Comment 0 for bug 1027977

$valgrind --version
valgrind-3.7.0

When an application that uses the strstr() function from the C standard library is profiled with valgrind --tool=callgrind, the strstr() function produces false results (at least) under the following conditions:
* the string s1 to search in and the string s2 to search for are exact duplicates, that is strcmp(s1,s2)==0. s1 and s2 don't need to be pointing to the same memory object.
* the string length (excluding terminating zero) is a multiple of 16

Expected result: strstr(s1,s2) returns s1, indicating a match at the first charactor of s1
What happens: strstr(s1,s2) returns NULL, indicating no matching substring was found.

See attached minimal testcase for an example. Reproduce under Ubuntu 12.04 with the following steps:
$gcc strstrtest.c -o strstrtest
$./ strstrtest # <-- should report no errors
$valgrind --tool=callgrind ./ strstrtest # <-- should report errors for lengths multiple of 16

- The Problem does not show up under valgrind-3.6.0.SVN-Debian from Ubuntu 10.04 Lucid Lynx
- The Problem does not show up under tool=memcheck.

Some more info:
OS: Ubuntu 12.04 Precise Pangolin
$uname -a
Linux mhassert 3.2.0-26-generic #41-Ubuntu SMP Thu Jun 14 17:49:24 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux