6.18-ROS Catkin Build System

参考

Catkin Documentation
ROS Wiki
**推荐一本书：《深入理解软件构建系统》

前言

• 是基于CMake，使用一系列CMake 宏制作而成的ROS构造系统

CMakeLists

综述

• 此文件是CMake 构造系统的输入文件，构造描述文件记录了代码如何构建以及如何安装，catkin 构建系统基于CMakeLists，但是也添加了额外的不多的约束

总体结构（严格按照顺序）

1. Required CMake Version (cmake_minimum_required)
2. Package Name (project())
3. Find other CMake/Catkin packages needed for build (find_package())
4. Message/Service/Action Generators(add_message_files(),add_service_files(),add_action_files())
5. Invoke message/service/action generation (generate_messages())
6. Specify package build info export (catkin_package())
7. Libraries/Executables to build (add_library()/add_executable()/target_link_libraries())
8. Tests to build (catkin_add_gtest())
9. Install rules (install())

find_package()思想

• CMake中的find模块的作用在于自动寻找已经存在的软件组件，这里的组件概念对应于ROS中的包的概念。如find_package(catkin REQUIRED COMPONENTS nodelet)。意思是，寻找catkin库中的nodelet组件，在这个语句中不能添加运行时依赖
• 问题来了，为什么Catkin是一个大库，ROS包是一个组件呢？其实官方文档说了，你可以可以这么写find_package(catkin REQUIRED);find_package(nodelet REQUIRED)，因为使用catkin编译，必须包含catkin包，然后你再包含nodelet包，但是这样也太不方便了。所以原因就是要方便，当然也不是方便这么一点点，还有关于环境变量。

  • Catkin packages are not really components of catkin. Rather the components feature of CMake was utilized in the design of catkin to save you significant typing time.
  • For catkin packages,if you find_package them as components of catkin,this is advantageous as a single set of environment variables is created with the catkin_ prefix.

• 注意：boost不是catkin组件哦

catkin_package()思想

• 是一个CMake 宏，用来明确catkin构建系统信息，这些信息用来生成pkg-config和CMake文件

• This function must be called before declaring any targets with add_library() or add_executable(). The function has 5 optional arguments:
  ```
  INCLUDE_DIRS - The exported include paths (i.e. cflags) for the package
  LIBRARIES - The exported libraries from the project
  CATKIN_DEPENDS - Other catkin projects that this project depends on
  DEPENDS - Non-catkin CMake projects that this project depends on
  CFG_EXTRAS - Additional configuration options

#### 关于标的的构建选项
* 自定义输出目录。
> ```
set_target_properties(python_module_library  PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_PYTHON_DESTINATION})

• 包含目录和库，创建可执行文件和库文件
  完全是CMake知识

消息，服务和动作

• 一句话，先add_service_files()，再generate_messgaes()，可谓是一键创造消息服务动作

  Messages (.msg),services (.srv),and actions (.action) files in ROS require a special preprocessor build step before being built and used by ROS packages. The point of these macros is to generate programming language-specific files so that one can utilize messages,services,and actions in their programming language of choice. The build system will generate bindings using all available generators (e.g. gencpp,genpy,genlisp,etc).

一系列注意事项（懒得翻译了）

• These macros must come BEFORE the catkin_package() macro in order for generation to work correctly.
• Your catkin_package() macro must have a CATKIN_DEPENDS dependency on message_runtime.
• You must use find_package() for the package message_generation,either alone or as a component of catkin
• Your package.xml file must contain a build dependency on message_generation and a runtime dependency on message_runtime. This is not necessary if the dependencies are pulled in transitively from other packages.
• If you have a package which builds messages and/or services as well as executables that use them,you need to create an explicit dependency on the automatically-generated message target so that they are built in the correct order. (some_target is the name of the target set by add_executable()):

单元测试

catkin_add_gtest(myUnitTest test/utest.cpp)

安装（略）

Package.xml

使用XML语言设置依赖（略）

• 实际上就是使用标记语言说明本包的基本情况
• 设置本包为Metapackages

<export>
   <metapackage />
 </export>

cmake_minimum_required(VERSION 2.8.3)
project(<PACKAGE_NAME>)
find_package(catkin REQUIRED)
catkin_metapackage()

专题：消息，服务，重配置的构造描述文件

• 只有一个包或节点是消息，服务，动作的提供者时，在构造描述文件中才需要添加相应的描述语句，如果是接受者，那么不需要提供。

  请比较rosaria和rosaria_client构造描述文件的区别

• 当需要使用到新的消息和服务类型时，才需要再构造描述文件中添加add语句
• 通过包含其他含有std_msgs的包，如rosaria，也可以间接包含std_msgs
• 嘛的，官方例程建立消息和服务都还要add_dependencies()，但是rosaria中没有这么多废话
• 消息和服务的构造描述文件

find_package(catkin REQUIRED COMPONENTS   roscpp   rospy   std_msgs   message_generation)
catkin_package(  ...  CATKIN_DEPENDS message_runtime ...  ...)
generate_messages(
#   DEPENDENCIES
#   std_msgs
)

<build_depend>message_generation</build_depend>
<run_depend>message_runtime</run_depend>

• 为什么有add_msgs()，add_srvs()，而只有generate_messages()，没有generate_srvs()等？因为服务和参数重配置本质上都是基于msg消息机制，多说一句，消息机制是建立在XMLRPC远程过程调用机制上的，进而建立在TCP/IP网络协议上

  《UNIX网络编程：进程间通信》
  重配置的构造描述文件

实例：解决zsDoor模块缺失问题

查看stereo_wall_detection的CMakeLists.txt