|author||Rich Felker <email@example.com>||2012-10-26 20:14:19 -0400|
|committer||Rich Felker <firstname.lastname@example.org>||2012-10-26 20:14:19 -0400|
2 files changed, 67 insertions, 33 deletions
@@ -5,35 +5,68 @@ musl may be installed either as an alternate C library alongside the
existing libraries on a system, or as the primary C library for a new
or existing musl-based system.
-First, some prerequisites:
+This document covers the prerequisites and procedures for compiling
-- A C99 compiler with gcc-style inline assembly support, support for
- weak aliases, and support for building stand-alone assembly files.
- gcc 3.x and 4.x are known to work. pcc and LLVM/clang may work but
- are untested, and pcc is known to have some bugs.
-- GNU make
-- Linux, preferably 2.6.22 or later. Older versions are known to have
- serious bugs that will make some interfaces non-conformant, but if
- you don't need threads or POSIX 2008 features, even 2.4 is probably
+==== Build Prerequisites ====
-- A supported CPU architecture (currently i386, x86_64, arm, or mips).
+The only build-time prerequisites for musl are GNU Make and a
+freestanding C99 compiler toolchain targeting the desired instruction
+set architecture and ABI, with support for gcc-style inline assembly,
+weak aliases, and stand-alone assembly source files.
-- If you want to use dynamic linking, it's recommended that you have
- permissions to write to /lib and /etc. Otherwise your binaries will
- have to use a nonstandard dynamic linker path.
+The system used to build musl does not need to be Linux-based, nor do
+the Linux kernel headers need to be available.
+If support for dynamic linking is desired, some further requriements
+are placed on the compiler and linker. In particular, the linker must
+support the -Bsymbolic-functions option.
+At present, GCC 4.6 or later is the recommended compiler for building
+musl. Any earlier version of GCC with full C99 support should also
+work, but may be subject to minor floating point conformance issues on
+i386 targets. Sufficiently recent versions of PCC and LLVM/clang are
+also believed to work, but have not been tested as heavily; prior to
+Fall 2012, both had known bugs that affected musl.
-== Option 1: Installing musl as an alternate C library ==
+=== Supported Targets ====
+musl can be built for the following CPU instruction set architecture
+and ABI combinations:
+- i386 (requires 387 math and 486 cmpxchg instructions)
+- arm (EABI)
+- mips (o32 ABI, requires fpu or float emulation in kernel)
+- microblaze (requires a cpu with lwx/swx instructions)
+For architectures with both little- and big-endian options, both are
+supported unless otherwise noted.
+In general, musl assumes the availability of all Linux syscall
+interfaces available in Linux 2.6.0. Some programs that do not use
+threads or other modern functionality may be able to run on 2.4.x
+kernels. Other kernels (such as BSD) that provide a Linux-compatible
+syscall ABI should also work but have not been extensively tested.
+==== Option 1: Installing musl as an alternate C library ====
In this setup, musl and any third-party libraries linked to musl will
reside under an alternate prefix such as /usr/local/musl or /opt/musl.
A wrapper script for gcc, called musl-gcc, can be used in place of gcc
to compile and link programs and libraries against musl.
+(Note: There are not yet corresponding wrapper scripts for other
+compilers, so if you wish to compile and link against musl using
+another compiler, you are responsible for providing the correct
+options to override the default include and library search paths.)
To install musl as an alternate libc, follow these steps:
1. Configure musl's build with a command similar to:
@@ -92,7 +125,7 @@ source/build tree.
-== Option 2: Installing musl as the primary C library ==
+==== Option 2: Installing musl as the primary C library ====
In this setup, you will need an existing compiler/toolchain. It
shouldnt matter whether it was configured for glibc, uClibc, musl, or
@@ -8,7 +8,7 @@ musl is an alternative to glibc, eglibc, uClibc, dietlibc, and klibc.
For reasons why one might prefer musl, please see the FAQ and libc
comparison chart on the project website,
For installation instructions, see the INSTALL file.
@@ -19,22 +19,23 @@ license status of code included in musl (standard MIT license).
-With the 0.9.0 release, musl has reached a milestone in completeness
-and compatibility. All interfaces in ISO C99 and POSIX 2008 base exist
-in musl, along with a number of non-standardized interfaces based on
-GNU and BSD libraries and syscall interfaces for Linux-kernel-specific
-functions. Some interfaces lack obscure or rarely-used functionality
-needed for strict conformance, but the vast majority of interfaces go
-above and beyond the requirements for conformance, often promising
-success where other implementations can fail under resource exhaustion
-or other corner-case conditions.
-At this point, hundreds of packages have been successfully built
-against musl - either out-of-the-box or with minor patches to address
-portability errors - ranging from low-level system utilities and
-network daemons to major gui applications. Testing has been conducted
-using three separate test frameworks and numerous additional
-standalone test cases to verify the correctness of the implementation.
+The 0.9.x release series for musl features interface coverage for all
+interfaces defined in ISO C99 and POSIX 2008 base, along with a number
+of non-standardized interfaces for compatibility with Linux, BSD, and
+glibc functionality. As the release series progresses, we are
+gradually adding support for incomplete functionality in existing
+interfaces, additional functions that are deemed to be important due
+to their use in real-world software, and support for new library and
+language features in C11 such as thread-local storage, which is now
+supported on all targets. In addition, support for additional target
+cpu architectures is being added.
+The number of packages build successfully against musl - either
+out-of-the-box or with minor patches to address portability errors -
+has exceeded 5000 and is steadily growing. In addition to application
+compatibility testing, unit testing has been conducted using three
+separate test frameworks and numerous additional standalone test cases
+to verify the correctness of the implementation.
Included with this package is a gcc wrapper script (musl-gcc) which
allows you to build musl-linked programs using an existing gcc 3.x or