llvm dev - Jan 2017 - ABI breaking check magic breaks check_include_cxx_file() in CMake

Hi,

I've just discovered that with LLVM 4.0, LightSpark suddenly fails to
find all LLVM include files. I've looked into it, and it seems that
CMake is doing the very smart thing of attempting to link the test
applications using the tested includes, and this fails with:

/usr/bin/c++        CMakeFiles/cmTC_cd252.dir/CheckIncludeFile.cxx.o  -o
cmTC_cd252 -rdynamic
CMakeFiles/cmTC_cd252.dir/CheckIncludeFile.cxx.o:(.data+0x0): undefined
reference to `llvm::DisableABIBreakingChecks'
collect2: error: ld returned 1 exit status

I've reported this upstream at [1]. However, do you have any idea how
we could work around the problem on our end before CMake is fixed
and all users upgrade it?

[1]:https://gitlab.kitware.com/cmake/cmake/issues/16606

-- 
Best regards,
Michał Górny
<http://dev.gentoo.org/~mgorny/>
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Hi,
> On Jan 28, 2017, at 1:26 AM, Michał Górny via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> I've just discovered that with LLVM 4.0, LightSpark suddenly fails to
> find all LLVM include files. I've looked into it, and it seems that
> CMake is doing the very smart thing of attempting to link the test
> applications using the tested includes, and this fails with:
> 
> /usr/bin/c++        CMakeFiles/cmTC_cd252.dir/CheckIncludeFile.cxx.o  -o
cmTC_cd252 -rdynamic
> CMakeFiles/cmTC_cd252.dir/CheckIncludeFile.cxx.o:(.data+0x0): undefined
reference to `llvm::DisableABIBreakingChecks'
> collect2: error: ld returned 1 exit status
> 
> I've reported this upstream at [1]. However, do you have any idea how
> we could work around the problem on our end before CMake is fixed
> and all users upgrade it?
You can build LLVM with -DLLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING=OFF

— 
Mehdi

> 
> [1]:https://gitlab.kitware.com/cmake/cmake/issues/16606
> 
> -- 
> Best regards,
> Michał Górny
> <http://dev.gentoo.org/~mgorny/>
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