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[Bug libc/12518] memcpy acts randomly (and differently) with overlapping areas


http://sourceware.org/bugzilla/show_bug.cgi?id=12518

Tudor Bosman <tudorb at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |tudorb at gmail dot com

--- Comment #28 from Tudor Bosman <tudorb at gmail dot com> ---
FYI, this bug has bitten me in a different way: memcpy() copying backwards
defeats the MADV_SEQUENTIAL flag to madvise(). A trivial file copier
implementation (mmap source, mmap destination, set MADV_SEQUENTIAL, memcpy from
source to destination) would perform much worse on machines that support SSSE3
than on machines that don't because of this bug.

(Before anyone tells me that I should copy files using read() and write(), my
actual usage pattern was more complex, but the details are irrelevant.)

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