[Bug tree-optimization/84050] [6/7/8 Regression] missing -Warray-bounds accessing a struct array member

2018-02-13 Thread law at redhat dot com 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84050

Jeffrey A. Law  changed:

   What|Removed |Added

 CC||law at redhat dot com
   Target Milestone|6.5 |9.0

[Bug tree-optimization/84050] [6/7/8 Regression] missing -Warray-bounds accessing a struct array member

2018-01-26 Thread aldyh at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84050

Aldy Hernandez  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2018-01-26
 CC||aldyh at gcc dot gnu.org,
   ||hubicka at gcc dot gnu.org,
   ||jakub at gcc dot gnu.org
   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=84047
 Ever confirmed|0   |1

--- Comment #2 from Aldy Hernandez  ---
Confirmed.

FWIW, my patch for 84047 does not fix this PR, as VRP never sees the
problematic instruction and is not able to warn.  This is because ccp2 has
removed the instruction.

Before ccp2 we had:

fstatic_array ()
{
  static struct A a = {.a={1, 2, 3}};
  int _2;

   [local count: 1073741825]:
  _2 = a.a[7];
  return _2;
}

After ccp2 we have:

fstatic_array ()
{
  static struct A a = {.a={1, 2, 3}};

   [local count: 1073741825]:
  return 0;
}

I'm not a language lawyer, so I don't know what the semantics of undefined
behavior is.  Is returning 0 even the correct thing to do?

Though perhaps, as Jakub mentions in pr84047, maybe we should move this GCC 9?

[Bug tree-optimization/84050] [6/7/8 Regression] missing -Warray-bounds accessing a struct array member

2018-01-26 Thread rguenth at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84050

Richard Biener  changed:

   What|Removed |Added

   Target Milestone|--- |6.5

[Bug tree-optimization/84050] [6/7/8 Regression] missing -Warray-bounds accessing a struct array member

2018-01-25 Thread msebor at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84050

Martin Sebor  changed:

   What|Removed |Added

   Keywords||diagnostic
  Known to work||4.5.4
   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=83776
Summary|missing -Warray-bounds  |[6/7/8 Regression] missing
   |accessing a struct array|-Warray-bounds accessing a
   |member  |struct array member
  Known to fail||4.6.4, 4.7.4, 4.8.4, 4.9.4,
   ||5.5.0, 6.4.0, 7.2.0, 8.0

--- Comment #1 from Martin Sebor  ---
Same as in bug 83776, bisection points to r164688 committed into GCC 4.6 as the
root cause of the regression:

r164688 | hubicka | 2010-09-28 12:28:39 -0400 (Tue, 28 Sep 2010) | 5 lines

* tree-ssa-ccp.c (fold_ctor_reference): New function.
(fold_const_aggregate_ref): Use it.
* fold-const.c (canonicalize_constructor_val): Check that we don't fold
into external static.