re PR c++/77591 (decltype(auto) and ternary operator allow returning local…

re PR c++/77591 (decltype(auto) and ternary operator allow returning local reference without a warning)

	PR c++/77591
	* typeck.c (maybe_warn_about_returning_address_of_local): Optimize
	whats_returned through fold_for_warn.

	* g++.dg/cpp1y/pr77591.C: New test.

From-SVN: r242924

gcc/cp/ChangeLog

+2016-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/77591
+	* typeck.c (maybe_warn_about_returning_address_of_local): Optimize
+	whats_returned through fold_for_warn.
+
 2016-11-27  Jason Merrill  <jason@redhat.com>
 
 	PR c++/77907

gcc/cp/typeck.c

@@ -8612,7 +8612,7 @@ static bool
 maybe_warn_about_returning_address_of_local (tree retval)
 {
   tree valtype = TREE_TYPE (DECL_RESULT (current_function_decl));
-  tree whats_returned = retval;
+  tree whats_returned = fold_for_warn (retval);
 
   for (;;)
     {

gcc/testsuite/ChangeLog

+2016-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/77591
+	* g++.dg/cpp1y/pr77591.C: New test.
+
 2016-11-28  David Edelsohn  <dje.gcc@gmail.com>
 
 	* gcc.dg/torture/pr78515.c: Ignore ABI extension warning.

gcc/testsuite/g++.dg/cpp1y/pr77591.C

+// PR c++/77591
+// { dg-do compile { target c++14 } }
+// { dg-options "-O0 -Wreturn-local-addr" }
+
+class A { };
+
+decltype(auto)
+foo ()
+{
+  A c;			// { dg-warning "reference to local variable 'c' returned" }
+  return (c);
+}
+
+decltype(auto)
+bar ()
+{
+  A c;			// { dg-warning "reference to local variable 'c' returned" }
+  return 1==1 ? c : c;
+}