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Message-ID: <d440cf7dd4de4260849d9216986f3a1b47968837.camel@klomp.org>
Subject: Re: glibc 2.36 build failure on Fedora 36 with gcc 12
 (-Werror=use-after-free)
From: Mark Wielaard <mark@klomp.org>
To: Carlos O'Donell <carlos@redhat.com>, libc-alpha <libc-alpha@sourceware.org>
Date: Fri, 29 Jul 2022 17:52:33 +0200
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References: <ba9bccae-17db-0133-9361-c22582604eed@redhat.com>
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Hi Carlos,

On Fri, 2022-07-29 at 11:26 -0400, Carlos O'Donell via Libc-alpha
wrote:
> Just posting here for the record that I see a glibc 2.36 build
> failure
> with Fedora 36 and gcc 12.
>=20
> localealias.c: In function =E2=80=98read_alias_file=E2=80=99:
> localealias.c:335:56: error: pointer may be used after =E2=80=98realloc=
=E2=80=99 [-
> Werror=3Duse-after-free]
>   335 |                               map[i].alias +=3D new_pool -
> string_space;
>       |                                               ~~~~~~~~~^~~~~~
> ~~~~~~~~
> localealias.c:325:49: note: call to =E2=80=98realloc=E2=80=99 here
>   325 |                       char *new_pool =3D (char *) realloc
> (string_space, new_size);
>       |                                                 ^~~~~~~~~~~~~
> ~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>=20
> I'm going to review this quickly before we make the glibc release.

We aren't seeing those on the Fedora 36 buildbot or on other gcc 12
using distros:
https://builder.sourceware.org/buildbot/#/builders?tags=3Dglibc

There was a bug in earlier gcc12 releases with realloc that was fixed
by=20
https://gcc.gnu.org/r12-6712-g2f714642e574c64e1c0e093cad3de6f8accb6ec7

Maybe updating gcc might help?

Cheers,

Mark