gcc/testsuite/gcc.dg/Wattributes-8.c

   1 /* PR middle-end/84108 - incorrect -Wattributes warning for packed/aligned
   2    conflict on struct members
   3    { dg-do compile }
   4    { dg-options "-Wall -Wattributes" } */
   5
   6 #define ATTR(list) __attribute__ (list)
   7 #define ASSERT(e) _Static_assert (e, #e)
   8
   9 /* GCC is inconsistent in how it treats attribute aligned between
  10    variable and member declarations.  Attribute aligned alone is
  11    sufficient to reduce a variable's alignment requirement but
  12    the attribute must be paired with packed to have the same
  13    effect on a member.  Worse, declaring a variable both aligned
  14    and packed emits a warning.  */
  15
  16 /* Avoid exercising this since emitting a warning for these given
  17    the requirement for members seems like a misfeature:
  18    int a ATTR ((packed, aligned (2)));   // -Wattributes
  19    int b ATTR ((aligned (2), packed));   // -Wattributes
  20    ASSERT (_Alignof (a) == 2);
  21    ASSERT (_Alignof (b) == 2);  */
  22
  23 int c ATTR ((aligned (2)));           // okay (reduces alignment)
  24 ASSERT (_Alignof (c) == 2);
  25
  26 struct {
  27   int a ATTR ((packed, aligned (2)));   /* { dg-bogus "\\\[-Wattributes" } */
  28   int b ATTR ((aligned (2), packed));   /* { dg-bogus "\\\[-Wattributes" } */
  29
  30   /* Avoid exercising this since the attribute has no effect yet
  31      there is no warning.
  32      int c ATTR ((aligned (2)));           // missing warning?  */
  33 } s;
  34
  35 ASSERT (_Alignof (s.a) == 2);
  36 ASSERT (_Alignof (s.b) == 2);
  37
  38 /* ASSERT (_Alignof (s.c) == 4); */