Re: glibc 2.36 build failure on Fedora 36 with gcc 12 (-Werror=use-after-free)

[Mark Wielaard <mark@klomp.org>]

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.
> 
> localealias.c: In function ‘read_alias_file’:
> localealias.c:335:56: error: pointer may be used after ‘realloc’ [-
> Werror=use-after-free]
>   335 |                               map[i].alias += new_pool -
> string_space;
>       |                                               ~~~~~~~~~^~~~~~
> ~~~~~~~~
> localealias.c:325:49: note: call to ‘realloc’ here
>   325 |                       char *new_pool = (char *) realloc
> (string_space, new_size);
>       |                                                 ^~~~~~~~~~~~~
> ~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> 
> 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=glibc

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

Maybe updating gcc might help?

Cheers,

Mark