| Age | Commit message (Collapse) | Author | Lines |
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| 2018年09月26日 | fix aliasing-based undefined behavior in string functions | Rich Felker | -1/+7 |
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use the GNU C may_alias attribute if available, and fallback to naive
byte-by-byte loops if __GNUC__ is not defined.
this patch has been written to minimize changes so that history
remains reviewable; it does not attempt to bring the affected code
into a more consistent or elegant form.
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| 2018年09月23日 | fix undefined pointer comparison in memmove | Rich Felker | -1/+1 |
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the comparison must take place in the address space model as an
integer type, since comparing pointers that are not pointing into the
same array is undefined.
the subsequent d<s comparison however is valid, because it's only
reached in the case where the source and dest overlap, in which case
they are necessarily pointing to parts of the same array.
to make the comparison, use an unsigned range check for dist(s,d)>=n,
algebraically !(-n<s-d<n). subtracting n yields !(-2*n<s-d-n<0), which
mapped into unsigned modular arithmetic is !(-2*n<s-d-n) or rather
-2*n>=s-d-n.
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| 2012年09月10日 | reenable word-at-at-time copying in memmove | Rich Felker | -4/+27 |
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before restrict was added, memove called memcpy for forward copies and
used a byte-at-a-time loop for reverse copies. this was changed to
avoid invoking UB now that memcpy has an undefined copying order,
making memmove considerably slower.
performance is still rather bad, so I'll be adding asm soon.
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| 2012年09月06日 | remove dependency of memmove on memcpy direction | Rich Felker | -5/+4 |
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this commit introduces a performance regression in many uses of
memmove, which will need to be addressed before the next release. i'm
making it as a temporary measure so that the restrict patch can be
committed without invoking undefined behavior when memmove calls
memcpy with overlapping regions.
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| 2011年02月12日 | initial check-in, version 0.5.0 v0.5.0 | Rich Felker | -0/+14 |
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