--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/warn/Wformat-method.C	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,40 @@
+// { dg-options "-Wformat -fdiagnostics-show-caret" }
+
+class logger
+{
+public:
+  void log (const char *fmt, ...) __attribute__((format (printf, 2, 3)));
+};
+
+void test ()
+{
+  logger out;
+  out.log ("before %s after", 42); // { dg-warning "argument 3 has type 'int'" }
+  /* { dg-begin-multiline-output "" }
+   out.log ("before %s after", 42);
+                    ~^         ~~
+                     |         |
+                     char*     int
+                    %d
+   { dg-end-multiline-output "" } */
+}
+
+template <typename T>
+class logger_2
+{
+public:
+  void log (const char *fmt, ...) __attribute__((format (printf, 2, 3)));
+};
+
+void test_2 ()
+{
+  logger_2<int> out;
+  out.log ("before %s after", 42); // { dg-warning "argument 3 has type 'int'" }
+  /* { dg-begin-multiline-output "" }
+   out.log ("before %s after", 42);
+                    ~^         ~~
+                     |         |
+                     char*     int
+                    %d
+   { dg-end-multiline-output "" } */
+}