreign function interfaces. GNU GPL3 or later

• Kitsune - Efficient, general-purpose framework for dynamic software updating. GNU LGPL3 or later

• libavl - Library containing a range of self-balancing binary trees. GNU GPL3 or later

• libnfc (⭐1.3k) - Platform-independent Near-Field Communication library. GNU LGPL3

• ncurses - Coloured terminal UI library. GNU GPL3 or later

Build Systems

• Meson - Extremely fast, user-friendly build system. Based on Ninja. Apache 2.0

• Buck - Build system created and used by Facebook. Apache 2.0

Compilers

• ccache - Compiler cache designed to speedup recompilation. GNU GPL3 or later

Frameworks

• C Macro Collections (⭐324) - Header only, macro generated, generic and type-safe Collections in C. MIT

Utilities / Language Standards

• CommonMark (⭐4.7k) - C implementation of the CommonMark spec. Various Licenses

Build Systems

• Qbs - Modern build tool for software projects. LGPL3

• xmake - Cross-platform build utility based on lua. Apache 2.0

Hashing

• t1ha (⭐333) - Fast Positive Hash library. zlib

Beginner / Language Standards

• Tutorial on pointers

Intermediate / Language Standards

• What a C programmer should know about memory

Self-study courses / Language Standards

• C Programming Language Certified Associate preparation course

String Manipulation / Language Standards

• utf8.h (⭐1.3k) - Single header utf8 string functions. Unlicense

Utilities / Language Standards

• libPhenom (⭐1.7k) - Deprecated, here for archival purposes. Eventing framework for building high-scalability and high-performance systems. Apache 2.0

• rabbitmq-c (⭐1.6k) - Client library for RabbitMQ. Expat

• alsa-lib - Userspace library to interact with ALSA. LGPL2.1

XML / Language Standards

• mini-xml (⭐360) - Small XML reading and writing library. No dependencies aside from C standard library. Apache 2.0 with exceptions

Resources

• raylib - Simple and easy-to-use library to learn videogames programming. zlib

Memory Allocators / Language Standards

• rpmalloc (⭐1.6k) - Cross platform, lock-free memory allocator. Public Domain

Regex / Language Standards

• sregex (⭐598) - Non-backtracking NFA/DFA-based Perl-compatible regex engine library. 3-clause BSD

String Manipulation / Language Standards

• utf8proc (⭐828) - Small, clean library for processing UTF-8 Unicode data. License

Documentation Generation

• Doxygen - The de-facto standard tool for generating C documentation from annotated sources. Can generate a large range of formats. GNU GPL2.1

Resources

• GLFW - Multi-platform library for creating windows with OpenGL contexts. zlib

Networking and Internet / Language Standards

• MQTT-C (⭐544) - Portable MQTT C client for embedded systems and PCs alike. MIT

Numerical / Language Standards

• igraph - Library for creating and manipulating large graphs. GNU GPL2

Compression

• pixz (⭐609) - Pixz (pronounced pixie) is a parallel, indexing version of xz. 2-clause BSD

Numerical / Language Standards

• CDFLIB - 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)

• PROB - Library that handles various discrete and continuous probability density functions. GNU LGPL3

Testing / Language Standards

• Check - Unit testing framework for C. GNU LGPL2.1

Graphical User Interface

• LCUI (⭐3.8k) - Small C library for building user interfaces with C, XML and CSS. MIT

Networking and Internet / Language Standards

• h2o (⭐10k) - Optimized HTTP/1, HTTP/2 high performance server/library. MIT

Numerical / Language Standards

• 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

• PETSc - Suite of data structures and routines for scalable parallel solution of scientific applications modelled by partial differential equations. FreeBSD

RTOS

• RIOT OS - Real-time multi-threading operating system that supports a range of devices that are typically found in the Internet of Things. LGPL-2.1

Build Systems

• Premake (⭐2.5k) - Build script generator for toolsets like Visual Studio, Xcode, or GNU Make. 3-clause BSD

• SCons - An easier, more reliable and faster way to build software. MIT

• Ninja (⭐8.6k) - Small, simple build system with a focus on speed. Apache 2.0

• Bazel - Build system for various operating systems and targets. Apache 2.0

Compilers

• Clang - C compiler for LLVM. Supports C11. NCSA

Compiler libraries

• yasm - Yasm Modular Assembler Project. 2-clause BSD

Compression

• libzip - A C library for reading, creating, and modifying zip archives. 3-clause BSD

