C

Yasm Modular Assembler Project. `2-clause BSD`

Compiler cache designed to speedup recompilation. `GNU GPL3 or later`

C compiler for LLVM. Supports C11. `NCSA`

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

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

Compiler for a variant of the C language, for single program, multiple data programming. `Various licenses`

Venerable C compiler. Supports C99. `Various free licenses`

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

Generic lossless compression algorithm based on LZ77, Huffman coding and 2nd order context modelling `MIT`

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

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

Fast Compression algorithm.

Very fast data compression library. `GNU GPL2.1`

Pixz (pronounced pixie) is a parallel, indexing version of `xz`. `2-clause BSD`

Fast compression library. `GNU GPL2.1`

Fast compression library (implementation in C++, native bindings to C).

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

Fast real-time compression algorithm `3-clause BSD`

Secure communication library, implementing SSL, TLS and DTLS. `GNU LGPL2.1 or later`

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

Modernized fork of OpenSSL. `Various Licenses`

Modern and easy-to-use crypto library. `Expat`

Fairly comprehensive, modular and portable cryptographic toolkit. `Public Domain`

Another crypto implementation for C. `Apache 2.0`

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

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

Minimalistic client library for Redis. `3-clause BSD`

Ultra-fast, ultra-compact key-value embedded data store. `OpenLDAP License`

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

High-performance client library for MongoDB. `Apache 2.0`

Powerful object-relational database system. `PostgreSQL licence`

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

Advanced key-value store. `3-clause BSD`

Modern, embeddable key-value database. `FreeBSD`

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

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

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

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

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

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

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

The GNOME IDE. `GNU GPL2.1`

Hackable text editor for the 21st century. `MIT`

Extensible, configurable IDE supporting C. `GNU GPL3`

Cross-platform IDE. `GNU GPL2.1`

IDE written in Java. `EPL`

Very small and fast IDE. `GNU GPL2.1 or later`

The KDE IDE. `GNU GPL2.1`

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

Code editing, redefined. Visual Studio Code.

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

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

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

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

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

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

Minimalist environment for C development on Windows with 64 bit support. `Various Licenses`

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

Collection of common algorithms and data structures for C. `ISC`

Header only, macro generated, generic and type-safe Collections in C. `MIT`

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

Large collection of useful data structures and functions.

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

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

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

Lightweight library of C functions and structures. `GNU GPL2.1`

Safe Real-Time library for C. `3-clause BSD`

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

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

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

Range of single-file libraries for C. `Public Domain`

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

Fast and lightweight 2D game physics library. `Expat`

Game engine in pure C. `FreeBSD`

Binding for SFML in C. `zlib`

Modified version of the Quake2 engine. `GNU GPL2.1`

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

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

The Quake3 engine, freed at last. `GNU GPL2.1`

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

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

The Quake engine. `GNU GPL2.1`

The Quake2 engine. `GNU GPL2.1`

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

The reference frontend for libretro. `GNU GPL3`

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`

Engine designed for FPS games. `GNU GPL3 or later`

Small and lightweight implementations of common algorithms and data structures. `MIT`

Cross-platform widget toolkit. `GNU LGPL2.1`

Another cross-platform widget toolkit. `Expat`

Small C library for building user interfaces with C, XML and CSS. `MIT`

Simple and portable (but not inflexible) GUI library. `MIT`

Single-header ANSI C gui library. `Public Domain`

Basic widget toolkit. Part of Tcl/Tk. `Tcl/Tk License`

Widget toolkit designed for the XWindow system. `GNU LGPL2.1`

2D graphics library. `GNU LGPL2.1` or `MPLv1.1`

UI library based on OpenGL. `GNU LGPL2.1`

GPU graphics and utilities API. `Expat`

Library for reading and writing gif images. `MIT`

Tiny library of image utilities dealing with height maps, normal maps, distance fields and the like. `Expat`

ASCII renderer for terminal-based interfaces. `WTFPLv2`

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

Faster library for reading and writing JPEG files. `Various Licenses`

The official PNG reference library. `libpng license`

Function library for rasterizing 2D vector graphics. `GNU GPL3 or later`

Improved JPEG encoder. `3-clause BSD`

Industry adopted 2D and 3D graphics API. More resources at awesome-opengl.

Industry adopted 2D and 3D graphics API for mobile and embedded devices.

Graphic and compute standard for industry requiring system safety certification.

Explicit graphic and compute API for modern cross-platform development. More resources at awesome-vulkan.

