[CMake] Clang + MinGW Linking Issue

[Keith Gardner]

I have built clang (llvm) on windows with Visual Studio 2010 and used the built binaries as the compiler inside of a Visual Studio project.  This was with clang 3.0 and llvm 2.9.1.

From: cmake-bounces at cmake.org [mailto:cmake-bounces at cmake.org] On Behalf Of Justin Holewinski
Sent: Thursday, May 24, 2012 1:49 PM
To: Brad King
Cc: cmake at cmake.org
Subject: Re: [CMake] Clang + MinGW Linking Issue

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