Re: Small patch to improve safety of utf8_to_unicode().

> On Jun 24, 2026, at 13:45, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
>
> On Mon, 2026-06-22 at 19:02 -0700, Jeff Davis wrote:
>> v4 attached.
>
> v5 attached.
>
> There's an extra patch 0002 to fix a logic bug when handling final
> sigma (only affects the builtin pg_unicode_fast locale), which I think
> should be backported to 18.
>
> Also added tests.
>
> Regards,
> Jeff Davis
>
> <v5-0001-unicode_case.c-defend-against-invalid-UTF8.patch><v5-0002-pg_unicode_fast-fix-final-sigma-logic.patch><v5-0003-unicode_case.c-change-API-to-signal-UTF8-decoding.patch><v5-0004-Validating-iterator-friendly-UTF8-encoder-decoder.patch><v5-0005-unicode_case.c-use-new-utf8encode-utf8decode-APIs.patch>

There is a compile warning against pg_wchar.h in 0004:
```
../../../src/include/mb/pg_wchar.h:523:11: warning: variable 'codepoint' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
523 | else if (nbytes == 4)
| ^~~~~~~~~~~
../../../src/include/mb/pg_wchar.h:540:16: note: uninitialized use occurs here
540 | *pcodepoint = codepoint;
| ^~~~~~~~~
../../../src/include/mb/pg_wchar.h:523:7: note: remove the 'if' if its condition is always true
523 | else if (nbytes == 4)
| ^~~~~~~~~~~~~~~~
524 | {
../../../src/include/mb/pg_wchar.h:469:20: note: initialize the variable 'codepoint' to silence this warning
469 | char32_t codepoint;
| ^
| = 0
1 warning generated.
```

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/