From: Tom Lane <tgl@sss.pgh.pa.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
cc: Heikki Linnakangas <hlinnaka@iki.fi>, adam.warland@infor.com,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19341: REPLACE() fails to match final character when using
 nondeterministic ICU collation
In-reply-to: <9f47c6b24d6cf59002603caf19b8b3f4854176be.camel@cybertec.at>
References: <19341-1d9a22915edfec58@postgresql.org>
 <60b467ac47d5c6bbb9c21c3bdfecce8e5de60cda.camel@cybertec.at>
 <6935ea1e-cfb1-400b-9057-3d43b55d621a@iki.fi>
 <9f47c6b24d6cf59002603caf19b8b3f4854176be.camel@cybertec.at>
Comments: In-reply-to Laurenz Albe <laurenz.albe@cybertec.at>
	message dated "Tue, 02 Dec 2025 18:18:11 +0100"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <375806.1764696352.1@sss.pgh.pa.us>
Content-Transfer-Encoding: quoted-printable
Date: Tue, 02 Dec 2025 12:25:52 -0500
Message-ID: <375807.1764696352@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/375807.1764696352%40sss.pgh.pa.us>
Precedence: bulk

Laurenz Albe <laurenz.albe@cybertec.at> writes:
>>> for (const char *test_end =3D hptr; test_end <=3D haystack_end; test_e=
nd +=3D pg_mblen(test_end))

> During the last iteration of the loop, "test_end" will be equal to "hays=
tack_end",
> and the loop increment will call "pg_mblen(test_end)".

Right, clearly unsafe (and I bet valgrind would complain about it).
You need to rearrange the loop logic so that we won't attempt to
increment test_end that last time through.  Perhaps a for-loop
isn't the best way to write it.

			regards, tom lane