libs-base/config/config.builtin_apply.c

typedef void(*apply_t)(void);	/* function pointer */
typedef union {
  char *arg_ptr;
  char arg_regs[sizeof (char*)];
} *arglist_t;			/* argument frame */

double ret_double3(int i, int j)
{
  static double d = 1.23456;
  return d;
}

double ret_double2(int i, int j)
{
  double d = 0.0 + i + j;
  return d;
}

double ret_double(int i, int j)
{
  arglist_t argframe;
  int stack_argsize;
  int reg_argsize;
  void *ret;
  void *(*imp)();
  
  imp = ret_double3;
  /* void *args = __builtin_apply_args(); */
  stack_argsize = 0;
  reg_argsize = 8;
  argframe = (arglist_t) alloca(sizeof(char*) + reg_argsize);
  if (stack_argsize)
    argframe->arg_ptr = alloca(stack_argsize);
  else
    argframe->arg_ptr = 0;

  ret = __builtin_apply(imp, argframe, 0);
  __builtin_return(ret);
}

int main()
{
  double d;

  d = ret_double3(2, 3);
  printf("got %f\n", d);
  d = ret_double(2, 3);
  printf("got %f\n", d);
  exit(0);
}