• zlib - Massively-spiffy yet delicately-unobtrusive compression library. 3-clause BSD

• bzip2 - Patent free, high quality data compressor. 3-clause BSD

• zstd - Fast real-time compression algorithm 3-clause BSD

Crypto

• mbed TLS - Another crypto implementation for C. Apache 2.0

Database

• Hiredis (⭐5.5k) - Minimalistic client library for Redis. 3-clause BSD

• LMDB (⭐2.1k) - Ultra-fast, ultra-compact key-value embedded data store. OpenLDAP License

• MariaDB - Robust, scalable and reliable SQL server, designed to be a drop-in replacement for MySQL. 3-clause BSD

• mongo-c-driver - High-performance client library for MongoDB. Apache 2.0

• Redis - Advanced key-value store. 3-clause BSD

• SQLite - Self-contained, serverless, zero-configuration, transactional SQL database engine with a C interface. Public Domain

Documentation Generation

• DocOnce - Modestly-tagged markup language that can be used to generate a range of formats. 3-clause BSD

Editors

• Eclipse - IDE written in Java. EPL

RTOS

• Zephyr Project - Scalable real-time RTOS supporting multiple hardware architectures, optimized for resource constrained devices. Apache 2.0

Frameworks

• APR - Apache Portable Runtime; another library of cross-platform utility functions. Apache 2.0

• libU - Small library of basic utilities, including memory allocation, string manipulation and logging. 3-clause BSD

• libsrt - Safe Real-Time library for C. 3-clause BSD

Resources

• Allegro - Cross-platform, video game development and multimedia library. zlib

Graphics

• Cairo -2D graphics library. GNU LGPL2.1 or MPLv1.1

• mozjpeg (⭐5k) - Improved JPEG encoder. 3-clause BSD

Hashing

• jwHash (⭐212) - Fast hashtable implementation. Apache 2.0

• xxHash - Extremely fast non-cryptographic hash algorithm. 2-clause BSD

Image Processing

• libccv - Modern Computer Vision Library. 3-clause BSD

Multimedia / Language Standards

• lodepng - Simple PNG image decoder and encoder, requiring no other dependencies. 3-clause BSD

Networking and Internet / Language Standards

• gumbo-parser (⭐5.1k) - HTML5 parsing library in C99. Apache 2.0

• ldns - Library to simplify DNS programming. 3-clause BSD

• LibEtPan - Mail library providing an efficient network for IMAP, SMTP, POP and NNTP. 3-clause BSD

• libevent - Event loop replacement for network servers. 3-clause BSD

• s2n (⭐4.2k) - C99 implementation of the TLS/SSL protocols, designed to be simple, fast and with security as a priority. Apache 2.0

• librg (⭐1k) - Library for building simple and elegant cross-platform mmo client-server solutions. Apache 2.0

Web Frameworks / Language Standards

• onion - C library to create simple HTTP servers and Web Applications. Apache 2.0

• duda - Duda I/O is an event-driven and high performant web services framework written in C. Apache 2.0

Numerical / Language Standards

• ATLAS - Automatically Tuned Linear Algebra Software. 3-clause BSD

• KISS FFT - Very simple fast Fourier transform library. 3-clause BSD

• LAPACKE - C interface to LAPACK. 3-clause BSD

• Yeppp! - Very fast, SIMD-optimized mathematical library. 3-clause BSD

Parallel Programming / Language Standards

• OpenMP - Set of C pragmas designed to allow for easy parallelization of code. 3-clause BSD

• OpenMPI (⭐1.6k) - Message passing interface implementation. 3-clause BSD

Parsers / Language Standards

• libYAML - YAML 1.1 parser and emitter. Expat

Regex / Language Standards

• PCRE - Implementation of regexes identical to that of Perl 5. 3-clause BSD

Serialization / Language Standards

• binn (⭐378) - Binary serialization format meant to be compact, fast and easy-to-use. Apache 2.0

