Horton

Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior

Ranier Vilela <ranier.vf@gmail.com>

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From: Ranier Vilela <ranier.vf@gmail.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-08-27T17:05:30Z
Lists: pgsql-hackers 
Em qui., 27 de ago. de 2020 às 13:57, Alvaro Herrera <
alvherre@2ndquadrant.com> escreveu:

> On 2020-Aug-27, Ranier Vilela wrote:
>
> > indexcmds.c (1162):
> > memcpy(part_oids, partdesc->oids, sizeof(Oid) * nparts);
>
> Looks legit, and at least per commit 13bba02271dc we do fix such things,
> even if it's useless in practice.
>
> Given that no buildfarm member has ever complained, this exercise seems
> pretty pointless.
>
Hi Álvaro,
If we are passing a null pointer in these places and it should not be done,
it is a sign that perhaps these calls should not or should not be made, and
they can be avoided.
This would eliminate undefined behavior and save some cycles?

regards,
Ranier Vilela

Commits

  1. Avoid memcpy() with a NULL source pointer and count == 0

  2. Avoid calling memcpy() with a NULL source pointer and count == 0.