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Date: Tue, 18 Jan 2022 17:36:59 +0100
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Subject: Re: psql - add SHOW_ALL_RESULTS option
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To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
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From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
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On 15.01.22 10:00, Fabien COELHO wrote:
>> The reason this test constantly fails on cfbot windows is a 
>> use-after-free
>> bug.
> 
> Indeed! Thanks a lot for the catch and the debug!
> 
> The ClearOrSaveResult function is quite annoying because it may or may 
> not clear the result as a side effect.
> 
> Attached v14 moves the status extraction before the possible clear. I've 
> added a couple of results = NULL after such calls in the code.

In the psql.sql test file, the test I previously added concluded with 
\set ECHO none, which was a mistake that I have now fixed.  As a result, 
the tests that you added after that point didn't show their input lines, 
which was weird and not intentional.  So the tests will now show a 
different output.

I notice that this patch has recently gained a new libpq function.  I 
gather that this is to work around the misbehaviors in libpq that we 
have discussed.  But I think if we are adding a libpq API function to 
work around a misbehavior in libpq, we might as well fix the misbehavior 
in libpq to begin with.  Adding a new public libpq function is a 
significant step, needs documentation, etc.  It would be better to do 
without.  Also, it makes one wonder how others are supposed to use this 
multiple-results API properly, if even psql can't do it without 
extending libpq.  Needs more thought.