.
├── client
│ └── main.cpp
├── CMakeLists.txt
├── main.cpp
└── server
└── main.cpp
2 directories, 4 files
这里一共生成了三个可执行文件，CMake如下：
project(Demo)
add_executable(demo main.cpp)
add_executable(server ./client/main.cpp)
add_executable(client ./client/main.cpp)
