Re: [RFC/PATCH] ignore memcmp() overreading in bsearch() callback

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 15, 2013, 16:55 UTC
Message-ID: <7vmwwa4c8r.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20130115155043.GA21815@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 10 quoted lines

> On Mon, Jan 14, 2013 at 03:36:21PM -0800, Junio C Hamano wrote:
>
>> It appears that memcmp() uses the usual "one word at a time"
>> comparison and triggers valgrind in a callback of bsearch() used in
>> the refname search.  I can easily trigger problems in any script
>> with test_commit (e.g. "sh t0101-at-syntax.sh --valgrind -i -v")
>> without this suppression.
>
> Out of curiosity, what platform do you see this on? I can't reproduce on
> glibc.

    Debian GNU/Linux 6.0.6 (squeeze), on Linux 2.6.32-5-amd64.
    libc-bin              2.11.3-4
    valgrind-3.6.0.SVN-Debian
    gcc                   4:4.4.5-1

Show 20 quoted lines

>> diff --git a/t/valgrind/default.supp b/t/valgrind/default.supp
>> index 0a6724f..032332f 100644
>> --- a/t/valgrind/default.supp
>> +++ b/t/valgrind/default.supp
>> @@ -49,3 +49,11 @@
>>  	Memcheck:Addr4
>>  	fun:copy_ref
>>  }
>> +
>> +{
>> +	ignore-memcmp-reading-too-much-in-bsearch-callback
>> +	Memcheck:Addr4
>> +	fun:ref_entry_cmp_sslice
>> +	fun:bsearch
>> +	fun:search_ref_dir
>> +}
>
> Given that it is valgrind-clean on my platform, and reading the code I
> don't see any problems, I think it probably is a false positive, and
> this suppression makes sense.

Thanks for a sanity check.