Rich Felker
7586360bad
modern (4.7.x and later) gcc uses init/fini arrays, rather than the legacy _init/_fini function pasting and crtbegin/crtend ctors/dtors system, on most or all archs. some archs had already switched a long time ago. without following this change, global ctors/dtors will cease to work under musl when building with new gcc versions. the most surprising part of this patch is that it actually reduces the size of the init code, for both static and shared libc. this is achieved by (1) unifying the handling main program and shared libraries in the dynamic linker, and (2) eliminating the glibc-inspired rube goldberg machine for passing around init and fini function pointers. to clarify, some background: the function signature for __libc_start_main was based on glibc, as part of the original goal of being able to run some glibc-linked binaries. it worked by having the crt1 code, which is linked into every application, static or dynamic, obtain and pass pointers to the init and fini functions, which __libc_start_main is then responsible for using and recording for later use, as necessary. however, in neither the static-linked nor dynamic-linked case do we actually need crt1.o's help. with dynamic linking, all the pointers are available in the _DYNAMIC block. with static linking, it's safe to simply access the _init/_fini and __init_array_start, etc. symbols directly. obviously changing the __libc_start_main function signature in an incompatible way would break both old musl-linked programs and glibc-linked programs, so let's not do that. instead, the function can just ignore the information it doesn't need. new archs need not even provide the useless args in their versions of crt1.o. existing archs should continue to provide it as long as there is an interest in having newly-linked applications be able to run on old versions of musl; at some point in the future, this support can be removed.
musl libc - a new standard library to power a new generation of
Linux-based devices. musl is lightweight, fast, simple, free, and
strives to be correct in the sense of standards-conformance and
safety.
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,
http://www.musl-libc.org/
For installation instructions, see the INSTALL file.
Please refer to the COPYRIGHT file for details on the copyright and
license status of code included in musl (standard MIT license).
Greetings!
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
4.x toolchain on the host. There are also now at several mini
distributions (in the form of build scripts) which provide a
self-hosting musl-based toolchain and system root. These are much
better options than the wrapper script if you wish to use dynamic
linking or build packages with many library dependencies. See the musl
website for details.
The musl project is actively seeking contributors, mostly in the areas
of porting, testing, and application compatibility improvement. For
bug reports, support requests, or to get involved in development,
please visit #musl on Freenode IRC or subscribe to the musl mailing
list by sending a blank email to musl-subscribe AT lists DOT openwall
DOT com.
Thank you for using musl.
Cheers,
Rich Felker / dalias