CMAKE 未定义 CYGWIN 变量

Question

我在 Windows 7 64 位下的 cygwin 控制台上使用 cmake。但是，cmake 变量 CYGWIN ( https://cmake.org/cmake/help/v3.3/variable/CYGWIN.html ) 未定义。我错过了什么吗？

例如，这是我的 CMakeLists.txt:

message("CYGWIN: ${CYGWIN}")
message("CMAKE SYSTEM: ${CMAKE_SYSTEM_NAME}")
project ( foo CXX)

我启动 cygwin 控制台并执行以下操作:

cmake path/to/my/CMakeLists.txt

选定的输出:

>    CYGWIN: 
>    CMAKE SYSTEM:
> -- The CXX compiler identification is GNU 4.9.2
> 
>    ( a warning about the WIN32 variable not being defined by cmake anymore)
> 
> -- Check for working CXX compiler: /usr/bin/x86_64-w64-mingw32-g++.exe
> -- Check for working CXX compiler: /usr/bin/x86_64-w64-mingw32-g++.exe -- works
> -- Detecting CXX compiler ABI info
> -- Detecting CXX compiler ABI info - done
> -- Detecting CXX compile features
> -- Detecting CXX compile features - done
> -- Check for working C compiler: /usr/bin/x86_64-w64-mingw32-gcc.exe
> -- Check for working C compiler: /usr/bin/x86_64-w64-mingw32-gcc.exe -- works
> -- Configuring done
> -- Generating done
> -- Build files have been written to: /foo/directory

配置:

• 命名 CYGWIN_NT-6.1
• cmake 版本 3.3.2(CMake 套件由 Kitware (kitware.com/cmake) 维护和支持。

Answer 1

CYGWIN cmake 变量由 project() 命令定义。将其移到 message 命令之前可以解决问题。

CMakeLists.txt:

project(foo CXX)
message("CYGWIN: ${CYGWIN}")
message("CMAKE SYSTEM: ${CMAKE_SYSTEM_NAME}")

相关输出:

> -- The CXX compiler identification is GNU 4.9.2
>    (a lot of talking)
>    CYGWIN: 1
>    CMAKE SYSTEM: CYGWIN