# 3.使用CMakeLists.txt编译ROS2节点

虽然通过make调用Makefile编译代码非常的方便，但是还是需要我们手写gcc指令来编译，那有没有什么办法可以自动生成Makefile呢？

答案是有的，那就是cmake工具。

**cmake通过调用CMakeLists.txt直接生成Makefile。**

## 1.安装Cmake

```shell
sudo apt install cmake
```

## 2.新建CMakeLists.txt

在`d2lros2/d2lros2/chapt2/basic`新建`CMakeLists.txt`，输入下面内容。

```cmake
cmake_minimum_required(VERSION 3.22)

project(first_node)

#include_directories 添加特定的头文件搜索路径 ，相当于指定g++编译器的-I参数
include_directories(/opt/ros/humble/include/rclcpp/)
include_directories(/opt/ros/humble/include/rcl/)
include_directories(/opt/ros/humble/include/rcutils/)
include_directories(/opt/ros/humble/include/rcl_yaml_param_parser/)
include_directories(/opt/ros/humble/include/rosidl_runtime_c/)
include_directories(/opt/ros/humble/include/rosidl_typesupport_interface/)
include_directories(/opt/ros/humble/include/rcpputils/)
include_directories(/opt/ros/humble/include/builtin_interfaces/)
include_directories(/opt/ros/humble/include/rmw/)
include_directories(/opt/ros/humble/include/rosidl_runtime_cpp/)
include_directories(/opt/ros/humble/include/tracetools/)
include_directories(/opt/ros/humble/include/rcl_interfaces/)
include_directories(/opt/ros/humble/include/libstatistics_collector/)
include_directories(/opt/ros/humble/include/statistics_msgs/)

# link_directories - 向工程添加多个特定的库文件搜索路径，相当于指定g++编译器的-L参数
link_directories(/opt/ros/humble/lib/)

# add_executable - 生成first_node可执行文件
add_executable(first_node first_ros2_node.cpp)

# target_link_libraries - 为first_node(目标) 添加需要动态链接库，相同于指定g++编译器-l参数
# 下面的语句代替 -lrclcpp -lrcutils
target_link_libraries(first_node rclcpp rcutils)
```

## 3.编译代码

我们一般会创建一个新的目录，运行cmake并进行编译，这样的好处是不会显得那么乱。

```shell
mkdir build
cd build
```

创建好文件夹，接着运行cmake指令，`..`代表到上级目录找`CMakeLists.txt`。

```
cmake ..
```

运行完cmake你应该可以在build目录下看到cmake自动生成的Makefile了，接着就可以运行make指令进行编译

```
make
```

运行完上面的指令，就可以在build目录下发现`first_node`节点了。

![image-20220603143016936](3.使用CMakeLists.txt编译ROS2节点/imgs/image-20220603143016936.png)