add implementation of scope exit, aka scope guard

rclcpp/include/rclcpp/macros.hpp

@@ -82,6 +82,9 @@
   __RCLCPP_UNIQUE_PTR_ALIAS(__VA_ARGS__) \
   __RCLCPP_MAKE_UNIQUE_DEFINITION(__VA_ARGS__)
 
+#define RCLCPP_STRING_JOIN(arg1, arg2) RCLCPP_DO_STRING_JOIN(arg1, arg2)
+#define RCLCPP_DO_STRING_JOIN(arg1, arg2) arg1 ## arg2
+
 #define RCLCPP_INFO(Args) std::cout << Args << std::endl;
 
 #endif  // RCLCPP__MACROS_HPP_

rclcpp/src/rclcpp/scope_exit.hpp

@@ -0,0 +1,52 @@
+// Copyright 2015 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Based on: http://the-witness.net/news/2012/11/scopeexit-in-c11/
+// But I changed the lambda to include by reference rather than value, see:
+// http://the-witness.net/news/2012/11/scopeexit-in-c11/comment-page-1/#comment-86873
+
+#ifndef RCLCPP__SCOPE_EXIT_HPP_
+#define RCLCPP__SCOPE_EXIT_HPP_
+
+#include <functional>
+
+#include "rclcpp/macros.hpp"
+
+namespace rclcpp
+{
+
+template<typename Callable>
+struct ScopeExit
+{
+  explicit ScopeExit(Callable callable)
+  : callable_(callable) {}
+  ~ScopeExit() {callable_(); }
+
+private:
+  Callable callable_;
+};
+
+template<typename Callable>
+ScopeExit<Callable>
+make_scope_exit(Callable callable)
+{
+  return ScopeExit<Callable>(callable);
+}
+
+}  // namespace rclcpp
+
+#define RCLCPP_SCOPE_EXIT(code) \
+  auto RCLCPP_STRING_JOIN(scope_exit_, __LINE__) = rclcpp::make_scope_exit([&]() {code; })
+
+#endif  // RCLCPP__SCOPE_EXIT_HPP_