《CMake构建实战》CMake 构建目标和属性
# CMake 构建目标和属性## 二进制构建目标
在构建过程中被构建的可执行文件、库文件或目标文件都可以作为二进制构建目标。
### 可执行文件目标
```cmake
add_executable(<目标名称>
[源文件...])
```
该命令会创建一个可执行文件类型的构建目标，其中第一个参数<目标名称>是必选参数，且应当在项目中唯一。
创建一个小工程实践一下。创建`008`文件夹
创建`CMakeLists.txt`
```cmake
cmake_minimum_required(VERSION 3.20)
project(myProgram)
add_executable(myProgram main.c)
add_executable(myProgramExcludedFromAll
EXCLUDE_FROM_ALL
main.c)
```
创建`main.c`
```c
#include <stdio.h>
int main() {
printf("hello world\n");
return 0;
}
```
执行命令
```bash
bruce@ubuntu:~/Documents/study/cmake/008$ touch CMakeLists.txt
bruce@ubuntu:~/Documents/study/cmake/008$ vi CMakeLists.txt
bruce@ubuntu:~/Documents/study/cmake/008$ vi main.c
bruce@ubuntu:~/Documents/study/cmake/008$ mkdir build
bruce@ubuntu:~/Documents/study/cmake/008$ cd build/
bruce@ubuntu:~/Documents/study/cmake/008/build$ cmake ..
-- The C compiler identification is GNU 13.2.0
-- The CXX compiler identification is GNU 13.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/bruce/Documents/study/cmake/008/build
bruce@ubuntu:~/Documents/study/cmake/008/build$ make
[ 50%] Building C object CMakeFiles/myProgram.dir/main.c.o
Linking C executable myProgram
Built target myProgram
bruce@ubuntu:~/Documents/study/cmake/008/build$ ./myProgram
hello world
```
### 一般库目标
一般库目标包括静态库目标、动态库目标和模块库目标。
```cmake
add_library(<目标名称> <库类型>
[<源文件>...])
```
该命令会创建一个一般库类型的构建目标，其中<目标名称>参数是必选项，且应在项目中唯一。
<库类型>参数有以下三个取值。
* STATIC
* SHARED
* MODULE
实践，创建`009`文件夹
创建 `CMakeLists.txt`
```cmake
cmake_minimum_required(VERSION 3.20)
project(mylib)
add_library(mylib lib.c)
```
创建`lib.c`
```c
int add(int a, int b) { return a+b; }
```
操作过程如下
```bash
bruce@ubuntu:~/Documents/study/cmake/009$ vi CMakeLists.txt
bruce@ubuntu:~/Documents/study/cmake/009$ ls
CMakeLists.txt
bruce@ubuntu:~/Documents/study/cmake/009$ touch lib.c
bruce@ubuntu:~/Documents/study/cmake/009$ vi lib.c
bruce@ubuntu:~/Documents/study/cmake/009$ ls
CMakeLists.txtlib.c
bruce@ubuntu:~/Documents/study/cmake/009$ mkdir build
bruce@ubuntu:~/Documents/study/cmake/009$ cd build/
bruce@ubuntu:~/Documents/study/cmake/009/build$ cmake ..
-- The C compiler identification is GNU 13.2.0
-- The CXX compiler identification is GNU 13.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/bruce/Documents/study/cmake/009/build
bruce@ubuntu:~/Documents/study/cmake/009/build$ make
[ 50%] Building C object CMakeFiles/mylib.dir/lib.c.o
Linking C static library libmylib.a
Built target mylib
bruce@ubuntu:~/Documents/study/cmake/009/build$ ls
CMakeCache.txtCMakeFilescmake_install.cmakelibmylib.aMakefile
bruce@ubuntu:~/Documents/study/cmake/009/build$
```
可以看到最后生成了 `libmylib.a`
可以看到不定义`BUILD_SHARED_LIBS`变量时，默认构建静态库。接下来试验定义`BUILD_SHARED_LIBS`
```bash
bruce@ubuntu:~/Documents/study/cmake/009/build$ cmake -DBUILD_SHARED_LIBS=ON ..
-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: /home/bruce/Documents/study/cmake/009/build
bruce@ubuntu:~/Documents/study/cmake/009/build$ cmake --build .
[ 50%] Building C object CMakeFiles/mylib.dir/lib.c.o
Linking C shared library libmylib.so
Built target mylib
bruce@ubuntu:~/Documents/study/cmake/009/build$ ls
CMakeCache.txtCMakeFilescmake_install.cmakelibmylib.alibmylib.soMakefile
bruce@ubuntu:~/Documents/study/cmake/009/build$
```
定义了`BUILD_SHARED_LIBS`后生成了`libmylib.so`动态库。
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