Re: GROUP BY DISTINCT - Mailing list pgsql-hackers

From Tomas Vondra
Subject Re: GROUP BY DISTINCT
Date
Msg-id aa87b9b9-6a14-a84a-574f-e3ad2ce2504c@enterprisedb.com
Whole thread Raw
In response to Re: GROUP BY DISTINCT  (Thomas Munro <thomas.munro@gmail.com>)
Responses Re: GROUP BY DISTINCT
List pgsql-hackers

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
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company



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