Subject: Re: GROUP BY DISTINCT
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Vik Fearing <vik@postgresfriends.org>,
 Georgios Kokolatos <gkokolatos@protonmail.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Erik Rijkers <er@xs4all.nl>
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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
Message-ID: <aa87b9b9-6a14-a84a-574f-e3ad2ce2504c@enterprisedb.com>
Date: Thu, 18 Mar 2021 22:14:03 +0100
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On 3/18/21 10:02 PM, Thomas Munro wrote:
> On Fri, Mar 19, 2021 at 8:27 AM Tomas Vondra
> <tomas.vondra@enterprisedb.com> wrote:
>> Hmmm, this seems to fail on lapwing with this error:
>>
>> parse_agg.c: In function 'expand_grouping_sets':
>> parse_agg.c:1851:23: error: value computed is not used
>> [-Werror=unused-value]
>> cc1: all warnings being treated as errors
>>
>> That line is this:
>>
>>     foreach_delete_current(result, cell);
>>
>> and I don't see how any of the values close by could be unused ...
>>
>> The only possibility I can think of is some sort of issue in the old-ish
>> gcc release (4.7.2).
> 
> No sure what's going on there, but data points: I tried a 32 bit build
> here (that's the other special thing about lapwing) and didn't see the
> warning.  GCC 10.  Also curculio (gcc 4.2) and snapper (gcc 4.7) are
> also showing this warning, but they don't have -Werror so they don't
> fail.  sidewinder (gcc 4.8) is not showing the warning.
> 

Thanks for the info. So it's likely related to older gcc releases. The
question is how to tweak the code to get rid of this ...


regards

-- 
Tomas Vondra
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