re PR c++/55710 ([C++11] Linkage errors with lambdas)

	PR c++/55710
	* semantics.c (maybe_add_lambda_conv_op): Mark static thunk
	TREE_USED.

From-SVN: r196025

gcc/cp/ChangeLog

 2013-02-13  Jason Merrill  <jason@redhat.com>
 
+	PR c++/55710
+	* semantics.c (maybe_add_lambda_conv_op): Mark static thunk
+	TREE_USED.
+
 	PR c++/55879
 	* semantics.c (cxx_bind_parameters_in_call): Undo DECL_BY_REFERENCE.
 

gcc/cp/semantics.c

@@ -9559,6 +9559,8 @@ maybe_add_lambda_conv_op (tree type)
   body = begin_function_body ();
   compound_stmt = begin_compound_stmt (0);
 
+  /* decl_needed_p needs to see that it's used.  */
+  TREE_USED (statfn) = 1;
   finish_return_stmt (decay_conversion (statfn, tf_warning_or_error));
 
   finish_compound_stmt (compound_stmt);

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv7.C

+// PR c++/55710
+// { dg-do link { target c++11 } }
+
+template <class T>
+struct X {
+  static void (*code) ();
+};
+
+template <class T>
+void (*X<T>::code) () = []{};  // Line 7
+
+struct Y {
+  void (*code) () = []{} ; // Line 10
+  void operator()() { code(); }
+};
+
+int main () {
+  X<int>::code();
+  Y()();
+}