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Re: Potential issue with strstr on x86 with sse4.2 in glibc-2.18

On 08/16/2013 08:16 AM, Allan McRae wrote:
> 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: .  A bisect
> puts indicates this commit:
> 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.

Thanks for the heads up.

We also just saw an i686 and gcc 4.8 inlining issue recently where
adding noinline fixed it. It might not be the same issue, but I just
wanted to add our data point. Our example is a little more complicated
though and harder to explain.


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