• libavro - C implementation of the Avro data serialization system. Apache 2.0

Standard Libraries / Language Standards

• Bionic (⭐555) - Google's C standard library, developed for Android. 3-clause BSD

String Manipulation / Language Standards

• bstrlib - The Better String Library. 3-clause BSD and GNU GPL2.1

• smaz (⭐1k) - Efficient string compression library. 3-clause BSD

Testing / Language Standards

• cmocka - Unit testing framework with support for mock objects. Apache 2.0

• Criterion - KISS, non-intrusive C test framework. Expat

Tools / Language Standards

• address-sanitizer (⭐8.8k) - Fast memory error detector. Apache 2.0

• CBMC - C Bounded Model Checker; a tool for verification of array bounds, pointer safety and user-specified assertions. Original BSD

• GMSL - GNU Make Standard Library; a collection of additional functionality for GNU Make. 3-clause BSD

• include-what-you-use (⭐3k) - Helps find unecessary inclusions and make suggestions for fixing them. Based on LLVM/Clang (and only works with it). NCSA

• unifdef - Removes #ifdef and #if directives with their delimited text without touching any other part of the file. 3-clause BSD and FreeBSD

Utilities / Language Standards

• Genann (⭐1.3k) - Simple neural network library in C. Zlib

• gperftools (⭐7.2k) - Collection of utilities for measuring and improving performance. 3-clause BSD

• kdtree (⭐345) - Simple library for working with KD-trees. 3-clause BSD

• libbson (⭐342) - BSON utility library. Apache 2.0

• libCello - Library introducing higher-level programming to C. 3-clause BSD

• libgit2 - Pure C implementation of Git. GNU GPL2 only, with a linking exception

• Tinyexpr (⭐1.2k) - Tiny recursive-descent parser, compiler and evaluation engine for simple mathematical expressions. zlib

• cpu_features (⭐2.1k) - A cross platform C99 library to get cpu features at runtime. Apache 2.0

• pblog (⭐24) - Small, low overhead, structured logging library intended for logging formware events.Apache 2.0

Compilers

• CompCert - Fully-verified C compiler. Supports almost all of C89. GNU GPL2.1 or later

• Intel SPMD - Compiler for a variant of the C language, for single program, multiple data programming. Various licenses

Compression

• lz4 - Fast Compression algorithm.

• quicklz - Fast compression library. GNU GPL2.1

Crypto

• libgcrypt - General-purpose cryptography library, with a range of available ciphers. GNU LGPL2.1or later (code) and GNU GPL2.1 or later (manual and tools)

• libsodium - Modern and easy-to-use crypto library. Expat

• libtomcrypt - Fairly comprehensive, modular and portable cryptographic toolkit. Public Domain

Database

• sophia - Modern, embeddable key-value database. FreeBSD

Editors

• Qt Creator - Cross-platform IDE written with C++ and Qt, part of the Qt SDK. Supports Clang Code Model. GNU GPL3 with Qt exception

RTOS

• Amazon FreeRTOS - RTOS for microcontrollers that makes small, low-power edge devices easy to program. MIT

• Contiki - Connect low-cost, low power microcontrollers to the Internet. 3-clause BSD

Frameworks

• C Algorithms - Collection of common algorithms and data structures for C. ISC

• EFL - Large collection of useful data structures and functions.

• qlibc - Simple and powerful C library, designed as a replacement for GLib while focusing on being small and light. qLib license (similar to FreeBSD)

Engines

• ioquake3 - The Quake3 engine, freed at last. GNU GPL2.1

• Orx - Portable, lightweight, plugin-based, data-driven, 2D-oriented game engine. zlib

Resources

• Chipmunk2D - Fast and lightweight 2D game physics library. Expat

• FreeGLUT - Alternative to the OpenGL Utility Toolkit. Allows the creation and management of windows with OpenGL contexts. X11

• libao - Cross-platform audio library with a wide variety of outputs. GNU GPL2.1 or later

• SDL and SDL2 - 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

Generic Programming

• klib - Small and lightweight implementations of common algorithms and data structures. MIT

JSON

• WJElement (⭐101) - Advanced JSON manipulation library, with support for JSON Schema. LGPL, any version

Memory Allocators / Language Standards

• jemalloc - General purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support, commonly used in production systems. FreeBSD

