[Bug tree-optimization/84050] New: missing -Warray-bounds accessing a struct array member

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84050

            Bug ID: 84050
           Summary: missing -Warray-bounds accessing a struct array member
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

GCC diagnoses tnhe out-of-bounds array index in function farray() below but
fails to diagnose the same bug in fstatic_array.

$ cat t.c && gcc -O2 -S -Wall t.c
struct A { int a[3]; };

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

  return a.a[7];   // missing -Warray-bounds
}

int farray (void)
{
  extern struct A f (void);

  struct A a = f ();

  return a.a[7];   // -Warray-bounds (good)
}

t.c: In function ‘farray’:
t.c:16:13: warning: array subscript 7 is above array bounds of ‘int[3]’
[-Warray-bounds]
   return a.a[7];   // -Warray-bounds (good)
          ~~~^~~