[Bug tree-optimization/91457] FAIL: g++.dg/warn/Warray-bounds-4.C -std=gnu++98 (test for warnings, line 25)

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91457

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-08-15
                 CC|                            |msebor at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed.  Here's a slightly simplified/modified test case showing the
difference in output between an x86_64 native GCC and an hppa2.0w-hp-hpux11.11
cross.  Here too compute_objsize fails because it doesn't handle the ARRAY_REF
argument in the assignment a.a[0] = 0.

$ (set -x && cat t.C && gcc -O2 -S -Wall -fdump-tree-dom3=/dev/stdout t.C &&
/build/hppa2.0w-hp-hpux11.11/gcc-svn/gcc/xgcc -B
/build/hppa2.0w-hp-hpux11.11/gcc-svn/gcc -O2 -S -Wall
-fdump-tree-dom3=/dev/stdout t.C)
+ cat t.C
struct A
{
  char n, a[0];

  A () { a[0] = 0; }
};

void f (struct A*);

void g (void)
{
  struct A a;
  f (&a);
}
+ /build/gcc-svn/gcc/xgcc -B /build/gcc-svn/gcc -O2 -S -Wall
-fdump-tree-dom3=/dev/stdout t.C
t.C: In function ‘void g()’:
t.C:5:13: warning: array subscript 0 is above array bounds of ‘char [0]’
[-Warray-bounds]
    5 |   A () { a[0] = 0; }
      |          ~~~^

;; Function g (_Z1gv, funcdef_no=3, decl_uid=2317, cgraph_uid=4,
symbol_order=3)

;; 1 loops found
;;
;; Loop 0
;;  header 0, latch 1
;;  depth 0, outer -1
;;  nodes: 0 1 2
;; 2 succs { 1 }
g ()
{
  struct A a;

  <bb 2> [local count: 1073741824]:
  a ={v} {CLOBBER};
  a.a[0] = 0;
  f (&a);
  a ={v} {CLOBBER};
  return;

}


+ /build/hppa2.0w-hp-hpux11.11/gcc-svn/gcc/xgcc -B
/build/hppa2.0w-hp-hpux11.11/gcc-svn/gcc -O2 -S -Wall
-fdump-tree-dom3=/dev/stdout t.C

;; Function g (_Z1gv, funcdef_no=3, decl_uid=1911, cgraph_uid=4,
symbol_order=3)

;; 1 loops found
;;
;; Loop 0
;;  header 0, latch 1
;;  depth 0, outer -1
;;  nodes: 0 1 2
;; 2 succs { 1 }
g ()
{
  struct A a;

  <bb 2> [local count: 1073741824]:
  MEM[(char *)&a + 1B] = 0;
  f (&a);
  a ={v} {CLOBBER};
  return;

}


In constructor ‘A::A()’,
    inlined from ‘void g()’ at t.C:12:12:
t.C:5:15: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
    5 |   A () { a[0] = 0; }
      |          ~~~~~^~~