On 03/17/2016 10:45 AM, Jason Merrill wrote:
On 03/16/2016 08:43 PM, Martin Sebor wrote:
@@ -3974,6 +3974,38 @@ build_vec_cmp (tree_code code, tree type,
return build3 (VEC_COND_EXPR, type, cmp, minus_one_vec, zero_vec);
}
+/* Possibly warn about an address never being NULL. */
+
+static void
+warn_for_null_address (location_t location, tree op, tsubst_flags_t
complain)
+{
...
+ if (TREE_CODE (cop) == ADDR_EXPR
+ && decl_with_nonnull_addr_p (TREE_OPERAND (cop, 0))
+ && !TREE_NO_WARNING (cop))
+ warning_at (location, OPT_Waddress, "the address of %qD will
never "
+ "be NULL", TREE_OPERAND (cop, 0));
+
+ if (CONVERT_EXPR_P (op)
+ && TREE_CODE (TREE_TYPE (TREE_OPERAND (op, 0))) ==
REFERENCE_TYPE)
+ {
+ tree inner_op = op;
+ STRIP_NOPS (inner_op);
+
+ if (DECL_P (inner_op))
+ warning_at (location, OPT_Waddress,
+ "the compiler can assume that the address of "
+ "%qD will never be NULL", inner_op);
Since I noted the subtle differences between the phrasing of
the various -Waddress warnings in the bug, I have to ask: what is
the significance of the difference between the two warnings here?
The difference is that in the second case, a reference could be bound to
a null address, but that has undefined behavior, so the compiler can
assume it won't happen.
So the first can't happen, the second could, but would be considered
undefined behavior.
jeff
