path: root/include/errno.h
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2018-10-16restore attribute((const)) to pthread_self and errno location declsRich Felker-0/+3
revert commit a603a75a72bb469c6be4963ed1b55fabe675fe15. as a result of commit 1c84c99913bf1cd47b866ed31e665848a0da84a2 this is now safe, assuming an interpretation of the somewhat-underspecified attribute((const)) consistent with real-world usage.
2015-09-17remove attribute((const)) from pthread_self and errno location declsRich Felker-3/+0
this attribute was applied to pthread_self and the functions providing the locations for errno and h_errno as an optimization; however, it is subtly incorrect. as specified, it means the return value will always be the same, which is not true; it varies per-thread. this attribute also implies that the function does not depend on any state, and that calls to it can safely be reordered across any other code. however such reordering is unsafe for these functions: they break when reordered before initialization of the thread pointer. such breakage was actually observed when compiled by libfirm/cparser. to some extent the reordering problem could be solved with strong compiler barriers between the stages of early startup code, but the specified meaning of of attribute((const)) is sufficiently strong that a compiler would theoretically be justified inserting gratuitous calls to attribute((const)) const functions at random locations (e.g. to save the value in static storage for later use). this reverts commit cbf35978a9870fb1f5c73a852c986d4fcca6c2d4.
2013-04-06add support for program_invocation[_short]_nameRich Felker-0/+6
this is a bit ugly, and the motivation for supporting it is questionable. however the main factors were: 1. it will be useful to have this for certain internal purposes anyway -- things like syslog. 2. applications can just save argv[0] in main, but it's hard to fix non-portable library code that's depending on being able to get the invocation name without the main application's help.
2012-01-26remove useless "extern" keywords in headersRich Felker-1/+1
2011-06-06use __attribute__((const)) for errno and pthread_self if __GNUC__ is definedRich Felker-0/+3
this is not too ugly and should result in significant code size and performance improvements for many programs.
2011-02-12initial check-in, version 0.5.0v0.5.0Rich Felker-0/+18