Multimedia / Language Standards

• libmpv - Music-playing library. Compile with ./waf configure --disable-cplayer --enable-libmpv-shared to not have the music player. GNU GPL2.1 or later

• libsoundio - Library for cross-platform, real-time audio input and output. Has a range of back-ends. Expat

Networking and Internet / Language Standards

• czmq - High-level binding for ZeroMQ. MPL2.0

• libuv - Cross-platform asynchronous I/O. Expat

• lwan - Experimental, scalable, high-performance HTTP server. GNU GPL2.1

• mongoose - Embedded web server for C. GNU GPL2.1

Web Frameworks / Language Standards

• balde - Microframework for C based on GLib. GNU LGPLv2.1

• kore - Easy to use, scalable and secure web application framework for writing web APIs in C.

• klone - KLone is a fully-featured, multiplatform, web application development framework.

Numerical / Language Standards

• apophenia - Library for statistical and scientific computing. GNU GPL2.1

Parallel Programming / Language Standards

• ck - Concurrency primitives, safe memory reclamation mechanisms and non-blocking data structures. FreeBSD

• libdill - Structured concurrency in C. X11

String Manipulation / Language Standards

• shoco - Compressor for small text strings. Expat

Testing / Language Standards

• CHEAT - Very simple unit testing framework. FreeBSD

• CMock - Mock/stub generator for C. Expat

• Unity - Simple unit testing framework for C. Expat

Tools / Language Standards

• rr - Debugger that records non-deterministic executions to allow for deterministic debugging. FreeBSD

Utilities / Language Standards

• libusb - Generic access to USB devices. LGPL2.1

Build Systems

• CMake - Tools for cross-platform building, testing, and packaging. 3-clause BSD

• Jam - Build system, designed to be easier than make. Understands C build rules implicitly. Jam License

• qmake - Build system included with the Qt Framework. GNU GPL3 with Qt Exception

Compilers

• PCC - Venerable C compiler. Supports C99. Various free licenses

• TCC - Tiny C Compiler; a small, fast C compiler. Supports C99 (except complex types). GNU LGPL2.1

Compression

• lzo - Very fast data compression library. GNU GPL2.1

• snappy (⭐5.4k) - Fast compression library (implementation in C++, native bindings to C).

• brotli (⭐12k) - Generic lossless compression algorithm based on LZ77, Huffman coding and 2nd order context modelling MIT

Networking and Internet / Language Standards

• GnuTLS - Secure communication library, implementing SSL, TLS and DTLS. GNU LGPL2.1 or later

• OpenSSL - Implementation of the SSL and TLS protocols, and also includes a cryptography library. Dual Licensed under the OpenSSL License and the SSLeay License

• asnlc - Compiler of ASN.1 specifications into C source code. FreeBSD

• http-parser (⭐6.1k) - HTTP request/response parser. Expat

• libcurl - Client-side URL transfer library, supporting a wide range of formats. curl license

• libev - Yet another event loop. FreeBSD

• libmicrohttpd - Small C library that makes it easy to run an HTTP server as part of another application. GNU LGPL2.1 or later

• libvldmail (⭐47) - Your friendly e-mail address validation library. WTFPLv2

• nanomsg (⭐5.5k) - C-based implementation of ZeroMQ. Expat

• oSip - SIP implementation in C without additional dependencies. GNU LGPLv2.1 or later

• pig (⭐426) - Linux packet crafting tool. GPL2

• socket99 (⭐134) - C99 wrapper for the BSD sockets API. ISC

• twitc (⭐25) - Mini C library for interacting with the Twitter OAuth API. Expat

• dyad (⭐1.4k) - Asynchronous networking library. MIT

Crypto

• libressl - Modernized fork of OpenSSL. Various Licenses

Database

• PostgreSQL - Powerful object-relational database system. PostgreSQL licence

• UnQLite - Self-contained, serverless, zero-configuration, transactional NoSQL engine with a C interface. FreeBSD

Documentation Generation

• Cxref - Generates documentation of C programs in either LaTeX, HTML, RTF or SGML. GNU GPL2.1

• GTK-Doc - Tool for generating C documentation from annotated sources. Has support for the Autotools. GNU GPL2.1 (code) or GNU FDL1.1

