[Bug target/79671] [7 Regression] mapnik miscompilation on armv7hl since r235622

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79671

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |FIXED

--- Comment #30 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The code in comment 20 still fails even with attribute((may_alias)), so I'm not
sure how the boost code can be fixed:

inline void* operator new(__SIZE_TYPE__, void *p) { return p; }
struct A { A (float x) : f (x) {} float f; };
static_assert(sizeof(A) == sizeof(float), "");
struct B
{
  int x;
  union __attribute__((__may_alias__)) U
  {
    int a;
    char b[sizeof (float)];
  } u;
  int y;
};

__attribute__((noinline, noclone)) void
bar (B &x, B &y)
{
  if (x.x != 0)
    __builtin_abort ();
  if (x.y != 3)
    __builtin_abort ();
  if (y.x != 0)
    __builtin_abort ();
  if (y.y != 3)
    __builtin_abort ();
  float f;
  __builtin_memcpy (&f, x.u.b, sizeof (float));
  if (f != 3.5f)
    __builtin_abort ();
  __builtin_memcpy (&f, y.u.b, sizeof (float));
  if (f != 3.5f)
    __builtin_abort ();
}

__attribute__((noinline, noclone)) 
B *
baz (B &x)
{
  return &x;
}

__attribute__((noinline, noclone)) void
foo (float x)
{
  B b { 0, {}, 3 }, c;
  B *p = baz (b);
  new (b.u.b) A (x);
  c = *p;
  bar (*p, c);
}

int
main ()
{
  foo (3.5f);
}