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musl - an implementation of the standard library for Linux-based systems
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Rich Felker c4694f4061 rewrite bump allocator to fix corner cases, decouple from expand_heap 
this affects the bump allocator used when static linking in programs
that don't need allocation metadata due to not using realloc, free,
etc.

commit e3bc22f1ef refactored the bump
allocator to share code with __expand_heap, used by malloc, for the
purpose of fixing the case (mainly nommu) where brk doesn't work.
however, the geometric growth behavior of __expand_heap is not
actually well-suited to the bump allocator, and can produce
significant excessive memory usage. in particular, by repeatedly
requesting just over the remaining free space in the current
mmap-allocated area, the total mapped memory will be roughly double
the nominal usage. and since the main user of the no-brk mmap fallback
in the bump allocator is nommu, this excessive usage is not just
virtual address space but physical memory.

in addition, even on systems with brk, having a unified size request
to __expand_heap without knowing whether the brk or mmap backend would
get used made it so the brk could be expanded twice as far as needed.
for example, with malloc(n) and n-1 bytes available before the current
brk, the brk would be expanded by n bytes rounded up to page size,
when expansion by just one page would have sufficed.

the new implementation computes request size separately for the cases
where brk expansion is being attempted vs using mmap, and also
performs individual mmap of large allocations without moving to a new
bump area and throwing away the rest of the old one. this greatly
reduces the need for geometric area size growth and limits the extent
to which free space at the end of one bump area might be unusable for
future allocations.

as a bonus, the resulting code size is somewhat smaller than the
combined old version plus __expand_heap.
2020-06-03 18:13:18 -04:00
arch fix incorrect SIGSTKFLT on all mips archs 2020-05-21 16:25:12 -04:00
compat/time32 fix null pointer dereference in setitimer time32 compat shim 2019-12-08 10:35:04 -05:00
crt remove unnecessary and problematic _Noreturn from crt/ldso startup 2019-06-25 19:05:40 -04:00
dist add another example option to dist/config.mak 2012-04-24 16:49:11 -04:00
include remove duplicate definitions of INET[6]_ADDRSTRLEN 2020-03-04 12:33:35 -05:00
ldso move declaration of interfaces between malloc and ldso to dynlink.h 2020-06-02 21:38:25 -04:00
src rewrite bump allocator to fix corner cases, decouple from expand_heap 2020-06-03 18:13:18 -04:00
tools fix incorrect escaping in add-cfi.*.awk scripts 2020-01-20 15:57:29 -05:00
.gitignore remove obsolete gitignore rules 2016-07-06 00:21:25 -04:00
.mailmap update contributor name 2019-12-07 12:21:35 -05:00
configure suppress unwanted warnings when configuring with clang 2020-06-01 20:59:53 -04:00
COPYRIGHT update COPYRIGHT year 2020-01-01 11:17:20 -05:00
dynamic.list fix regression in access to optopt object 2018-11-19 13:20:41 -05:00
INSTALL document mips r6 in INSTALL file 2019-09-27 00:22:48 -04:00
Makefile fix failure to build time32 compat shims with out-of-tree builds 2019-11-04 01:47:38 -05:00
README update version reference in the README file 2014-06-25 14:16:53 -04:00
VERSION release 1.2.0 2020-02-20 19:37:02 -05:00
WHATSNEW release 1.2.0 2020-02-20 19:37:02 -05:00

README 

    musl libc

musl, pronounced like the word "mussel", is an MIT-licensed
implementation of the standard C library targetting the Linux syscall
API, suitable for use in a wide range of deployment environments. musl
offers efficient static and dynamic linking support, lightweight code
and low runtime overhead, strong fail-safe guarantees under correct
usage, and correctness in the sense of standards conformance and
safety. musl is built on the principle that these goals are best
achieved through simple code that is easy to understand and maintain.

The 1.1 release series for musl features 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.

For basic installation instructions, see the included INSTALL file.
Information on full musl-targeted compiler toolchains, system
bootstrapping, and Linux distributions built on musl can be found on
the project website:

    http://www.musl-libc.org/