Musl

For the American lottery organization MUSL, see Multi-State Lottery Association.

musl is a C standard library intended for operating systems based on the Linux kernel, released under the MIT License.^[3] It was developed by Rich Felker to write a clean, efficient, and standards-conformant libc implementation.^[4]

musl
Developer(s)	Rich Felker (dalias) and others
Initial release	February 11, 2011; 14 years ago (2011-02-11)[1]
Stable release	1.2.5[2] / February 29, 2024; 19 months ago (2024-02-29)
Repository	git.musl-libc.org/cgit/musl
Operating system	Linux 2.6 or later
Platform	x86, x86_64, ARM, loongarch64, MIPS, Microblaze, PowerPC, powerpc64, x32, RISC-V, OpenRISC, s390x, SuperH
Type	C standard library Linux for embedded systems Linux for mobile devices
License	MIT License
Website	musl.libc.org

Overview

musl was designed from scratch to allow efficient static linking and to have realtime-quality robustness by avoiding race conditions, internal failures on resource exhaustion, and various other bad worst-case behaviors present in existing implementations.^[4] The dynamic runtime is a single file with stable ABI allowing race-free updates and the static linking support allows an application to be deployed as a single portable binary without significant size overhead.

It claims compatibility with the POSIX 2008 specification and the C11 standard. It also implements most of the widely used non-standard Linux, BSD, and glibc functions.^[5] There is partial ABI compatibility with the part of glibc required by Linux Standard Base.^[6]

Version 1.2.0 has support for (no longer current) Unicode 12.1.0 (while still having full UTF-8 support,^[7] more conformant/strict than glibc), and version 1.2.1 "features the new 'mallocng' malloc implementation, replacing musl's original dlmalloc-like allocator that suffered from fundamental design problems."^[2]