re PR sanitizer/67941 (calls on function pointer from a captureless lambda cause ubsan warning)

	PR c++/67941
	* lambda.c (maybe_add_lambda_conv_op): Mark _FUN as
	no_sanitize_undefined.

From-SVN: r230897

gcc/cp/ChangeLog

 2015-11-25  Jason Merrill  <jason@redhat.com>
 
+	PR c++/67941
+	* lambda.c (maybe_add_lambda_conv_op): Mark _FUN as
+	no_sanitize_undefined.
+
 	* cp-ubsan.c (cp_ubsan_instrument_vptr_p): Use
 	do_ubsan_in_current_function.
 

gcc/cp/lambda.c

@@ -1053,6 +1053,12 @@ maybe_add_lambda_conv_op (tree type)
   if (generic_lambda_p)
     fn = add_inherited_template_parms (fn, DECL_TI_TEMPLATE (callop));
 
+  /* Don't UBsan this function; we're deliberately calling op() with a null
+     object argument.  */
+  tree attrs = build_tree_list (get_identifier ("no_sanitize_undefined"),
+				NULL_TREE);
+  cplus_decl_attributes (&fn, attrs, 0);
+
   add_method (type, fn, NULL_TREE);
 
   if (nested)

gcc/testsuite/g++.dg/ubsan/null-6.C

+// PR c++/67941
+// { dg-do run { target c++11 } }
+// { dg-options -fsanitize=null }
+
+int main(){ (+[](){})(); }