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From: "siddhesh at gotplt dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/101397] [11 Regression] spurious warning writing to
 the result of stpcpy minus 1
Date: Tue, 26 Oct 2021 14:24:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101397

Siddhesh Poyarekar <siddhesh at gotplt dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |siddhesh at gotplt dot org

--- Comment #7 from Siddhesh Poyarekar <siddhesh at gotplt dot org> ---
(In reply to CVS Commits from comment #4)
> The master branch has been updated by Martin Sebor <msebor@gcc.gnu.org>:
>=20
> https://gcc.gnu.org/g:8bf5b49ebd2176b8c535147377381dd07fbdd643
>=20
> commit r12-2422-g8bf5b49ebd2176b8c535147377381dd07fbdd643
> Author: Martin Sebor <msebor@redhat.com>
> Date:   Tue Jul 20 13:48:20 2021 -0600
>=20
>     Correct stpcpy offset computation for -Warray-bounds et al. [PR101397=
].

This causes a crash with the following program due to an infinite recursion:

typedef __SIZE_TYPE__ size_t;

void
__attribute__ ((noinline))
foo (size_t x)
{
  struct T { char buf[64]; char buf2[64]; } t;
  char *p =3D &t.buf[8];
  char *r =3D t.buf2;
  size_t i;

  for (i =3D 0; i < x; i++)
    {
      r =3D __builtin_mempcpy (r, p, i);
      p =3D r + 1;
    }
}

$ cc1.r12-2422 -quiet -o - repro.c=20
        .file   "repro.c"
        .text
Segmentation fault (core dumped)=