Does TYPE_MAX_VALUE (size_type_node) overflow?

[Florian Weimer]

I get strange warnings when I do arithmetic involving TYPE_MAX_VALUE
(size_type_node), in particular this code:

/* Multiplies MUL1 with MUL2, and adds ADD.  Returns (size_t)-1 if the
   result cannot be be represented as a size_t value.  If ADD is
   null_tree, treat it as a zero constant.
 */
tree
build_size_mult_saturated (tree mul1, tree mul2, tree add)
{
  tree max_mul1, result;
  max_mul1 = TYPE_MAX_VALUE (size_type_node);
  if (add != NULL_TREE)
    max_mul1 = size_binop(MINUS_EXPR, max_mul1, add);
  max_mul1 = size_binop(TRUNC_DIV_EXPR, max_mul1, mul2);
  result = size_binop (MULT_EXPR, mul1, mul2);
  if (add != NULL_TREE)
    result = size_binop (PLUS_EXPR, result, add);
  return build3 (COND_EXPR, sizetype,
                 build2 (EQ_EXPR, sizetype, mul2, size_zero_node),
                 add == NULL_TREE ? size_zero_node : add,
                 build3 (COND_EXPR, sizetype,
                         build2 (LE_EXPR, sizetype, mul1, max_mul1),
                         result, TYPE_MAX_VALUE (size_type_node)));
}

Is size_type_node really signed, and does TYPE_MAX_VALUE
(size_type_node) lie outside the representable range?  Is there an
easy way to get a GCC type closely matching size_t in C++?