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Subject: Re: Small patch to improve safety of utf8_to_unicode().
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <fb7979177b7ab44d9abc2d423391de4ad9faea46.camel@j-davis.com>
Date: Wed, 24 Jun 2026 16:44:30 +0800
Cc: pgsql-hackers@postgresql.org
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To: Jeff Davis <pgsql@j-davis.com>
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> On Jun 24, 2026, at 13:45, Jeff Davis <pgsql@j-davis.com> wrote:
>=20
> On Mon, 2026-06-22 at 19:02 -0700, Jeff Davis wrote:
>> v4 attached.
>=20
> v5 attached.
>=20
> 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.
>=20
> Also added tests.
>=20
> Regards,
> Jeff Davis
>=20
> =
<v5-0001-unicode_case.c-defend-against-invalid-UTF8.patch><v5-0002-pg_unic=
ode_fast-fix-final-sigma-logic.patch><v5-0003-unicode_case.c-change-API-to=
-signal-UTF8-decoding.patch><v5-0004-Validating-iterator-friendly-UTF8-enc=
oder-decoder.patch><v5-0005-unicode_case.c-use-new-utf8encode-utf8decode-A=
PIs.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 =3D=3D 4)
      |                  ^~~~~~~~~~~
../../../src/include/mb/pg_wchar.h:540:16: note: uninitialized use =
occurs here
  540 |         *pcodepoint =3D codepoint;
      |                       ^~~~~~~~~
../../../src/include/mb/pg_wchar.h:523:7: note: remove the 'if' if its =
condition is always true
  523 |         else if (nbytes =3D=3D 4)
      |              ^~~~~~~~~~~~~~~~
  524 |         {
../../../src/include/mb/pg_wchar.h:469:20: note: initialize the variable =
'codepoint' to silence this warning
  469 |         char32_t        codepoint;
      |                                  ^
      |                                   =3D 0
1 warning generated.
```

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