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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/100137] [10/11 Regression] -Warray-bounds
 false positive on varying offset plus negative
Date: Mon, 19 Apr 2021 15:47:02 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100137

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot g=
nu.org

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning bug was introduced in r262893 (GCC 10).  A trivial test case is:

$ cat a.c && gcc -O2 -S -Wall a.c
int f (long i)
{
  const char *p =3D "123";
  p +=3D i;
  return p[-1];
}
a.c: In function =E2=80=98f=E2=80=99:
a.c:5:11: warning: array subscript -1 is outside array bounds of =E2=80=98c=
har[4]=E2=80=99
[-Warray-bounds]
    5 |   return p[-1];
      |          ~^~~~

This same thing is handled correctly elsewhere (e.h., -Wstringop_overflow) =
so
the ideal fix is to replace the warning code with the new pointer_query cla=
ss.=