Added support for free functions and std::bind

rclcpp/include/rclcpp/function_traits.hpp

@@ -78,7 +78,7 @@ template<typename ReturnTypeT, typename ... Args>
 struct function_traits<ReturnTypeT (*)(Args ...)>: function_traits<ReturnTypeT(Args ...)>
 {};
 
-// std::bind
+// std::bind for object methods
 template<typename ClassT, typename ReturnTypeT, typename ... Args, typename ... FArgs>
 #if defined _LIBCPP_VERSION  // libc++ (Clang)
 struct function_traits<std::__1::__bind<ReturnTypeT (ClassT::*)(Args ...), FArgs ...>>
@@ -88,6 +88,22 @@ struct function_traits<std::_Bind<std::_Mem_fn<ReturnTypeT (ClassT::*)(Args ...)
 struct function_traits<
   std::_Binder<std::_Unforced, ReturnTypeT(__cdecl ClassT::*)(Args ...), FArgs ...>
 >
+#else
+#error "Unsupported C++ compiler / standard library"
+#endif
+  : function_traits<ReturnTypeT(Args ...)>
+{};
+
+// std::bind for free functions
+template<typename ReturnTypeT, typename ... Args, typename ... FArgs>
+#if defined _LIBCPP_VERSION  // libc++ (Clang)
+struct function_traits<std::__1::__bind<ReturnTypeT( &)(Args ...), FArgs ...>>
+#elif defined __GLIBCXX__  // glibc++ (GNU C++)
+struct function_traits<std::_Bind<ReturnTypeT(*(FArgs ...))(Args ...)>>
+#elif defined _MSC_VER  // MS Visual Studio
+struct function_traits<std::_Binder<std::_Unforced, ReturnTypeT(__cdecl &)(Args ...), FArgs ...>>
+#else
+#error "Unsupported C++ compiler / standard library"
 #endif
   : function_traits<ReturnTypeT(Args ...)>
 {};

rclcpp/test/test_function_traits.cpp

@@ -74,11 +74,25 @@ struct FunctionObjectOneIntOneChar
 
 struct ObjectMember
 {
-  int callback(bool a)
+  int callback_one_bool(bool a)
   {
     (void)a;
     return 7;
   }
+
+  int callback_two_bools(bool a, bool b)
+  {
+    (void)a;
+    (void)b;
+    return 8;
+  }
+
+  int callback_one_bool_one_float(bool a, float b)
+  {
+    (void)a;
+    (void)b;
+    return 9;
+  }
 };
 
 template<
@@ -371,13 +385,91 @@ TEST(TestFunctionTraits, argument_types) {
 
   ObjectMember object_member;
 
-  auto bind_one_bool = std::bind(&ObjectMember::callback, &object_member, std::placeholders::_1);
+  auto bind_one_bool = std::bind(
+    &ObjectMember::callback_one_bool, &object_member, std::placeholders::_1);
 
   static_assert(
     std::is_same<
       bool,
       rclcpp::function_traits::function_traits<decltype(bind_one_bool)>::template argument_type<0>
     >::value, "Functor accepts a bool as first argument");
+
+  auto bind_two_bools = std::bind(
+    &ObjectMember::callback_two_bools, &object_member, std::placeholders::_1,
+    std::placeholders::_2);
+
+  static_assert(
+    std::is_same<
+      bool,
+      rclcpp::function_traits::function_traits<decltype(bind_two_bools)>::template argument_type<0>
+    >::value, "Functor accepts a bool as first argument");
+
+  static_assert(
+    std::is_same<
+      bool,
+      rclcpp::function_traits::function_traits<decltype(bind_two_bools)>::template argument_type<1>
+    >::value, "Functor accepts a bool as second argument");
+
+  auto bind_one_bool_one_float = std::bind(
+    &ObjectMember::callback_one_bool_one_float, &object_member, std::placeholders::_1,
+    std::placeholders::_2);
+
+  static_assert(
+    std::is_same<
+      bool,
+      rclcpp::function_traits::function_traits<
+        decltype(bind_one_bool_one_float)
+      >::template argument_type<0>
+    >::value, "Functor accepts a bool as first argument");
+
+  static_assert(
+    std::is_same<
+      float,
+      rclcpp::function_traits::function_traits<
+        decltype(bind_one_bool_one_float)
+      >::template argument_type<1>
+    >::value, "Functor accepts a float as second argument");
+
+  auto bind_one_int = std::bind(func_one_int, std::placeholders::_1);
+
+  static_assert(
+    std::is_same<
+      int,
+      rclcpp::function_traits::function_traits<decltype(bind_one_int)>::template argument_type<0>
+    >::value, "Functor accepts an int as first argument");
+
+  auto bind_two_ints = std::bind(func_two_ints, std::placeholders::_1, std::placeholders::_2);
+
+  static_assert(
+    std::is_same<
+      int,
+      rclcpp::function_traits::function_traits<decltype(bind_two_ints)>::template argument_type<0>
+    >::value, "Functor accepts an int as first argument");
+
+  static_assert(
+    std::is_same<
+      int,
+      rclcpp::function_traits::function_traits<decltype(bind_two_ints)>::template argument_type<1>
+    >::value, "Functor accepts an int as second argument");
+
+  auto bind_one_int_one_char = std::bind(
+    func_one_int_one_char, std::placeholders::_1, std::placeholders::_2);
+
+  static_assert(
+    std::is_same<
+      int,
+      rclcpp::function_traits::function_traits<
+        decltype(bind_one_int_one_char)
+      >::template argument_type<0>
+    >::value, "Functor accepts an int as first argument");
+
+  static_assert(
+    std::is_same<
+      char,
+      rclcpp::function_traits::function_traits<
+        decltype(bind_one_int_one_char)
+      >::template argument_type<1>
+    >::value, "Functor accepts a char as second argument");
 }
 
 /*
@@ -462,7 +554,8 @@ TEST(TestFunctionTraits, check_arguments) {
 
   ObjectMember object_member;
 
-  auto bind_one_bool = std::bind(&ObjectMember::callback, &object_member, std::placeholders::_1);
+  auto bind_one_bool = std::bind(
+    &ObjectMember::callback_one_bool, &object_member, std::placeholders::_1);
 
   // Test std::bind functions
   static_assert(