Editors

• Anjuta DevStudio - The GNOME IDE. GNU GPL2.1

• Atom - Hackable text editor for the 21st century. MIT

• CodeLite - Cross-platform IDE. GNU GPL2.1

• Geany - Very small and fast IDE. GNU GPL2.1 or later

• KDevelop - The KDE IDE. GNU GPL2.1

RTOS

• ChibiOS - RTOS with complete development environment (HAL, drivers, support files, and tools). Various Licenses

Environments

• Cygwin - Designed to emulate a POSIX-compatible environment extensively under Windows. Various Licenses

• MinGW-w64 - Minimalist environment for C development on Windows with 64 bit support. Various Licenses

Frameworks

• CPL - The Common Pipeline Library; a set of libraries designed to be a comprehensive, efficient and robust software toolkit. GNU GPL2.1

• GLib - Library of utility functions and structures, designed to be portable, efficient and powerful. GNU LGPL2.1

• GIO - Modern and easy-to-use VFS API. GNU LGPL2.1

• GObject - Object-oriented system and object model for C. GNU LGPL2.1

• libnih (⭐80) - Lightweight library of C functions and structures. GNU GPL2.1

• PBL - Large library of utilities, featuring data structures, among other things. GNU LGPL2.1 or later (library) or GNU GPL2.1 or later (test code)

• stb (⭐20k) - Range of single-file libraries for C. Public Domain

Engines

• Corange (⭐1.6k) - Game engine in pure C. FreeBSD

• Darkplaces - Modified version of the Quake2 engine. GNU GPL2.1

• Quake (⭐3.8k) - The Quake engine. GNU GPL2.1

• Quake2 (⭐2.2k) - The Quake2 engine. GNU GPL2.1

Resources

• CSFML - Binding for SFML in C. zlib

Graphics

• Cogl (⭐0) - GPU graphics and utilities API. Expat

• Clutter - UI library based on OpenGL. GNU LGPL2.1

• giflib - Library for reading and writing gif images. MIT

• heman (⭐446) - Tiny library of image utilities dealing with height maps, normal maps, distance fields and the like. Expat

• libcaca (⭐427) - ASCII renderer for terminal-based interfaces. WTFPLv2

• libimagequant - Small, portable library for high-quality conversion of RGBA images to 8-bit indexed colour images. FreeBSD

• libjpeg-turbo - Faster library for reading and writing JPEG files. Various Licenses

• libpng - The official PNG reference library. libpng license

Graphical User Interface

• GTK+ - Cross-platform widget toolkit. GNU LGPL2.1

• IUP - Another cross-platform widget toolkit. Expat

• Tk - Basic widget toolkit. Part of Tcl/Tk. Tcl/Tk License

• XForms Toolkit - Widget toolkit designed for the XWindow system. GNU LGPL2.1

• nuklear (⭐13k) - Single-header ANSI C gui library. Public Domain

• libui (⭐10k) - Simple and portable (but not inflexible) GUI library. MIT

Hashing

• libcrc (⭐360) - Multi platform CRC library. MIT

• murmur (⭐2.1k) - C implementation of MurMur Hashing. Public Domain

JSON

• Jansson - C library for encoding, decoding and manipulating JSON. Expat

• jsmn - Minimalistic JSON parser. Expat

• json-c (⭐2.5k) - Library for working with JSON. Expat

• parson (⭐1.1k) - Lightweight JSON library written in C. MIT

• YAJL - Fast C JSON streaming parser library. ISC

Intermediate / Language Standards

• 8 gdb tricks you should know

Macros / Language Standards

• P99 - Suite of macros to implement advanced features like default function arguments, scope-bound resources, etc. (Requires C99) Q Public License

Memory Allocators / Language Standards

• dlmalloc - Doug Lea's malloc(3) implementation, useful for academic and research purposes. Public Domain

Multimedia / Language Standards

• FFMPEG - Complete, cross-platform solution to record, convert and stream audio and video. GNU LGPL2.1 or later or GNU GPL2.1 or later (some parts)

• GStreamer - Framework for audio and visual media. GNU LGPL2.1

• libsoup - GNOME HTTP client/server library. Uses GObject. GNU LGPL2.1

Numerical / Language Standards

• BLAS - Basic Linear Algebra Subprograms; a set of routines that provide vector and matrix operations. BLAS license

