[Bug middle-end/59741] New: Union with struct with flexible array member output incorrectly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59741

            Bug ID: 59741
           Summary: Union with struct with flexible array member output
                    incorrectly
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org

I believe this testcase will fail on -fsection-anchors targets (but haven't
verified other than eyeballing the assembly):

struct A { int a; char b[]; };
union B { struct A a; char b[sizeof (struct A) + 31]; };
union B b = { { 1, "123456789012345678901234567890" } };
union B c = { { 2, "123456789012345678901234567890" } };

__attribute__((noinline, noclone)) void
foo (int *x[2])
{
  x[0] = &b.a.a;
  x[1] = &c.a.a;
}

int
main ()
{
  int *x[2];
  foo (x);
  if (*x[0] != 1 || *x[1] != 2)
    __builtin_abort ();
  return 0;
}

Even on x86_64-linux, one can see bogus assembly:
.type c, @object
.size c, 36
c:
.long 2
.string "123456789012345678901234567890"
.zero 32
.globl b
.align 16
.type b, @object
.size b, 36
b:
.long 1
.string "123456789012345678901234567890"
.zero 32
(note, .size is correct, but the actual data for the vars much larger than
that).