2 Quick Installation Guide for musl libc
3 ======================================
5 There are many different ways to install musl depending on your usage
6 case. This document covers only the build and installation of musl by
7 itself, which is useful for upgrading an existing musl-based system or
8 compiler toolchain, or for using the provided musl-gcc wrapper with an
9 existing non-musl-based compiler.
11 Building complete native or cross-compiler toolchains is outside the
12 scope of this INSTALL file. More information can be found on the musl
13 website and community wiki.
19 The only build-time prerequisites for musl are GNU Make and a
20 freestanding C99 compiler toolchain targeting the desired instruction
21 set architecture and ABI, with support for gcc-style inline assembly,
22 weak aliases, and stand-alone assembly source files.
24 The system used to build musl does not need to be Linux-based, nor do
25 the Linux kernel headers need to be available.
27 If support for dynamic linking is desired, some further requirements
28 are placed on the compiler and linker. In particular, the linker must
29 support the -Bsymbolic-functions option.
31 At present, GCC 4.6 or later is the recommended compiler for building
32 musl. Any earlier version of GCC with full C99 support should also
33 work, but may be subject to minor floating point conformance issues on
34 i386 targets. Sufficiently recent versions of PCC and LLVM/clang are
35 also believed to work, but have not been tested as heavily; prior to
36 Fall 2012, both had known bugs that affected musl. Firm/cparser is
37 also believed to work but lacks support for producing shared
45 musl can be built for the following CPU instruction set architecture
49 * Minimum CPU model is actually 80486 unless kernel emulation of
50 the `cmpxchg` instruction is added
55 * EABI, standard or hard-float VFP variant
56 * Little-endian default; big-endian variants also supported
57 * Compiler toolchains only support armv4t and later
61 * Big-endian default; little-endian variants also supported
62 * Default ABI variant uses FPU registers; alternate soft-float ABI
63 that does not use FPU registers or instructions is available
64 * MIPS2 or later, or kernel emulation of ll/sc (standard in Linux)
68 * Only 32-bit is supported
69 * Compiler toolchain must provide 64-bit long double, not IBM
70 double-double or IEEE quad
71 * For dynamic linking, compiler toolchain must be configured for
75 * Big-endian default; little-endian variants also supported
77 * Requires support for lwx/swx instructions
79 The following additional targets are available for build, but may not
80 work correctly and may not yet have ABI stability:
83 * Little-endian by default; big-engian variant also supported
84 * Full FPU ABI or soft-float ABI is supported, but the
85 single-precision-only FPU ABI is not supported (musl always
86 requires IEEE single and double to be supported)
88 * x32 (x86_64 ILP32 ABI)
92 Build and Installation Procedure
93 --------------------------------
95 To build and install musl:
97 1. Run the provided configure script from the top-level source
98 directory, passing on its command line any desired options.
100 2. Run "make" to compile.
102 3. Run "make install" with appropriate privileges to write to the
105 The configure script attempts to determine automatically the correct
106 target architecture based on the compiler being used. For some
107 compilers, this may not be possible. If detection fails or selects the
108 wrong architecture, you can provide an explicit selection on the
109 configure command line.
111 By default, configure installs to a prefix of "/usr/local/musl". This
112 differs from the behavior of most configure scripts, and is chosen
113 specifically to avoid clashing with libraries already present on the
114 system. DO NOT set the prefix to "/usr", "/usr/local", or "/" unless
115 you're upgrading libc on an existing musl-based system. Doing so will
116 break your existing system when you run "make install" and it may be
117 difficult to recover.
121 Notes on Dynamic Linking
122 ------------------------
124 If dynamic linking is enabled, one file needs to be installed outside
125 of the installation prefix: /lib/ld-musl-$ARCH.so.1. This is the
126 dynamic linker. Its pathname is hard-coded into all dynamic-linked
127 programs, so for the sake of being able to share binaries between
128 systems, a consistent location should be used everywhere. Note that
129 the same applies to glibc and its dynamic linker, which is named
130 /lib/ld-linux.so.2 on i386 systems.
132 If for some reason it is impossible to install the dynamic linker in
133 its standard location (for example, if you are installing without root
134 privileges), the --syslibdir option to configure can be used to
135 provide a different location
137 At runtime, the dynamic linker needs to know the paths to search for
138 shared libraries. You should create a text file named
139 /etc/ld-musl-$ARCH.path (where $ARCH matches the architecture name
140 used in the dynamic linker) containing a list of directories where you
141 want the dynamic linker to search for shared libraries, separated by
142 colons or newlines. If the dynamic linker has been installed in a
143 non-default location, the path file also needs to reside at that
144 location (../etc relative to the chosen syslibdir).
146 If you do not intend to use dynamic linking, you may disable it by
147 passing --disable-shared to configure; this also cuts the build time
152 Checking for Successful Installation
153 ------------------------------------
155 After installing, you should be able to use musl via the musl-gcc
156 wrapper. For example:
162 printf("hello, world!\n");
166 /usr/local/musl/bin/musl-gcc hello.c
169 To configure autoconf-based program to compile and link against musl,
170 set the CC variable to musl-gcc when running configure, as in:
172 CC=musl-gcc ./configure ...
174 You will probably also want to use --prefix when building libraries to
175 ensure that they are installed under the musl prefix and not in the
176 main host system library directories.