pop_n_(codegen_scope *s, int n)
{
  if ((int)s->sp-n < 0) {
    codegen_error(s, "stack pointer underflow");
  }
  s->sp-=n;
}
pop_n_(codegen_scope *s, int n)
{
  if ((int)s->sp-n < 0) {
    codegen_error(s, "stack pointer underflow");
  }
  s->sp-=n;
}