上回的CMakeLists.txt里面有一句，if (WIN32)......endif(WIN32)；

根据资料，这是判断操作系统是否是Windows；

下面单独看一下；

一个CMakeLists.txt文件如下；

if(WIN32)
    # 如果是 Windows
    message("当前操作系统为 Windows")
elseif(UNIX AND NOT APPLE)
    # 如果是 Linux
    message("当前操作系统为 Linux")
else()
    message(FATAL_ERROR "不支持的操作系统类型")
endif()

然后运行看一下，如下图；

 

它有一些输出；

CMake Warning (dev) in CMakeLists.txt:
No project() command is present. The top-level CMakeLists.txt file must
contain a literal, direct call to the project() command. Add a line of
code such as

project(ProjectName)

near the top of the file, but after cmake_minimum_required().

CMake is pretending there is a "project(Proj