re PR c++/63657 (-Wunused-variable: warning supressed by virtual dtor)

	PR c++/63657
	PR c++/38958
	* call.c (set_up_extended_ref_temp): Set TREE_USED on the reference
	if the temporary has a non-trivial destructor.
	* decl.c (poplevel): Don't look through references.

From-SVN: r217957

gcc/cp/ChangeLog

 2014-11-21  Jason Merrill  <jason@redhat.com>
 
+	PR c++/63657
+	PR c++/38958
+	* call.c (set_up_extended_ref_temp): Set TREE_USED on the reference
+	if the temporary has a non-trivial destructor.
+	* decl.c (poplevel): Don't look through references.
+
 	PR c++/63942
 	* name-lookup.c (supplement_binding_1): Override a mangling alias.
 	* mangle.c (maybe_remove_implicit_alias): New.

gcc/cp/call.c

@@ -9622,6 +9622,10 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups,
 	/* Check whether the dtor is callable.  */
 	cxx_maybe_build_cleanup (var, tf_warning_or_error);
     }
+  /* Avoid -Wunused-variable warning (c++/38958).  */
+  if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type)
+      && TREE_CODE (decl) == VAR_DECL)
+    TREE_USED (decl) = DECL_READ_P (decl) = true;
 
   *initp = init;
   return var;

gcc/cp/decl.c

@@ -638,8 +638,7 @@ poplevel (int keep, int reverse, int functionbody)
 	   push_local_binding where the list of decls returned by
 	   getdecls is built.  */
 	decl = TREE_CODE (d) == TREE_LIST ? TREE_VALUE (d) : d;
-	// See through references for improved -Wunused-variable (PR 38958).
-	tree type = non_reference (TREE_TYPE (decl));
+	tree type = TREE_TYPE (decl);
 	if (VAR_P (decl)
 	    && (! TREE_USED (decl) || !DECL_READ_P (decl))
 	    && ! DECL_IN_SYSTEM_HEADER (decl)

gcc/testsuite/g++.dg/warn/Wunused-var-22.C

+// PR c++/63657
+// { dg-options "-Wunused-variable" }
+
+class Bar
+{
+  virtual ~Bar() {}
+};
+Bar& getbar();
+void bar()
+{
+  Bar& b = getbar();		// { dg-warning "unused" }
+}