mw/com: Fix method signature to avoid copies of return type

score/mw/com/design/ipc_tracing/structural_event_field_extensions.puml

@@ -27,7 +27,6 @@ class "score::mw::com::impl::SkeletonEventBase" {
   +SkeletonEventBase(std::unique_ptr<SkeletonEventBindingBase> binding)
   +PrepareOffer(): score::Result<void>
   +PrepareStopOffer(): void
-  +UpdateSkeletonReference(SkeletonBase& base_skeleton): void
   -binding_: std::unique_ptr<SkeletonEventBindingBase>
   -tracing_data_: SkeletonEventTracing
 }

score/mw/com/design/skeleton_proxy/skeleton_binding_model.puml

@@ -40,8 +40,7 @@ abstract class "score::mw::com::impl::SkeletonBase" as SkeletonBase {
     +StopOfferService(): void
     --
     Notes:
-    SkeletonBase is moveable but not copyable. On moving, the SkeletonBase should call
-    UpdateSkeletonReference on all events and fields within its events_ and fields_ maps.
+    SkeletonBase is moveable but not copyable. On moving, the SkeletonBase updates method references.
 }
 
 class SkeletonBinding {
@@ -91,7 +90,6 @@ abstract class "score::mw::com::impl::SkeletonFieldBase" as SkeletonFieldBase {
     +SkeletonFieldBase(SkeletonBase&, std::string_view field_name, std::unique_ptr<impl::SkeletonEventBase>)
     +PrepareOffer(): Result<void>
     +PrepareStopOffer(): void
-    +UpdateSkeletonReference(SkeletonBase& base_skeleton): void
 
     -IsInitialValueSaved(): bool = 0
     -DoDeferredUpdate(): Result<void> = 0
@@ -108,7 +106,6 @@ class "score::mw::com::impl::SkeletonEventBase" as SkeletonEventBase {
     +SkeletonEventBase(std::unique_ptr<SkeletonEventBindingBase> binding)
     +PrepareOffer(): score::Result<void>
     +PrepareStopOffer(): void
-    +UpdateSkeletonReference(SkeletonBase& base_skeleton): void
 
     --
     Notes:
@@ -118,8 +115,7 @@ class "score::mw::com::impl::SkeletonEventBase" as SkeletonEventBase {
     This allows SkeletonEventBase to access the type independent methods of
     SkeletonEventBindingBase. Derived classes i.e. impl::SkeletonEvent should
     downcast binding_ to a SkeletonEventBinding<SampleType> in order to use type
-    dependent methods. On moving, the SkeletonEvent should call UpdateEvent on its
-    parent skeleton so that the parent stores its new address.
+    dependent methods.
 }
 
 class SkeletonServiceMethodBinding <InArgs, OutArgs> {

score/mw/com/design/skeleton_proxy/skeleton_proxy_binding_model.puml

@@ -55,8 +55,7 @@ abstract class "score::mw::com::impl::SkeletonBase" as ScoreMwComImplSkeletonBas
   +StopOfferService(): void
   --
   Notes:
-  SkeletonBase is moveable but not copyable. On moving, the SkeletonBase should call UpdateSkeletonReference on all
-  events and fields within its events_ and fields_ maps.
+  SkeletonBase is moveable but not copyable. On moving, the SkeletonBase updates method references.
 }
 
 abstract class "DummySkeleton\n{{generated}}" as DummySkeleton {
@@ -75,7 +74,6 @@ class "score::mw::com::impl::SkeletonEventBase" as ScoreMwComImplSkeletonEventBa
   +SkeletonEventBase(std::unique_ptr<SkeletonEventBindingBase> binding)
   +PrepareOffer(): score::Result<void>
   +PrepareStopOffer(): void
-  +UpdateSkeletonReference(SkeletonBase& base_skeleton): void
   --
   Notes:
   SkeletonEventBase is moveable but not copyable.
@@ -84,15 +82,13 @@ class "score::mw::com::impl::SkeletonEventBase" as ScoreMwComImplSkeletonEventBa
   This allows SkeletonEventBase to access the type independent methods of
   SkeletonEventBindingBase. Derived classes i.e. impl::SkeletonEvent should
   downcast binding_ to a SkeletonEventBinding<SampleType> in order to use type
-  dependent methods. On moving, the SkeletonEvent should call UpdateEvent on its
-  parent skeleton so that the parent stores its new address.
+  dependent methods.
 }
 
