|author||Rich Felker <firstname.lastname@example.org>||2015-09-17 04:45:01 +0000|
|committer||Rich Felker <email@example.com>||2015-09-17 04:45:01 +0000|
remove attribute((const)) from pthread_self and errno location decls
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.
Diffstat (limited to 'arch')
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