[CMake] Clang + MinGW Linking Issue

[Brad King]

On 05/24/2012 12:22 PM, Justin Holewinski wrote:
> I narrowed the problem down to Clang not having Platform/Windows-Clang-{C,CXX}.cmake files.

There is an issue tracker entry for this:

  http://www.cmake.org/Bug/view.php?id=13035

but it is in the backlog waiting for more feedback and a volunteer.
The main problem is distinguishing the GNU-compatible and MS-compatible
builds of Clang.

>  If I add the following two files then everything starts to work as expected:
> 
> Platform/Windows-Clang-C.cmake:
> 
> if(MINGW)
>   include(Platform/Windows-GNU)
>   __windows_compiler_gnu(C)
> else()
>   # Chain to generic Windows configuration
>   include(Platform/Windows)
> endif()
> 
> Platform/Windows-Clang-CXX.cmake:
> 
> if(MINGW)
>   include(Platform/Windows-GNU)
>   __windows_compiler_gnu(C)
> else()
>   # Chain to generic Windows configuration
>   include(Platform/Windows)
> endif()
> 
> This way, using Clang with MinGW will force GNU-style platform
> options instead of VS-style Windows options.
> Is this more or less the "right way" to fix this in CMake?

Interesting approach.  That may be better than separating the
compiler id as mentioned in the above-linked issue.  The "MINGW"
value is set based on CMAKE_C_PLATFORM_ID which is computed in
the same way and at the same time as CMAKE_C_COMPILER_ID.  Try:

 $ cat Platform/Windows-Clang-C.cmake
 if("${CMAKE_C_PLATFORM_ID}" MATCHES "MinGW")
   include(Platform/Windows-GNU-C)
 else()
   include(Platform/Windows-cl)
 endif()

 $ cat Platform/Windows-Clang-CXX.cmake
 if("${CMAKE_CXX_PLATFORM_ID}" MATCHES "MinGW")
   include(Platform/Windows-GNU-CXX)
 else()
   include(Platform/Windows-cl)
 endif()

Do you have both the MS-style and GNU-style Clang available
to test?

Thanks,
-Brad