 class "score::mw::com::impl::SkeletonFieldBase" as ScoreMwComImplSkeletonFieldBase {
   +SkeletonFieldBase(SkeletonBase&, std::string_view field_name, std::unique_ptr<impl::SkeletonEventBase>)
   +PrepareOffer(): Result<void>
   +PrepareStopOffer(): void
-  +UpdateSkeletonReference(SkeletonBase& base_skeleton): void
   --
   #skeleton_event_dispatch_ : std::unique_ptr<impl::SkeletonEventBase>
   #skeleton_base_ : std::reference_wrapper<SkeletonBase>

score/mw/com/impl/BUILD

@@ -192,6 +192,7 @@ cc_library(
     deps = [
         ":data_type_meta_info",
         ":generic_skeleton_event_binding",
+        ":reference_to_moveable",
         ":skeleton_base",
         ":skeleton_event_base",
         ":skeleton_event_binding",
@@ -243,6 +244,7 @@ cc_library(
     ],
     deps = [
         ":instance_identifier",
+        ":reference_to_moveable",
         ":runtime",
         ":skeleton_base",
         ":skeleton_event_base",
@@ -355,6 +357,7 @@ cc_library(
     ],
     deps = [
         ":flag_owner",
+        ":reference_to_moveable",
         ":skeleton_event_binding",
         "//score/mw/com/impl/tracing:skeleton_event_tracing",
         "//score/mw/com/impl/tracing:skeleton_event_tracing_data",
@@ -374,6 +377,7 @@ cc_library(
     ],
     deps = [
         ":error",
+        ":reference_to_moveable",
         ":skeleton_event_base",
         "//score/mw/com/impl/methods:skeleton_method_base",
         "@score_baselibs//score/language/futurecpp",
@@ -396,6 +400,7 @@ cc_library(
     deps = [
         ":flag_owner",
         ":instance_identifier",
+        ":reference_to_moveable",
         ":runtime",
         ":skeleton_binding",
         ":skeleton_event_base",
@@ -1064,6 +1069,18 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "reference_to_moveable",
+    srcs = [
+        "reference_to_moveable.cpp",
+    ],
+    hdrs = [
+        "reference_to_moveable.h",
+    ],
+    features = COMPILER_WARNING_FEATURES,
+    tags = ["FFI"],
+)
+
 cc_unit_test(
     name = "unit_test_runtime_single_exec",
     srcs = ["runtime_single_exec_test.cpp"],
@@ -1329,6 +1346,17 @@ cc_unit_test(
     ],
 )
 
+cc_unit_test(
+    name = "reference_to_moveable_test",
+    srcs = [
+        "reference_to_moveable_test.cpp",
+    ],
+    features = COMPILER_WARNING_FEATURES,
+    deps = [
+        ":reference_to_moveable",
+    ],
+)
+
 cc_unit_test(
     name = "unit_test",
     srcs = [

score/mw/com/impl/generic_skeleton_event.cpp

@@ -26,7 +26,7 @@ GenericSkeletonEvent::GenericSkeletonEvent(SkeletonBase& skeleton_base,
                                            std::unique_ptr<GenericSkeletonEventBinding> binding)
     : SkeletonEventBase(skeleton_base, event_name, std::move(binding))
 {
-    SkeletonBaseView{skeleton_base}.RegisterEvent(event_name, *this);
+    SkeletonBaseView{skeleton_base}.RegisterEvent(event_name, reference_to_moveable_.Get());
 
     if (binding_ != nullptr)
     {

score/mw/com/impl/methods/BUILD

@@ -28,6 +28,46 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "method_traits_checker",
+    srcs = ["method_traits_checker.cpp"],
+    hdrs = ["method_traits_checker.h"],
+    features = COMPILER_WARNING_FEATURES,
+    tags = ["FFI"],
+    visibility = [
+        "//score/mw/com:__subpackages__",
+    ],
+    deps = [
+        ":callable_traits",
+        "@score_baselibs//score/language/futurecpp",
+    ],
+)
+
+cc_library(
+    name = "callable_traits",
+    hdrs = [
+        "callable_traits.h",
+        "callable_traits_impl.h",
+    ],
+    features = COMPILER_WARNING_FEATURES,
+    tags = ["FFI"],
+    visibility = [
+        "//score/mw/com:__subpackages__",
+    ],
+    deps = [
+    ],
+)
+
+cc_unit_test(
+    name = "callable_traits_test",
+    srcs = ["callable_traits_test.cpp"],
+    deps = [
+        ":callable_traits",
+        "//score/mw/com/impl/methods/test:callable_traits_resources",
+        "@googletest//:gtest",
+    ],
+)
+
 cc_library(
     name = "proxy_method_base",
     srcs = ["proxy_method_base.cpp"],
@@ -111,6 +151,20 @@ cc_unit_test(
     ],
 )
 
