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Subject: Re: Possible replace of strncpy on xactdesc.c
From: Daniel Gustafsson <daniel@yesql.se>
In-Reply-To: 
 <CAFsReFVjinOs0tqbb1C_LgSrpemDNgA3zQembNytOfJyaktHFw@mail.gmail.com>
Date: Mon, 6 Jul 2026 16:38:37 +0200
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
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 <CAFsReFVjinOs0tqbb1C_LgSrpemDNgA3zQembNytOfJyaktHFw@mail.gmail.com>
To: =?utf-8?Q?Mario_Gonz=C3=A1lez_Troncoso?= <gonzalemario@gmail.com>
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> On 3 Jul 2026, at 05:47, Mario Gonz=C3=A1lez Troncoso =
<gonzalemario@gmail.com> wrote:

> I've been doing some research about if we could replace strncpy() in
> some code. It seems I found one and I'd like your opinion on it to
> determine if it's worth the change.
>=20
> Basically what I found and IMO it's worth the change is on file =
xactdesc.c
>=20
> diff --git a/src/backend/access/rmgrdesc/xactdesc.c
> b/src/backend/access/rmgrdesc/xactdesc.c
> index 4f53d3035cc..0f466a4c27c 100644
> --- a/src/backend/access/rmgrdesc/xactdesc.c
> +++ b/src/backend/access/rmgrdesc/xactdesc.c
> @@ -256,7 +256,7 @@ ParsePrepareRecord(uint8 info, xl_xact_prepare
> *xlrec, xl_xact_parsed_prepare *p
>        parsed->nabortstats =3D xlrec->nabortstats;
>        parsed->nmsgs =3D xlrec->ninvalmsgs;
>=20
> -       strncpy(parsed->twophase_gid, bufptr, xlrec->gidlen);
> +       strlcpy(parsed->twophase_gid, bufptr, =
sizeof(parsed->twophase_gid));
>        bufptr +=3D MAXALIGN(xlrec->gidlen);

As a general rule it's a good idea to replace strncpy with strlcpy.

> The other functions that are inside the file already use strlcpy() so
> maybe the use of current strncpy() on xactdesc.c is just code that
> comes from the refactor itself.

It was introduced in 1eb6d6527aae in twophase.c and then moved to =
xaxtdesc.c in
the above mentioned commit.

> I'll send a proper patch once some feedback is received but at least
> it's compiling and passing local tests.

Sounds good, please send a patch.

--
Daniel Gustafsson