Fast hashtable implementation. `Apache 2.0`

Multi platform CRC library. `MIT`

C implementation of MurMur Hashing. `Public Domain`

Fast Positive Hash library. `zlib`

Extremely fast non-cryptographic hash algorithm. `2-clause BSD`

Modern Computer Vision Library. `3-clause BSD`

C library for encoding, decoding and manipulating JSON. `Expat`

Minimalistic JSON parser. `Expat`

Library for working with JSON. `Expat`

Lightweight JSON library written in C. `MIT`

Advanced JSON manipulation library, with support for JSON Schema. `LGPL, any version`

Fast C JSON streaming parser library. `ISC`

Very good *second* programming book on C.

Concise reference book for C99.

Complete tutorial on programming in C11.

Excellent book to learn the basics of C.

Full reference book for C99.

Interesting, in-depth and *entertaining* look at the innards of C.

'Head-first' style book for learning C.

(video)

(for the OpenMP3 standard)

(a little dated, but most of it is still valid and useful)

The original book on C, by its creators.

(online PDF)

In-depth resource on pointers in C.

Book for using ZeroMQ with C.

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

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

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

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

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

Cross platform, lock-free memory allocator. `Public Domain`

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)`

Framework for audio and visual media. `GNU LGPL2.1`

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

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

GNOME HTTP client/server library. Uses GObject. `GNU LGPL2.1`

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

Compiler of ASN.1 specifications into C source code. `FreeBSD`

Microframework for C based on GLib. `GNU LGPLv2.1`

High-level binding for ZeroMQ. `MPL2.0`

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

Asynchronous networking library. `MIT`

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

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

Secure communication library, implementing SSL, TLS and DTLS. `GNU LGPL2.1 or later`

HTML5 parsing library in C99. `Apache 2.0`

Optimized HTTP/1, HTTP/2 high performance server/library. `MIT`

HTTP request/response parser. `Expat`

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

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

Library to simplify DNS programming. `3-clause BSD`

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

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

Yet another event loop. `FreeBSD`

Event loop replacement for network servers. `3-clause BSD`

Generic Security Service. `GNU GPL3 or later`

Library to add basic web server capabilities to an application or embedded device. `GNU GPL2`

Implementation of the Stringprep, Punycode and IDNA specifications. `GNU GPL3 or later`

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

Library for building simple and elegant cross-platform mmo client-server solutions. `Apache 2.0`

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

Cross-platform asynchronous I/O. `Expat`

Your friendly e-mail address validation library. `WTFPLv2`

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

Embedded web server for C. `GNU GPL2.1`

Portable MQTT C client for embedded systems and PCs alike. `MIT`

C-based implementation of ZeroMQ. `Expat`

C library to create simple HTTP servers and Web Applications. `Apache 2.0`

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

SIP implementation in C without additional dependencies. `GNU LGPLv2.1 or later`

Linux packet crafting tool. `GPL2`

C99 implementation of the TLS/SSL protocols, designed to be simple, fast and with security as a priority. `Apache 2.0`

C99 wrapper for the BSD sockets API. `ISC`

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

Mini C library for interacting with the Twitter OAuth API. `Expat`

Library for statistical and scientific computing. `GNU GPL2.1`

Automatically Tuned Linear Algebra Software. `3-clause BSD`

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

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)

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`

Library for multidimensional numerical integration. `GNU LGPLv3`

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

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

GNU Linear Programming Kit; a package designed for solving large-scale linear programming, mixed integer programming and other related problems. `GNU GPL3 or later`

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

Library for complex number arithmetic. `GNU LGPL3 or later`

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

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

The GNU Scientific Library; a sophisticated numerical library. `GNU GPL3`

Library for creating and manipulating large graphs. `GNU GPL2`

Very simple fast Fourier transform library. `3-clause BSD`

C interface to LAPACK. `3-clause BSD`

Computer algebra system for number theory; includes a compiler to C. `GNU GPL2.1 or later`

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

Library that handles various discrete and continuous probability density functions. `GNU LGPL3`

Very fast, SIMD-optimized mathematical library. `3-clause BSD`

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

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

Structured concurrency in C. `X11`

Go-style concurrency in C. `X11`

Another implementation of MPI. `MPICH licence`

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

Message passing interface implementation. `3-clause BSD`

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

The POSIX thread library.

