re PR c++/70323 (missing error on integer overflow in constexpr function result converted to bool)

	PR c++/70323

	* constexpr.c (cxx_eval_call_expression): Don't cache result if
	*overflow_p.

From-SVN: r234463

gcc/cp/ChangeLog

+2016-03-24  Jason Merrill  <jason@redhat.com>
+
+	PR c++/70323
+	* constexpr.c (cxx_eval_call_expression): Don't cache result if
+	*overflow_p.
+
 2016-03-24  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/62212

gcc/cp/constexpr.c

@@ -1448,7 +1448,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
 
       if (result == error_mark_node)
 	*non_constant_p = true;
-      if (*non_constant_p)
+      if (*non_constant_p || *overflow_p)
 	result = error_mark_node;
       else if (!result)
 	result = void_node;

gcc/testsuite/g++.dg/cpp0x/constexpr-70323a.C

+// PR c++/70323
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wall" }
+
+constexpr int overflow_if_0 (int i) { return __INT_MAX__ + !i; }
+constexpr int overflow_if_1 (int i) { return __INT_MAX__ + i; }
+
+constexpr bool i0_0 = overflow_if_0 (0);   // { dg-error "overflow in constant expression" }
+constexpr bool i0_1 = overflow_if_0 (1);
+constexpr bool i1_0 = overflow_if_1 (0);
+constexpr bool i1_1 = overflow_if_1 (1);   // { dg-error "overflow in constant expression" }