Re: Use stack-allocated StringInfoData

On 11/3/25 22:32, David Rowley wrote:
> On Tue, 4 Nov 2025 at 09:20, Mats Kindahl <mats(dot)kindahl(at)gmail(dot)com> wrote:
>> This is using Coccinelle to transform the text based on a semantic patch (which is included in the patch). Unfortunately it mess with the whitespace a bit so it is necessary to run pg_intent after. I'm surprised that there are whitespace changes that should not be there, but I'll take a look.
> pgindent likely won't put back the types of changes that were made
> here. I think you're going to have to manually review anything that
> comes out of any automated tool, at least certainly until there's some
> confidence that the scripts are configured correctly. Loading extra
> work onto reviewers or committers that you could have easily done
> yourself isn't really a sustainable thing. We just lack bandwidth for
> that, plus it's bad etiquette.
>
> A few tips: It's fine to post rough patches to demonstrate ideas to
> the list, but make that clear when doing so. If your intention is that
> what you're sending gets committed, then please aim for as high a
> quality as you can. There just won't be any long-term patience for
> series of unvetted-by-human transformation patches from tools such as
> Coccinelle around here, especially so if you expect the community to
> vet them for you. I'm not saying that's what you're doing, but if you
> are, please take this advice.

Hi David,

My apologies for not being clear. I understand the situation and thank
you for the advice. I'll keep that in mind in the future.

Here is an updated patch that I checked manually for unnecessary
whitespace changes.

I also checked that "destroyStringInfo(info)" was handled correctly,
which would be replacing it with a call to "pfree(info.data)" since the
StringInfoData structure is now on the stack but the data buffer needs
to be released since this is what a call to destroyStringInfo() would do.

Removing any calls of "pfree(info)" when "info" was changed to
"StringInfoData" since it is no longer a dynamically allocated variable.
Note that in this case it is not necessary to free "info.data" since the
original code does not do that.

There is one such case affected by this patch, and there the buffer
pointer is copied to another variable and then returned. This can
probably be improved by just returning the buffer pointer directly
without intermediate assignment to a variable, but I avoided this to
make reviewing the code easier. It is easy to add this change either now
or later and should not affect the generated code except at very low
optimization levels.

I also added fixes manually inside check_publications_origin_tables,
check_publications, and fetch_relation_list. In
check_publication_origin_table three StringInfo was dynamically
allocated but not released after. In check_publications and
fetch_relation_list there were extra cases of using a dynamically
allocated StringInfo that was not necessary.

Best wishes,
Mats Kindahl