libc11: C11 standard library

libc11 is a public domain implementation of the C11 (ISO/IEC 9899:2011) standard library.

Features

• Supports the Linux, FreeBSD, OpenBSD, NetBSD, Solaris, and Mac OS X platforms.
• Currently targets the System V ABI for x86 and x86-64, and the EABI for ARM.
• Clean and modular design, most features can be omitted when building.
• No build prerequisites beyond a GNU-compatible toolchain and a C99 compiler.
• 100% free and unencumbered public domain software, usable in any context and for any purpose.

Current Status

This table summarizes which C11 features are implemented at present:

Header	Spec	Description	Status
<assert.h> <complex.h>	C11 7.2 C11 7.3	Diagnostics. Complex arithmetic.	WIP
<ctype.h>	C11 7.4	Character handling.	Implemented.
<errno.h> <fenv.h>	C11 7.5 C11 7.6	Errors. Floating-point environment.	Implemented.1
<float.h>	C11 7.7	Characteristics of floating types.	Implemented.
<inttypes.h>	C11 7.8	Format conversion of integer types.	WIP
<iso646.h>	C11 7.9	Alternative spellings.	Implemented.
<limits.h>	C11 7.10	Sizes of integer types.	Implemented.
<locale.h>	C11 7.11	Localization.	Stubbed.
<math.h> <setjmp.h>	C11 7.12 C11 7.13	Mathematics. Nonlocal jumps.	WIP
<signal.h>	C11 7.14	Signal handling.	WIP
<stdalign.h>	C11 7.15	Alignment.	Implemented.
<stdarg.h>	C11 7.16	Variable arguments.	Implemented.2
<stdatomic.h>	C11 7.17	Atomics.	WIP
<stdbool.h>	C11 7.18	Boolean type and values.	Implemented.
<stddef.h>	C11 7.19	Common definitions.	Implemented.
<stdint.h>	C11 7.20	Integer types.	WIP
<stdio.h>	C11 7.21	Input/output.	WIP
<stdlib.h>	C11 7.22	General utilities.	WIP
<stdnoreturn.h>	C11 7.23	_Noreturn.	Implemented.
<string.h> <tgmath.h> <threads.h> <time.h> <uchar.h>	C11 7.24 C11 7.25 C11 7.26 C11 7.27 C11 7.28	String handling. Type-generic math. Threads. Date and time. Unicode utilities.	WIP
<wchar.h>	C11 7.29	Wide character utilities.	Omitted.3
<wctype.h>	C11 7.30	Wide character utilities.	Omitted.4

Footnotes

Platform Support

Platform	Architecture	Binary Interface	Compilers
Bare metal	any	N/A	Clang, GCC
Linux	ARMv6+5	ARM EABI	Clang, GCC
Linux	x86	i386 SysV ABI	Clang, GCC
Linux	x86-64	AMD64 SysV ABI	Clang, GCC
FreeBSD	x86-64	AMD64 SysV ABI	Clang, GCC
OpenBSD	x86-64	AMD64 SysV ABI	Clang, GCC
NetBSD	x86-64	AMD64 SysV ABI	Clang, GCC
Solaris	x86-64	AMD64 SysV ABI	Clang, GCC
Mac OS X	x86-64	AMD64 SysV ABI	Clang, GCC

Footnotes

See http://build.libc11.org for the current build status on all supported platforms.

Installation

Installing on Unix

Configuring, building, and installing the library (by default, into /usr/local) are all performed with the standard incantations:

$ ./autogen.sh       # for a development checkout only
$ ./configure
$ make
$ sudo make install

Configuration

Configuring a Static Build

By default on most platforms that support both, the library will be built both as a static library (libc.a) as well as a dynamic shared library (libc.so on most Unix systems, though libc.dylib on Darwin).

If you don't require a shared library, configure the build accordingly:

$ ./configure --disable-shared

Configuring a Minimal Build

The library is thoroughly modular. Specific header files and their underlying function implementations can be omitted using the familiar ./configure --disable-FEATURE facility provided by Autoconf.

For example, if you don't require any numerics support, you might as well disable the floating-point routines and the mathematics library, as follows:

$ ./configure --disable-complex --disable-fenv --disable-float --disable-math

To review the list of features, see the output of ./configure --help.

Configuring for Bare Metal

The special none target operating system builds the library with a system-call interface where all system operations are simply no-op stubs. See the sys/syscall.h header file and the sys/posix/none/ directory for the syscall stubs that a bare-metal user of libc11 must implement.

The following example shows how one might configure a cross-compilation build on an x86-64 Linux system, targeting an x86-64 bare-metal system:

$ ./configure --build=x86_64-unknown-linux-gnu --host=x86_64-unknown-none

Provided your linker supports weak symbols, you can configure the libc11 build as per the aforementioned example, and then when linking libc11 into your kernel provide your own syscall implementations as strong symbols that override the default no-op stubs from sys/posix/none/.

Elsewhere

Find this project at: GitHub, Bitbucket, Open Hub, SourceForge, Travis CI, Coverity Scan, Twitter, Tumblr, and COD5. See also the project's Buildbot.

Many other open-source implementations of the C standard library exist, though most of them are licensed more restrictively than this implementation:

Project	License	Status	x86	x86-64	ARM	ARM64	MIPS	MIPS64	Miscellaneous
PDCLib	PD/CC0	Active	Yes	Yes	?	?	?	?	incomplete
PDPCLIB	PD	Active?	Yes	No	No	No	No	No	S/3x0
Bionic	BSD	Active	Yes	Yes	Yes	Yes	Yes	Yes	for Android
dietlibc	GPL	Active?	Yes	Yes	Yes	No	Yes	Yes	many targets
EGLIBC	LGPL	Inactive	Yes	Yes	Yes	Yes	Yes	Yes	discontinued
glibc	LGPL	Active	Yes	Yes	Yes	Yes	Yes	Yes	many targets
klibc	GPL/BSD	Active	Yes	Yes	Yes	No	Yes	Yes	many targets
musl	MIT	Active	Yes	Yes	Yes	No	Yes	No	PPC, MicroBlaze
Newlib	LGPL/BSD/etc	Active	Yes	Yes	Yes	Yes	Yes	Yes	many targets
olibc	BSD	Active?	Yes	Yes	Yes	Yes	Yes	Yes	fork of Bionic
OSv	MIT/BSD	Active	No	Yes	No	Yes	No	No	written in C++
uClibc	LGPL	Active	Yes	Yes	Yes	No	Yes	Yes	many targets

Author

This project is part of the DRY initiative.

• Arto Bendiken - http://ar.to/

Contributors

• Vlad Gluhovsky
• Syed Nasim
• Samuel Sarle

Donations

If you found this software useful and would like to encourage its maintenance and further development, please consider making a $5 donation to the author(s) via Gratipay or Bitcoin.

License

This is free and unencumbered public domain software. For more information, see http://unlicense.org/ or the accompanying UNLICENSE file.

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1. Thread-local storage not supported as yet.↩

2. Currently implemented only for the Clang and GCC compilers.↩

3. Legacy wide-character support purposely omitted from the library.↩

4. Legacy wide-character support purposely omitted from the library.↩

5. The armhf architecture providing a hardware floating-point unit (FPU).↩