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Message-ID: <4696ADEA.1040804@enterprisedb.com>
Date: Thu, 12 Jul 2007 23:40:42 +0100
From: Heikki Linnakangas <heikki@enterprisedb.com>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: Alvaro Herrera <alvherre@commandprompt.com>,
	Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: compiler warnings on the buildfarm
References: <46962BBD.5000108@kaltenbrunner.cc>
	<17428.1184249229@sss.pgh.pa.us>
	<469653BA.2040004@kaltenbrunner.cc>
	<20070712211918.GD22973@alvh.no-ip.org>
	<46969C98.60207@enterprisedb.com>
	<20070712213806.GE22973@alvh.no-ip.org>
	<4696A5F1.3010103@enterprisedb.com>
	<12639.1184279380@sss.pgh.pa.us>
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Tom Lane wrote:
> Heikki Linnakangas <heikki@enterprisedb.com> writes:
>> Hmm. It looks like I get that warning on my laptop as well. I tracked it 
>> down to these two places:
> 
>> Line 209:
>>> while (ptr - GETARR(trg) < ARRNELEM(trg))
>>> {
>>> 	text	   *item = (text *) palloc(VARHDRSZ + 3);
>>> 	
>>> 	SET_VARSIZE(item, VARHDRSZ + 3);
>>> 	CPTRGM(VARDATA(item), ptr);
>>>>> 	d[ptr - GETARR(trg)] = PointerGetDatum(item);
>>> 	ptr++;
>>> }
> 
> I'll betcha the compiler is trying to optimize the repeated calculations
> of "ptr - GETARR(trg)" into a separate variable that it increments along
> with ptr.  Maybe it is getting it wrong, or maybe the assembler is just
> confused.  Does the warning go away if you dial down the -O level?

Yes, I don't get it with -O1 or -O0.

$ gcc --version
gcc (GCC) 4.1.2 20061028 (prerelease) (Debian 4.1.1-19)

Hmm. Prerelease? This version came from debian/testing.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com