re PR c++/986 (g++ misses warning for reference on temporary that invokes undefined behaviour)

	PR c++/986
	* call.c (set_up_extended_ref_temp): Warn about references
	bound to non-static reference members.
	* init.c (perform_member_init): Pass in the member.

From-SVN: r181334

gcc/cp/ChangeLog

 2011-11-12  Jason Merrill  <jason@redhat.com>
 
+	PR c++/986
+	* call.c (set_up_extended_ref_temp): Warn about references
+	bound to non-static reference members.
+	* init.c (perform_member_init): Pass in the member.
+
 	PR c++/51060
 	* cp-gimplify.c (cp_gimplify_expr): Leave clobbers alone.
 

gcc/cp/call.c

@@ -8607,6 +8607,14 @@ set_up_extended_ref_temp (tree decl, tree expr, VEC(tree,gc) **cleanups,
   if (TREE_CODE (expr) != TARGET_EXPR)
     expr = get_target_expr (expr);
 
+  if (TREE_CODE (decl) == FIELD_DECL
+      && extra_warnings && !TREE_NO_WARNING (decl))
+    {
+      warning (OPT_Wextra, "a temporary bound to %qD only persists "
+	       "until the constructor exits", decl);
+      TREE_NO_WARNING (decl) = true;
+    }
+
   /* Recursively extend temps in this initializer.  */
   TARGET_EXPR_INITIAL (expr)
     = extend_ref_init_temps (decl, TARGET_EXPR_INITIAL (expr), cleanups);

gcc/cp/init.c

@@ -599,7 +599,7 @@ perform_member_init (tree member, tree init)
       if (init == error_mark_node)
 	return;
       /* Use 'this' as the decl, as it has the lifetime we want.  */
-      init = extend_ref_init_temps (current_class_ptr, init, &cleanups);
+      init = extend_ref_init_temps (member, init, &cleanups);
       if (TREE_CODE (type) == ARRAY_TYPE
 	  && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (type)))
 	init = build_vec_init_expr (type, init, tf_warning_or_error);

gcc/testsuite/ChangeLog

 2011-11-12  Jason Merrill  <jason@redhat.com>
 
+	PR c++/986
+	* g++.dg/warn/ref-temp1.C: New.
+
 	PR c++/51060
 	* g++.dg/opt/stack2.C: New.
 

gcc/testsuite/g++.dg/warn/ref-temp1.C

+// PR c++/986
+// { dg-options "-Wall -Wextra" }
+
+struct X { X (int); };
+
+struct Y {
+  Y ();
+  const X &x;			// note the ampersand
+};
+
+Y::Y () : x(1) {}		// { dg-warning "temporary" }