+cc_unit_test(
+    name = "method_traits_checker_test",
+    srcs = ["method_traits_checker_test.cpp"],
+    features = COMPILER_WARNING_FEATURES + [
+        # These tests catch exceptions instead of using gtest EXPECT_DEATH so we disable aborts_upon_exception.
+        "-aborts_upon_exception",
+    ],
+    deps = [
+        ":method_traits_checker",
+        "@googletest//:gtest",
+        "@score_baselibs//score/language/futurecpp:futurecpp_test_support",
+    ],
+)
+
 cc_unit_test(
     name = "proxy_method_test",
     srcs = ["proxy_method_test.cpp"],
@@ -140,6 +194,7 @@ cc_library(
     deps = [
         ":skeleton_method_binding",
         "//score/mw/com/impl:method_type",
+        "//score/mw/com/impl:reference_to_moveable",
         "//score/mw/com/impl/util:type_erased_storage",
     ],
 )
@@ -154,6 +209,7 @@ cc_library(
         "//score/mw/com/impl:__subpackages__",
     ],
     deps = [
+        ":method_traits_checker",
         ":skeleton_method_binding",
         "//score/mw/com/impl:instance_identifier",
         "//score/mw/com/impl:skeleton_base",
@@ -186,6 +242,7 @@ cc_unit_test(
     deps = [
         ":skeleton_method",
         "//score/mw/com/impl/bindings/mock_binding",
+        "//score/mw/com/impl/methods/test:callable_traits_resources",
         "//score/mw/com/impl/plumbing:skeleton_method_binding_factory_mock",
         "//score/mw/com/impl/test:binding_factory_resources",
         "@score_baselibs//score/language/futurecpp",

score/mw/com/impl/methods/callable_traits.cpp

@@ -0,0 +1,13 @@
+/********************************************************************************
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+#include "score/mw/com/impl/methods/method_handler_traits.h"

score/mw/com/impl/methods/callable_traits.h

@@ -0,0 +1,79 @@
+/********************************************************************************
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ********************************************************************************/
+#ifndef SCORE_MW_COM_IMPL_METHODS_METHOD_CALLABLE_TRAITS_H
+#define SCORE_MW_COM_IMPL_METHODS_METHOD_CALLABLE_TRAITS_H
+
+#include <tuple>
+#include <type_traits>
+
+namespace score::mw::com::impl
+{
+
+/// \brief Implementation of std::remove_cvref which is only available in C++20.
+template <typename T>
+using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;
+
+/// \brief Helper struct to check if a tuple type is empty.
+template <typename T, typename = void>
+struct is_tuple_empty : std::false_type
+{
+};
+
+template <typename T>
+struct is_tuple_empty<T, std::enable_if_t<std::tuple_size_v<T> == 0U>> : std::true_type
+{
+};
+
+template <typename T>
+using is_tuple_empty_t = typename is_tuple_empty<T>::type;
+
+/// \brief Helper struct to extract the tail of a tuple (i.e. all elements except the first one) as a tuple type.
+template <typename... T>
+struct get_tuple_tail;
+
+template <typename Head, typename... Tail>
+struct get_tuple_tail<std::tuple<Head, Tail...>>
+{
+    using type = std::tuple<Tail...>;
+};
+
+template <typename T>
+using get_tuple_tail_t = typename get_tuple_tail<T>::type;
+
+/// \brief Helper struct to extract the in argument types of a callable as a tuple type in member alias `type`.
+///
+/// e.g. for a callable of type `int(const double&, int, const std::string), `get_callable_args_types<int(const
+/// double&, int, const std::string)>::type` will be `std::tuple<const double&, int, const std::string>`.
+/// Full implementation is in callable_traits_impl.h.
+template <typename T>
+struct get_callable_args_types : public get_callable_args_types<decltype(&remove_cvref_t<T>::operator())>
+{
+};
+
+/// \brief Helper struct to extract the return type of a callable as a type in member alias `type`.
+///
+/// e.g. for a callable of type `int(const double&, int, const std::string), `get_callable_return_type<int(const
+/// double&, int, const std::string)>::type` will be `int`.
+/// Full implementation is in callable_traits_impl.h.
+template <typename T>
+struct get_callable_return_type : public get_callable_return_type<decltype(&remove_cvref_t<T>::operator())>
+{
+};
+
+}  // namespace score::mw::com::impl
+
+// To avoid keeping the large number of struct specializations for different callable types in the header file, we put
+// them in a separate implementation header file.
+#include "score/mw/com/impl/methods/callable_traits_impl.h"
+
+#endif  // SCORE_MW_COM_IMPL_METHODS_METHOD_CALLABLE_TRAITS_H