c++ - 支持 C++14 lambda 的 ros 包

Question

好的，因为我正在使用 ROS 框架开发一个私有(private)项目，所以新的 C++14 auto lambda 功能激发了我的动力(请参阅 link 以获得更好的解释)。

我面临的问题是 ROS 框架还停留在旧时代 C++03 for it's compilation .那么，如何启用 C++14 编译支持以及如何使用 lambda 函数？

这是一个使用 lambda 函数进行测试的简单节点(在订阅者节点中):

• 发布者:

  #include <ros/ros.h>
  #include <std_msgs/String.h>
  #include <std_msgs/Int8.h>
  #include <sstream>
  
  int main(int argc, char **argv)
  {
    ros::init(argc, argv, "talker");
    ros::NodeHandle n;
    ros::Publisher string_pub = n.advertise<std_msgs::String>("chatter_string", 1000);
    ros::Publisher int_pub = n.advertise<std_msgs::Int8>("chatter_int", 1000);
    ros::Rate loop_rate(10);
  
    int count = 0;
    while (ros::ok())
    {
      std_msgs::String str_msg;
      std::stringstream ss;
      ss << "hello world ";
      str_msg.data = ss.str();
  
      std_msgs::Int8 int_msg;
      int_msg.data = count;
  
      string_pub.publish(str_msg);
      int_pub.publish(int_msg);
      ros::spinOnce();
      loop_rate.sleep();
      ++count;
    }
    return 0;
  }
  

• 订阅者:

  #include <ros/ros.h>
  #include <std_msgs/String.h>
  #include <std_msgs/Int8.h>
  
  //generic lambda to add two variables
  auto func = [](auto input) { return input + input; };
  
  void StringCallback(const std_msgs::String::ConstPtr& msg)
  {
    ROS_INFO("I heard: [%s]", func(msg->data).c_str());
  }
  
  void IntCallback(const std_msgs::Int8::ConstPtr& msg)
  {
      int result = msg->data;
    ROS_INFO("I heard: [%d]", func(result));
  }
  
  int main(int argc, char **argv)
  {
    ros::init(argc, argv, "listener");
    ros::NodeHandle n;
    ros::Subscriber string_sub = n.subscribe("chatter_string", 1000, StringCallback);
    ros::Subscriber int_sub = n.subscribe("chatter_int", 1000, IntCallback);
  
    ros::spin();
  
    return 0;
  }
  

• CMakeLists :

  cmake_minimum_required(VERSION 2.8.3)
  project(tutocpp14)
  
  find_package(catkin REQUIRED COMPONENTS
    roscpp
    rospy
    std_msgs
  )
  
  catkin_package()
  
  include_directories( ${catkin_INCLUDE_DIRS} include )
  
  add_executable(listener src/listener.cpp)
  add_executable(publisher src/publisher.cpp)
  
  target_link_libraries(listener ${catkin_LIBRARIES})
  target_link_libraries(publisher ${catkin_LIBRARIES})
  

在此配置后制作包会抛出以下错误:

tutocpp14/src/listener.cpp:10:43: error: ‘func’ was not declared in this scope
   ROS_INFO("I heard: [%s]", func(msg->data).c_str());

Answer 1

事实证明，我可以将 C++14 添加到 ROS 以进行包编译。虽然不建议发布包。

Use of C++11/C++14 features and filesystem/networking/etc... TS's (Technical Specifications) is allowed if they are checked for at configure time and equivalent functionality can be provided with the extra compiler features. Support for C++11 is now a compiler requirement, but the API of the packages included in desktop-full will not use any C++11-specific feature. External packages are encouraged to follow this guideline.

但是，我现在还不打算发表我的作品，所以，我可以让自己获得这样做的许可。

要获得对 ROS 包的 C++14 支持，我必须通过在我的 CMakelists.txt 文件中添加以下行来设置 -std=c++14 标志:

# check c++14 / c++0x
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX14)
    set(CMAKE_CXX_FLAGS "-std=c++14")
elseif(COMPILER_SUPPORTS_CXX0X)
    set(CMAKE_CXX_FLAGS "-std=c++0x")
else()
    message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++14 support. Please use a different C++ compiler.")
endif()

这将检查编译器中是否存在 C++14，如果不存在则抛出错误。现在，它就像一个魅力。

希望对您有所帮助。干杯。