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

Portable, small implementation of the C11 threads API. `zlib`

Parser combinators for binary formats. `GNU GPL2.1`

Parser for `.ini` files. `Expat`

Yet another INI parser. `GNU GPL3 or later`

Universal configuration library parser. `FreeBSD`

YAML 1.1 parser and emitter. `Expat`

Parser combinator library. `FreeBSD`

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

Simple and complete implementation of regular expressions with its own sintax. `GNU GPL3 or later`

Super Light Regular Expression library; a very small implementation of a subset of Perl regex syntax. `GNU GPL2.1`

Non-backtracking NFA/DFA-based Perl-compatible regex engine library. `3-clause BSD`

POSIX-compliant, feature-full regex library. `FreeBSD`

Binary serialization format meant to be compact, fast and easy-to-use. `Apache 2.0`

Implementation of the Cap'n Proto serialization protocol. `Expat`

Implementation of the MessagePack serialization protocol. `Expat`

C implementation of the Avro data serialization system. `Apache 2.0`

Another implementation of the MessagePack serialization protocol. `Expat`

Netstring encoder and decoder. `Public Domain`

Implementation of Google Protocol Buffer in C. `FreeBSD`

External Data Representation; a standard for data serialization.

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

Something of a package manager for C. Comes with a bunch of libraries of its own. `Expat`

Collection of common GNU code.

Collection of libraries doing various things. `(Apparently) Public Domain`

Google's C standard library, developed for Android. `3-clause BSD`

C standard library designed for the smallest possible binaries. `GNU GPL2.1`

The GNU C Library; an implementation of the C standard library. `GNU LGPL2.1`

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

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

International Components for Unicode; a library for Unicode support. `ICU license`

Text conversion library. `GNU LGPL2.1 (library)` or `GNU GPL3 (*iconv* program)`

Library for manipulating Unicode strings in C. `GNU LGPL3`

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. `FreeBSD`

Compressor for small text strings. `Expat`

Efficient string compression library. `3-clause BSD`

Single header utf8 string functions. `Unlicense`

Small, clean library for processing UTF-8 Unicode data. `License`

Very simple unit testing framework. `FreeBSD`

Unit testing framework for C. `GNU LGPL2.1`

Mock/stub generator for C. `Expat`

Unit testing framework with support for mock objects. `Apache 2.0`

KISS, non-intrusive C test framework. `Expat`

Another unit testing framework for C. `GNU LGPL2.0`

Library for unit testing with memory leak detection (Linux, freeBSD and Windows). `GPL2`

Minimal unit testing framework for C. `Expat`

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

Simple unit testing framework for C. `Expat`

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

Modern syntax checking. For C, it can use either GCC or Clang as a back-end. `GNU GPL3 or later`

Lint C code in Atom, using Clang. `MIT`

Lint C code in Atom, using GCC. `MIT`

Syntax checking and linting. `Do What The Fuck You Want To license`

Template system, with C templates for common code snippets. `GNU GPL3 or later`

Code completion engine for Vim. `GNU GPL3`

Fast memory error detector. `Apache 2.0`

Fast and small automatic source code formatter that supports C. `GNU LGPL3`

Modern dependency manager for C. `Expat`

Compile and execute C "scripts" in one go on the command line. Also has shebang support. `Expat`

Run C files using hash-bang. `FreeBSD`

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

Online service to translate C declarations into English and vice versa. `Public Domain`

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

Tool for measuring the complexity of C source code. `GNU GPL3 or later`

Source code analyzer and refactoring browser for collections of C programs. `GNU GPL3`

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

The GNU Project debugger; a debugger for C. `GNU GPL3 or later`

RAD tool to enable quick development of GTK+ GUIs. `GNU GPL2.1`

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

Source code tagging tool which works with C. `GNU GPL3`

Performance analysis tool. Part of GNU binutils. `GNU GPL3 or later`

Converts source code to formatted text with nice highlighting. `GNU GPL3`

Helps find unecessary inclusions and make suggestions for fixing them. Based on LLVM/Clang (and only works with it). `NCSA`

Formats C source code automatically to make it easier to read. Also converts from one style of source to another. `GNU GPLv3 or later`

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

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

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

Range of dynamic analysis tools, including a leak checker. `GNU GPL2.1`

Userspace library to interact with ALSA. `LGPL2.1`

C library for working with APEv2 tags. `Expat`

Library for manipulating binary object files. Part of GNU binutils. `GNU GPL3 or later`

Dissasembly/disassembler framework. `BSD 3-clause`