• FFTW - The Fastest Fourier Transform in the West; a highly-optimized fast Fourier transform routine. GNU GPL2.1 or later

• FLINT - Fast Library for Number Theory; a library supporting arithmetic with numbers, polynomials, power series and matrices, among others. GNU GPL2.1 or later

• PARI/GP - Computer algebra system for number theory; includes a compiler to C. GNU GPL2.1 or later

Parallel Programming / Language Standards

• cchan - Small library for channel constructs for inter-thread communication. Public Domain

• mill - Go-style concurrency in C. X11

• MPICH - Another implementation of MPI. MPICH licence

• pthreads - The POSIX thread library.

• TinyCThread - Portable, small implementation of the C11 threads API. zlib

Parsers / Language Standards

• hammer (⭐267) - Parser combinators for binary formats. GNU GPL2.1

• iniparser (⭐829) - Parser for .ini files. Expat

• mpc (⭐2.4k) - Parser combinator library. FreeBSD

• libucl (⭐1.5k) - Universal configuration library parser. FreeBSD

Regex / Language Standards

• SLRE (⭐499) - Super Light Regular Expression library; a very small implementation of a subset of Perl regex syntax. GNU GPL2.1

• TRE (⭐690) - POSIX-compliant, feature-full regex library. FreeBSD

Serialization / Language Standards

• c-capnproto (⭐67) - Implementation of the Cap'n Proto serialization protocol. Expat

• cmp (⭐286) - Implementation of the MessagePack serialization protocol. Expat

• mpack (⭐406) - Another implementation of the MessagePack serialization protocol. Expat

• netstring-c (⭐4) - Netstring encoder and decoder. Public Domain

• protobuf-c (⭐2.2k) - Implementation of Google Protocol Buffer in C. FreeBSD

• xdr - External Data Representation; a standard for data serialization.

Source Code Collections / Language Standards

• CCAN - Modelled after Perl's CPAN, this is a big collection of C code that does stuff. The full list is here.

• clib (⭐4.4k) - Something of a package manager for C. Comes with a bunch of libraries of its own (⭐4.4k). Expat

• gnulib - Collection of common GNU code.

• libdjb - Collection of libraries doing various things. (Apparently) Public Domain

Standard Libraries / Language Standards

• dietlibc - C standard library designed for the smallest possible binaries. GNU GPL2.1

• glibc - The GNU C Library; an implementation of the C standard library. GNU LGPL2.1

• musl - Standard C library, compatible with POSIX 2008 and C11. Designed for static linking. Expat

String Manipulation / Language Standards

• ICU - International Components for Unicode; a library for Unicode support. ICU license

• SDS (⭐4k) - 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 (⭐4.4k). FreeBSD

Testing / Language Standards

• CUnit - Another unit testing framework for C. GNU LGPL2.0

• Cutest (⭐18) - Library for unit testing with memory leak detection (Linux, freeBSD and Windows). GPL2

• minunit (⭐441) - Minimal unit testing framework for C. Expat

• munit - Small but full-featured unit testing framework for C with no dependencies. MIT

Atom / Language Standards

• linter-clang (⭐56) - Lint C code in Atom, using Clang. MIT

• linter-gcc (⭐71) - Lint C code in Atom, using GCC. MIT

Vim / Language Standards

• Syntastic (⭐11k) - Syntax checking and linting. Do What The Fuck You Want To license

Tools / Language Standards

• biicode - Modern dependency manager for C. Expat

• c (⭐2k) - Compile and execute C "scripts" in one go on the command line. Also has shebang support. Expat

• c99sh (⭐101) - Run C files using hash-bang. FreeBSD

• cdecl - Online service to translate C declarations into English and vice versa. Public Domain

• cinclude2dot - Graphs include dependencies in a C project using Graphviz. Any GNU GPL version (due to underspecification in the file)

• Glade - RAD tool to enable quick development of GTK+ GUIs. GNU GPL2.1

• tup - Very fast, file-based, cross-platform build system. GNU GPL2.1

• Valgrind - Range of dynamic analysis tools, including a leak checker. GNU GPL2.1

