re PR c++/51494 (Legal program rejection - capturing "this" when using static method inside lambda)

	PR c++/51494
	PR c++/51884
	PR c++/56222
	* tree.c (maybe_dummy_object): Don't capture 'this'.
	* semantics.c (maybe_resolve_dummy): New.
	(finish_non_static_data_member): Use it.
	(finish_qualified_id_expr): Don't test is_dummy_object.
	* cp-tree.h: Declare maybe_resolve_dummy.
	* call.c (build_new_method_call_1): Use it.

From-SVN: r196549

gcc/cp/ChangeLog

 2013-03-08  Jason Merrill  <jason@redhat.com>
 
+	PR c++/51494
+	PR c++/51884
+	PR c++/56222
+	* tree.c (maybe_dummy_object): Don't capture 'this'.
+	* semantics.c (maybe_resolve_dummy): New.
+	(finish_non_static_data_member): Use it.
+	(finish_qualified_id_expr): Don't test is_dummy_object.
+	* cp-tree.h: Declare maybe_resolve_dummy.
+	* call.c (build_new_method_call_1): Use it.
+
 	PR c++/56567
 	* semantics.c (apply_deduced_return_type): Don't allow returning
 	std::initializer_list.

gcc/cp/call.c

@@ -7627,6 +7627,7 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
       else
 	{
 	  fn = cand->fn;
+	  call = NULL_TREE;
 
 	  if (!(flags & LOOKUP_NONVIRTUAL)
 	      && DECL_PURE_VIRTUAL_P (fn)
@@ -7644,12 +7645,26 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
 	  if (TREE_CODE (TREE_TYPE (fn)) == METHOD_TYPE
 	      && is_dummy_object (instance_ptr))
 	    {
-	      if (complain & tf_error)
-		error ("cannot call member function %qD without object",
-		       fn);
-	      call = error_mark_node;
+	      instance = maybe_resolve_dummy (instance);
+	      if (instance == error_mark_node)
+		call = error_mark_node;
+	      else if (!is_dummy_object (instance))
+		{
+		  /* We captured 'this' in the current lambda now that
+		     we know we really need it.  */
+		  instance_ptr = build_this (instance);
+		  cand->first_arg = instance_ptr;
+		}
+	      else
+		{
+		  if (complain & tf_error)
+		    error ("cannot call member function %qD without object",
+			   fn);
+		  call = error_mark_node;
+		}
 	    }
-	  else
+
+	  if (call != error_mark_node)
 	    {
 	      /* Optimize away vtable lookup if we know that this
 		 function can't be overridden.  We need to check if

gcc/cp/cp-tree.h

@@ -5722,6 +5722,7 @@ extern bool is_capture_proxy			(tree);
 extern bool is_normal_capture_proxy             (tree);
 extern void register_capture_members		(tree);
 extern tree lambda_expr_this_capture            (tree);
+extern tree maybe_resolve_dummy			(tree);
 extern tree nonlambda_method_basetype		(void);
 extern void maybe_add_lambda_conv_op            (tree);
 extern bool is_lambda_ignored_entity            (tree);

gcc/cp/semantics.c

@@ -1544,6 +1544,7 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
       object = maybe_dummy_object (scope, NULL);
     }
 
+  object = maybe_resolve_dummy (object);
   if (object == error_mark_node)
     return error_mark_node;
 
@@ -1778,15 +1779,14 @@ finish_qualified_id_expr (tree qualifying_class,
     }
   else if (BASELINK_P (expr) && !processing_template_decl)
     {
-      tree ob;
-
       /* See if any of the functions are non-static members.  */
       /* If so, the expression may be relative to 'this'.  */
       if (!shared_member_p (expr)
-	  && (ob = maybe_dummy_object (qualifying_class, NULL),
-	      !is_dummy_object (ob)))
+	  && current_class_ptr
+	  && DERIVED_FROM_P (qualifying_class,
+			     current_nonlambda_class_type ()))
 	expr = (build_class_member_access_expr
-		(ob,
+		(maybe_dummy_object (qualifying_class, NULL),
 		 expr,
 		 BASELINK_ACCESS_BINFO (expr),
 		 /*preserve_reference=*/false,
@@ -9534,6 +9534,34 @@ lambda_expr_this_capture (tree lambda)
   return result;
 }
 
+/* We don't want to capture 'this' until we know we need it, i.e. after
+   overload resolution has chosen a non-static member function.  At that
+   point we call this function to turn a dummy object into a use of the
+   'this' capture.  */
+
+tree
+maybe_resolve_dummy (tree object)
+{
+  if (!is_dummy_object (object))
+    return object;
+
+  tree type = TYPE_MAIN_VARIANT (TREE_TYPE (object));
+  gcc_assert (TREE_CODE (type) != POINTER_TYPE);
+
+  if (type != current_class_type
+      && current_class_type
+      && LAMBDA_TYPE_P (current_class_type))
+    {
+      /* In a lambda, need to go through 'this' capture.  */
+      tree lam = CLASSTYPE_LAMBDA_EXPR (current_class_type);
+      tree cap = lambda_expr_this_capture (lam);
+      object = build_x_indirect_ref (EXPR_LOCATION (object), cap,
+				     RO_NULL, tf_warning_or_error);
+    }
+
+  return object;
+}
+
 /* Returns the method basetype of the innermost non-lambda function, or
    NULL_TREE if none.  */
 

gcc/cp/tree.c

@@ -2863,13 +2863,6 @@ maybe_dummy_object (tree type, tree* binfop)
       && (same_type_ignoring_top_level_qualifiers_p
 	  (TREE_TYPE (current_class_ref), context)))
     decl = current_class_ref;
-  else if (current != current_class_type
-	   && context == nonlambda_method_basetype ())
-    /* In a lambda, need to go through 'this' capture.  */
-    decl = (build_x_indirect_ref
-	    (input_location, (lambda_expr_this_capture
-			      (CLASSTYPE_LAMBDA_EXPR (current_class_type))),
-	     RO_NULL, tf_warning_or_error));
   else
     decl = build_dummy_object (context);
 

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this11.C

+// PR c++/51494, c++/56222
+// Uses of static members and creating pointers to members aren't odr-uses
+// of 'this'.
+// { dg-do compile { target c++11 } }
+
+struct A
+{
+  static void f() {}
+  static int i;
+  int j;
+  void f(int);
+
+  void foo()
+  {
+    [] () {
+      ++i;
+      f();
+      &A::j;
+      (void(*)())&A::f;
+    };
+  }
+};