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Potential issue with strstr on x86 with sse4.2 in glibc-2.18
- From: Allan McRae <allan at archlinux dot org>
- To: libc-alpha <libc-alpha at sourceware dot org>
- Date: Fri, 16 Aug 2013 22:16:29 +1000
- Subject: Potential issue with strstr on x86 with sse4.2 in glibc-2.18
This is more of a heads up as on first glance I suspect this is a gcc
issue rather than a glibc one.
I have had a number of reports for i686-pc-linux-gnu builds of glibc
(with gcc 4.8.1 20130725) giving a segfault in __strstr_sse42. Here is
our bugtracker link: https://bugs.archlinux.org/task/36556 . A bisect
puts indicates this commit:
http://sourceware.org/git/?p=glibc.git;a=commit;h=f1d70dad
and in particular, reverting this change in
sysdeps/x86_64/multiarch/strstr.c stops the issue:
-static inline __m128i
+static __m128i
__m128i_strloadu (const unsigned char * p, __m128i zero)
That's right... adding an inline solves the segfaults, hence why I
suspect a gcc issue. Also, compiling with -O3 instead of -O2 avoids the
issue.
Note that this code runs fine on x86_64. We only notice it on our i686
builds.
Allan