Subject: Re: valgrind issues on Fedora 28
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>,
 pgsql-hackers@lists.postgresql.org
References: <20181106173527.omm63tiaguxft7mg@alvherre.pgsql>
 <f6577fe9-def2-7614-958f-9a8fb810f666@2ndquadrant.com>
 <23c8e539-6777-1793-0939-12e73cb98314@2ndquadrant.com>
 <9063c043-83cd-b439-a928-622a743edd2c@2ndquadrant.com>
 <16353.1544760625@sss.pgh.pa.us>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <4721dbaf-b922-9e30-e635-00f06512edac@2ndquadrant.com>
Date: Fri, 14 Dec 2018 13:49:11 +0100
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On 12/14/18 5:10 AM, Tom Lane wrote:
> Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> On 11/8/18 1:07 PM, Tomas Vondra wrote:
>>> Not sure what to do about this - maybe we should wildcard this first
>>> frame, to accept all wcsnlen variants. Opinions?
> 
>> I've committed this with the first frame wirldcarded, and backpatched it
>> all the way back to 9.4.
> 
> So I just got around to trying to do some valgrind testing for the first
> time in a couple of months, and what I find is that this patch completely
> breaks valgrind for me: it exits immediately with complaints like
> 
> ==00:00:00:00.222 14821== FATAL: in suppressions file "/home/postgres/pgsql/src/tools/valgrind.supp" near line 227:
> ==00:00:00:00.222 14821==    unknown tool suppression type
> ==00:00:00:00.222 14821== exiting now.
> 
> After a bit of hair-pulling I found that the line number report is
> a lie, and what it's really unhappy about is the "Memcheck:Addr32"
> specification on line 236.  This is not terribly surprising perhaps
> considering that "Addr32" isn't even documented on what should be
> the authoritative page:
> http://valgrind.org/docs/manual/mc-manual.html#mc-manual.suppfiles
> 

Hmm :-( FWIW the Addr32 comes directly from valgrind itself, which
explicitly suggested to add suppression like this:

    {
       <insert_a_suppression_name_here>
       Memcheck:Addr32
       fun:__wcsnlen_avx2
       fun:wcsrtombs
       fun:wcstombs
       fun:wchar2char
       fun:str_tolower
       fun:lower
       fun:DirectFunctionCall1Coll
       fun:Generic_Text_IC_like
       ...
    }

My guess is that documentation is either somewhat obsolete, or is meant
more like a general description than an exhaustive and authoritative
source of truth regarding suppressions.

> This is valgrind 3.8.1 (RHEL6's version), so not bleeding edge exactly,
> but we have very little evidence about how far back the committed patch
> works.  I'm inclined to think we can't use this solution.
> 

Fedora 28 has 3.14.0, so this seems to be due to some improvements since
3.8.1. I'm not sure how to deal with this - surely we don't want to just
revert the change because that would start generating noise again. For a
moment I thought we might wildcard the error type somehow, so that it
would accept Memcheck:* but AFAICs that is not supported.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services