[CMake] Clang + MinGW Linking Issue

[Justin Holewinski]

On Thu, May 24, 2012 at 10:08 AM, Brad King <brad.king at kitware.com> wrote:

> 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.
>

Oops, missed that issue.  Sorry about that!


>
> >  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?
>

This works for the MinGW build.  I really can't say if this fixes the
library naming issue for the MS-style Clang.  Clang does not have a
VC-compatible driver (that I know of) so does not accept VC-style arguments
like "/O2", which causes CMake to fail early on in the configure process
when using the NMake generator.  Clang with MinGW is the only really
supported configuration at this point.


>
> Thanks,
> -Brad
>



-- 

Thanks,

Justin Holewinski
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