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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/104060] [11/12 Regression]
 -Wmaybe-uninitialized false alarm on address of local array
Date: Mon, 17 Jan 2022 03:49:32 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104060

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-01-17
      Known to work|                            |10.3.0
            Summary|-Wmaybe-uninitialized false |[11/12 Regression]
                   |alarm on address of local   |-Wmaybe-uninitialized false
                   |array                       |alarm on address of local
                   |                            |array
      Known to fail|                            |11.1.0
           Keywords|                            |diagnostic
   Target Milestone|---                         |11.3

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed reduced further:
void *ptr_align (void const *ptr, unsigned long alignment);

int j (void)
{
  unsigned char j[10000];
  unsigned char *k =3D ptr_align (j, 1024);
  return !k;
}

The warning is suspect to make sure you have accessed something inside j be=
fore
the call to ptr_align but it looks like the warning just produces false
positive 100% of the time in this testcase and there is no way for the warn=
ing
to be shut up correctly..
There is no way for GCC to know what ptr_align does, GCC thinks it reads fr=
om
the first argument but it does not.

Note my recommendation to how to fix this is we should just revert this war=
ning
which was added for GCC 11 and close the original bug which asks about this
warning as won't fix.=