re PR c++/65642 ([C++11] GCC rejects valid constant expression)

PR c++/65642
	* constexpr.c (cxx_eval_pointer_plus_expression): Call
	cxx_eval_constant_expression on the first operand.

	* g++.dg/cpp0x/constexpr-fold1.C: New test.
	* g++.dg/cpp0x/constexpr-fold2.C: New test.

From-SVN: r221843

gcc/cp/ChangeLog

@@ -1,3 +1,9 @@
+2015-04-02  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/65642
+	* constexpr.c (cxx_eval_pointer_plus_expression): Call
+	cxx_eval_constant_expression on the first operand.
+
 2015-04-01  Jason Merrill  <jason@redhat.com>
 
 	PR c++/65625

gcc/cp/constexpr.c

@@ -2933,6 +2933,9 @@ cxx_eval_pointer_plus_expression (const constexpr_ctx *ctx, tree t,
   tree op01 = TREE_OPERAND (t, 1);
   location_t loc = EXPR_LOCATION (t);
 
+  op00 = cxx_eval_constant_expression (ctx, op00, lval,
+				       non_constant_p, overflow_p);
+
   STRIP_NOPS (op00);
   if (TREE_CODE (op00) != ADDR_EXPR)
     return NULL_TREE;

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2015-04-02  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/65642
+	* g++.dg/cpp0x/constexpr-fold1.C: New test.
+	* g++.dg/cpp0x/constexpr-fold2.C: New test.
+
 2015-04-02  Jakub Jelinek  <jakub@redhat.com>
 
 	PR preprocessor/61977

gcc/testsuite/g++.dg/cpp0x/constexpr-fold1.C

@@ -0,0 +1,65 @@
+// PR c++/65642
+// { dg-do compile { target c++11 } }
+
+// Check we're able to evaluate these.
+
+#define SA(X) static_assert((X),#X)
+
+constexpr char s[] = "abc";
+constexpr int t[] = { 'a', 'b', 'c', '\0' };
+
+constexpr char
+fn1 (const char *p)
+{
+  return *(p + 1);
+}
+
+constexpr char
+fn2 (const char *p)
+{
+  return p[1];
+}
+
+constexpr int
+fn3 (const int *p)
+{
+  return *(p + 1);
+}
+
+constexpr int
+fn4 (const int *p)
+{
+  return p[1];
+}
+
+constexpr auto c1 = fn1 (&s[0]);
+constexpr auto c2 = fn1 (&s[1]);
+constexpr auto c3 = fn1 (&s[2]);
+
+SA (c1 == 'b');
+SA (c2 == 'c');
+SA (c3 == '\0');
+
+constexpr auto d1 = fn2 (&s[0]);
+constexpr auto d2 = fn2 (&s[1]);
+constexpr auto d3 = fn2 (&s[2]);
+
+SA (d1 == 'b');
+SA (d2 == 'c');
+SA (d3 == '\0');
+
+constexpr auto e1 = fn3 (&t[0]);
+constexpr auto e2 = fn3 (&t[1]);
+constexpr auto e3 = fn3 (&t[2]);
+
+SA (e1 == 'b');
+SA (e2 == 'c');
+SA (e3 == '\0');
+
+constexpr auto f1 = fn4 (&t[0]);
+constexpr auto f2 = fn4 (&t[1]);
+constexpr auto f3 = fn4 (&t[2]);
+
+SA (f1 == 'b');
+SA (f2 == 'c');
+SA (f3 == '\0');

gcc/testsuite/g++.dg/cpp0x/constexpr-fold2.C

@@ -0,0 +1,30 @@
+// PR c++/65642
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+constexpr char s[] = "abc";
+
+constexpr bool
+cmp (char const *a, char const *b)
+{
+  return a == b;
+}
+
+constexpr bool
+fn1 (const char *s)
+{
+  return cmp (s, s + 1);
+}
+
+constexpr bool
+fn2 (const char *s)
+{
+  return cmp (s + 1, s + 1);
+}
+
+constexpr auto c1 = fn1 (&s[0]);
+constexpr auto c2 = fn2 (&s[0]);
+
+SA (!c1);
+SA (c2);