Fix PR c++/68831 (superfluous -Waddress warning for C++ delete)

gcc/cp/ChangeLog:

	PR c++/68831
	* init.c (build_delete): Use a warning sentinel to disable
	-Waddress warnings when building the conditional that tests
	if the operand is NULL.

gcc/testsuite/ChangeLog:

	PR c++/68831
	* g++.dg/pr68831.C: New test.

From-SVN: r231798

gcc/cp/ChangeLog

+2015-12-18  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/68831
+	* init.c (build_delete): Use a warning sentinel to disable
+	-Waddress warnings when building the conditional that tests
+	if the operand is NULL.
+
 2015-12-17  Jason Merrill  <jason@redhat.com>
 
 	PR c++/67550

gcc/cp/init.c

@@ -4449,6 +4449,7 @@ build_delete (tree otype, tree addr, special_function_kind auto_delete,
       else
 	{
 	  /* Handle deleting a null pointer.  */
+	  warning_sentinel s (warn_address);
 	  ifexp = fold (cp_build_binary_op (input_location,
 					    NE_EXPR, addr, nullptr_node,
 					    complain));

gcc/testsuite/ChangeLog

+2015-12-18  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/68831
+	* g++.dg/pr68831.C: New test.
+
 2015-12-17  Jeff Law  <law@redhat.com>
 
 	* gcc.dg/tree-ssa/split-path-1.c: Explicitly ask for path

gcc/testsuite/g++.dg/pr68831.C

+// PR c++/68831
+// { dg-options "-Waddress" }
+
+class DenseMap {
+public:
+  ~DenseMap();
+};
+extern const DenseMap &GCMap;
+void foo() { delete &GCMap; }