CMake详解CMakeLists.txt

【快速查询】https://cmake.org/cmake/help/v2.8.8/cmake.html#section_Commands

1、CMake简介

　　CMake是跨平台编译工具，比make更高级一些。其编译的主要工作是生成CMakeLists.txt文件，然后根据该文件生成Makefile，最后调用make来生成可执行程序或者动态库。所以基本步骤就只有两步：（1）cmake生成CMakeLists.txt文件；（2）make执行编译工作。

　　下面一张图对比一下AutoTools与CMake的工作流程（可见CMake比较清晰简洁）：

2、CMakeLists.txt文件

详情参考：http://wiki.ros.org/catkin/CMakeLists.txt

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())  

（1）CMake Version: 
每一个 catkin CMakeLists.txt 必须以 CMake 需要的版本开始，Catkin 需要版本 2.8.3 或者更高

cmake_minimum_required(VERSION 2.8.3)  

（2）Package name: 
CMake project function 指定的文件名。

project(robot_brain)  

在 CMake script 文件中，引用 CMake package 可以使用变量 ${PROJECT_NAME}

（3）依赖功能包：

寻找需要用到的其他 CMake packages，用函数 find_package。 
至少依赖一个关于 catkin 的功能包

find_package(catkin REQUIRED)  

如果要使用 C++ 和 Boost，则需要引用 find_package 包含 Boost，并且指明 Boost 的类型，如使用 Boost threads，则：

find_package(Boost REQUIRED COMPONENTS thread)  

 （4）catkin_package() 

catkin_package() 是 catkin 支持的 CMake 宏指令。用来向编译系统指明 catkin-specific 的信息，而编译系统来生成 pkg-config and CMake files。

该函数必须用在用 add_library() or add_executable() 声明之前。 
有5个可选参数：

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  

 例如：

catkin_package(
   INCLUDE_DIRS include
   LIBRARIES ${PROJECT_NAME}
   CATKIN_DEPENDS roscpp nodelet
   DEPENDS eigen opencv)  

 （5）Specifying Build Targets

3、一个简单的CMakeLists.txt入门示例

　　外部编译：单独建立一个空目录专门用于cmake编译，便于管理编译中间文件。在空目录中用 cmake ../（CMakeLists.txt所在目录）就行了，中间文件生成在当前目录。

　　工程结构：

.
├── build
├── CMakeLists.txt
├── include
│   └── math_lib.h
└── src
    ├── main.cpp
    └── math_lib.cpp
  

# 1.cmake verson，指定cmake版本 
cmake_minimum_required(VERSION 3.4.1)
  

kuliuheng@ubuntu:~/_8GB_EXT/workspace/cpp/testCmake$ cd build/
kuliuheng@ubuntu:~/_8GB_EXT/workspace/cpp/testCmake/build$ cmake ../
-- The C compiler identification is GNU 7.4.0
-- The CXX compiler identification is GNU 7.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/kuliuheng/_8GB_EXT/workspace/cpp/testCmake/build  

file(GLOB_RECURSE header1_files "src/main/cpp/3rd/*.h")
file(GLOB_RECURSE source1_files "src/main/cpp/3rd/*.cpp")
  

# 通过add_library 可以引入三方库，通过set_target_properties 指定具体三方库的属性
add_library(plug_ins
        SHARED
        IMPORTED)
set_target_properties( plug_ins
        PROPERTIES IMPORTED_LOCATION
        ${PROJECT_SOURCE_DIR}/libs/${ANDROID_ABI}/libplug_ins_project.so)