gcc/testsuite/gcc.dg/c23-attr-fallthrough-1.c

/* Test C23 attribute syntax.  Valid use of fallthrough attribute.  */
/* { dg-do compile } */
/* { dg-options "-std=c23 -pedantic-errors -Wextra" } */

int
f (int a, int c)
{
  int b = 2;
  switch (a)
    {
    case 1:
      b = 1; /* { dg-warning "may fall through" } */
    case 2:
      b = 2;
      [[fallthrough]];
    case 3:
      b += 7;
      break;
    case 4:
      b = 5;
      [[__fallthrough__]];
    case 5:
      b += 1;
      break;
    case 6:
      if (c == 2)
	{
	  [[fallthrough]];
	}
      else
	{
	  [[fallthrough]];
	}
    case 7:
      b += 3;
      [[fallthrough]];
    default:
      b += 8;
      break;
    }
  return b;
}