[PATCH] [tsan] Fix strcmp/strncmp interceptor return value

[Kostya Serebryany]

Alexey, could you please take a look?

The proper fix, imho, is to move the appropriate interceptors
from asan/asan_interceptors.cc to
sanitizer_common/sanitizer_common_interceptors.inc and delete the incorrect
copies from
tsan/rtl/tsan_interceptors.cc



On Thu, Jul 11, 2013 at 9:19 PM, Matthew Dempsky <matthew at dempsky.org>wrote:

> C99 says memcmp, strcmp, and strncmp return the difference of
> character values interpreted as unsigned char values.  tsan's memcmp
> interceptor already does this correctly, but strcmp and strncmp do
> not.
>
> Untested patch below.
>
> Index: tsan_interceptors.cc
> ===================================================================
> --- tsan_interceptors.cc        (revision 186094)
> +++ tsan_interceptors.cc        (working copy)
> @@ -599,7 +599,7 @@
>    }
>    MemoryAccessRange(thr, pc, (uptr)s1, len + 1, false);
>    MemoryAccessRange(thr, pc, (uptr)s2, len + 1, false);
> -  return s1[len] - s2[len];
> +  return (unsigned char)s1[len] - (unsigned char)s2[len];
>  }
>
>  TSAN_INTERCEPTOR(int, strncmp, const char *s1, const char *s2, uptr n) {
> @@ -611,7 +611,7 @@
>    }
>    MemoryAccessRange(thr, pc, (uptr)s1, len < n ? len + 1 : n, false);
>    MemoryAccessRange(thr, pc, (uptr)s2, len < n ? len + 1 : n, false);
> -  return len == n ? 0 : s1[len] - s2[len];
> +  return len == n ? 0 : (unsigned char)s1[len] - (unsigned char)s2[len];
>  }
>
>  TSAN_INTERCEPTOR(void*, memchr, void *s, int c, uptr n) {
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