gcc/testsuite/gcc.dg/gnu99-const-expr-3.c

   1 /* Test for constant expressions: cases involving VLAs and typeof.  */
   2 /* Origin: Joseph Myers <joseph@codesourcery.com> */
   3 /* { dg-do compile } */
   4 /* { dg-options "-std=gnu99 -pedantic-errors" } */
   5
   6 /* It appears address constants may contain casts to variably modified
   7    types.  Whether they should be permitted was discussed in
   8    <http://groups.google.com/group/comp.std.c/msg/923eee5ab690fd98>
   9    <LV7g2Vy3ARF$Ew9Q@romana.davros.org>; since static pointers to VLAs
  10    are definitely permitted within functions and may be initialized
  11    and such initialization involves implicit conversion to a variably
  12    modified type, allowing explicit casts seems appropriate.  Thus,
  13    GCC allows them as long as the "evaluated" size expressions do not
  14    contain the various operators not permitted to be evaluated in a
  15    constant expression, and as long as the result is genuinely
  16    constant (meaning that pointer arithmetic using the size of the VLA
  17    is generally not permitted).  */
  18
  19 static int sa[100];
  20
  21 int
  22 f (int m, int n)
  23 {
  24   static int (*a1)[n] = &sa;
  25   static int (*a2)[n] = (__typeof__(int (*)[n]))sa;
  26   static int (*a3)[n] = (__typeof__(int (*)[(int){m++}]))sa; /* { dg-error "constant" } */
  27   static int (*a4)[n] = (__typeof__((int (*)[n])sa))sa;
  28   static int (*a5)[n] = (__typeof__((int (*)[m++])sa))sa; /* { dg-error "constant" } */
  29   static int (*a6)[n] = (__typeof__((int (*)[100])(int (*)[m++])sa))sa;
  30   static int (*a7)[n] = (__typeof__((int (*)[n])sa + m++))sa; /* { dg-error "constant" } */
  31   return n;
  32 }