gcc/testsuite/gcc.dg/c2y-byte-alias-1.c

   1 /* { dg-do run } */
   2 /* { dg-options "-std=c2y -O2" } */
   3
   4 struct f { _Alignas(int) char buf[sizeof(int)]; };
   5 struct f2 { struct f x; };
   6 union g { _Alignas(int) char buf[sizeof(int)]; };
   7
   8 [[gnu::noinline]]
   9 int foo(struct f *p, int *q)
  10 {
  11         *q = 1;
  12         *p = (struct f){ };
  13         return *q;
  14 }
  15
  16 [[gnu::noinline]]
  17 int foo2(struct f2 *p, int *q)
  18 {
  19         *q = 1;
  20         *p = (struct f2){ };
  21         return *q;
  22 }
  23
  24 [[gnu::noinline]]
  25 int bar(union g *p, int *q)
  26 {
  27         *q = 1;
  28         *p = (union g){ };
  29         return *q;
  30 }
  31
  32
  33 int main()
  34 {
  35         struct f p;
  36         if (0 != foo(&p, (void*)&p.buf))
  37                 __builtin_abort();
  38
  39         struct f2 p2;
  40         if (0 != foo2(&p2, (void*)&p2.x.buf))
  41                 __builtin_abort();
  42
  43         union g q;
  44         if (0 != bar(&q, (void*)&q.buf))
  45                 __builtin_abort();
  46 }