Re: tiny step toward threading: reduce dependence on setlocale()

On 08.08.24 22:00, Jeff Davis wrote:
> On Wed, 2024-08-07 at 22:44 +0200, Peter Eisentraut wrote:
>> But after this patch set, locale cannot be NULL anymore, so the third
>> branch is obsolete.
>
> ...
>
>> Second, there are a number of functions in like.c like the above that
>> take separate arguments like pg_locale_t locale, bool locale_is_c.
>> Because pg_locale_t now contains the locale_is_c information, these
>> can
>> be combined.
>
> I believe these patches are correct, but the reasoning is fairly
> complex:
>
> 1. Some MatchText variants are called with 0 for locale. But that's OK
> because ...
>
> 2. A MatchText variant only cares about the locale if MATCH_LOWER(t) is
> defined, and ...
>
> 3. Only one variant, SB_IMatchText() defines MATCH_LOWER(), and ...
>
> 4. SB_IMatchText() is called with a non-zero locale.
>
> All of these are a bit confusing to follow because it's generated code.
> #2 is particularly non-obvious, because "locale" is not even an
> argument of the MATCH_LOWER(t) or GETCHAR(t) macros, it's taken
> implicitly from the outer scope.
>
> I don't think your patches cause this confusion, but is there a way you
> can clarify some of this along the way?

Yes, this is also my analysis. The patch in
<https://www.postgresql.org/message-id/flat/700d2e86-bf75-4607-9cf2-f5b7802f6e88(at)eisentraut(dot)org>
would replace passing 0 with an actual locale object. The changes in
GenericMatchText() could also be applied independently so that we'd
always pass in a non-zero locale value, even if it would not be used in
some cases. I need to update that patch to cover your latest changes.
I'll see if I can propose something here that looks a bit nicer.