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[Bug libc/12518] memcpy acts randomly (and differently) with overlapping areas
- From: "tudorb at gmail dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Tue, 20 Aug 2013 01:12:11 +0000
- Subject: [Bug libc/12518] memcpy acts randomly (and differently) with overlapping areas
- Auto-submitted: auto-generated
- References: <bug-12518-131 at http dot sourceware dot org/bugzilla/>
http://sourceware.org/bugzilla/show_bug.cgi?id=12518
--- Comment #30 from Tudor Bosman <tudorb at gmail dot com> ---
(In reply to Ondrej Bilka from comment #29)
> Wait, do you have overlapping source and destination areas? If so then a
> backward copy is necessary.
Backward copy is often used for non-overlapping areas as it is faster on some
Intel processors; see https://bugzilla.redhat.com/show_bug.cgi?id=638477#c99
for an explanation. I was pointing out that it also has the (unintended)
behavior of pessimizing mmap()ed file accesses.
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