Utilities / Language Standards

• ApeTagLibs (⭐13) - C library for working with APEv2 tags. Expat

• CException (⭐251) - C implementation of exceptions. Expat

• docopt.c (⭐311) - C implementation of a command-line option parser. Expat

• dyncall - Another foreign function interface library. Expat

• FANN - Fast Artifical Neural Network library; an implementation of neural networks. GNU GPL2.1

• 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

• huffandpuff (⭐89) - Minimal Huffman encoder and decoder. Public Domain

• libffi (⭐2.6k) - Portable foreign-function interface library. Expat

• libimobiledevice (⭐5.2k) - Cross-platform protocol library to communicate with iThings. GNU LGPLv2.1 or later (library) or GNU GPL2.1 or later (tools)

• nope.c (⭐693) - C-language-based, ultra-light software platform for scalable server-side and networking applications (think node.js for C programmers). GNU GPL2.1

• pbc (⭐1.6k) - Protocol buffers library. Expat

• Ragel - DSL for state machines that compiles to C. GNU GPL2.1

• uthash - Hash table implementation, allowing existing structures to be stored in a hash table easily. 1-clause BSD

• libelf (⭐33) - ELF object file access library in C. GNU GPL2.1

• mcpp - Portable C preprocessor. 2-clause BSD

• Capstone (⭐6k) - Dissasembly/disassembler framework. BSD 3-clause

XML / Language Standards

• Expat - Stream-oriented XML parser. Expat

• libxml2 - Standards-compliant, portable XML parser. Expat

Deep Learning

• Darknet - Open source neural network framework written in C and CUDA. It is fast, easy to install, and supports CPU and GPU computation.

Editors

• Visual Studio Code - Code editing, redefined. Visual Studio Code.

Graphic APIs

• OpenGL - Industry adopted 2D and 3D graphics API. More resources at awesome-opengl (⭐1.7k).

• OpenGL ES - Industry adopted 2D and 3D graphics API for mobile and embedded devices.

• OpenGL SC - Graphic and compute standard for industry requiring system safety certification.

• Vulkan - Explicit graphic and compute API for modern cross-platform development. More resources at awesome-vulkan (⭐2.6k).

Reference

• SEI CERT C Coding Standard

• C FAQ - comp.lang.c Frequently Asked Questions

• Comparison of C/POSIX standard library implementations for GNU/Linux

• GNU C Reference Manual

• Robert Pike's notes on programming in C

• Draft ANSI C Rationale

• Draft C99 Rationale

Reference / Language Standards

• Draft ANSI C (C89) standard

• Draft C99 standard

• Draft C11 standard

• C: A Reference Manual 5E - Full reference book for C99.

• C Pocket Reference - Concise reference book for C99.

• The C Programming Language 2E - The original book on C, by its creators.

Beginner / Language Standards

• Building C Projects

• C Programming Wikibook

• Introduction to 'fun' C

• Learning C with GDB

• POSIX Threads Programming tutorial (a little dated, but most of it is still valid and useful)

• The GNU C Programming Tutorial (online PDF)

• Templating in C

• C Primer Plus 6E - Complete tutorial on programming in C11.

• C Programming: A Modern Approach - Excellent book to learn the basics of C.

• Head First C - 'Head-first' style book for learning C.

Intermediate / Language Standards

• 10 C99 tricks

• Diving into concurrency: trying out mutexes and atomics

• Introduction to OpenMP (video)

• OpenMP tutorial (for the OpenMP3 standard)

• memcpy vs memmove

• MPI tutorial

• Some unknown features or tricks in C language

• The lost art of C structure packing

• What every C programmer should know about undefined behaviour

• 21st Century C - Very good second programming book on C.

• Understanding and Using C Pointers - In-depth resource on pointers in C.

• ZeroMQ - Book for using ZeroMQ with C.

Advanced / Language Standards

• Advanced metaprogramming in C

• Quick tutorial on implementing and debugging malloc, free, calloc, and realloc

• Bit twiddling hacks

• I do not know C

• Implementing smart pointers for the C programming language

• Inline functions in C

• Metaprogramming custom control structures in C

• Some dark corners of C

• Writing efficient C and C code optimization

• What every programmer should know about memory

• Expert C Programming: Deep C Secrets - Interesting, in-depth and entertaining look at the innards of C.