llvm dev - Jan 2018 - CMake warning when compiling Clang/LLVM

Am 2018-01-26 21:36, schrieb Tom Stellard via llvm-dev:
> On 01/26/2018 12:32 PM, Simone Atzeni via llvm-dev wrote:
>> Hi,
>> 
>> when I run cmake I get the following warning:
>> 
>>
---------------------------------------------------------------------------------------
>> CMake Warning at cmake/modules/HandleLLVMStdlib.cmake:24 (message):
>>   Can't specify libc++ with '-stdlib='
>> Call Stack (most recent call first):
>>   cmake/config-ix.cmake:15 (include)
>>   CMakeLists.txt:580 (include)
>>
---------------------------------------------------------------------------------------
>> 
>> I am using GCC 4.8.5 to build on a x86_64 machine with RedHat OS.
>> 
>> Any idea why?
> 
> What arguments are you passing to CMake and which version of LLVM are 
> you
> trying to build?
That's probably -DLLVM_ENABLE_LIBCXX=ON and the warning tells you the 
reason: -stdlib= is only supported if compiling with Clang, you can't 
specify it with GCC.

Cheers,
Jonas

Thanks, that's the reason.

So to clarify, I should use -DLLVM_ENABLE_LIBCXX=ON only if I am building
clang with clang?
I got confused, I thought it was for building libc++, but having that under
projects seems to be enough.

Thanks.
Simone
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Am 2018-01-26 21:55, schrieb Simone Atzeni:
> Thanks, that's the reason.
> 
> So to clarify, I should use -DLLVM_ENABLE_LIBCXX=ON only if I am
> building clang with clang?
> I got confused, I thought it was for building libc++, but having that
> under projects seems to be enough.
If libc++ is under projects/ it will get built. What LLVM_ENABLE_LIBCXX 
does is to enable _linking_ all LLVM libraries and binaries to libc++ as 
the C++ STL and that's only supported with Clang. You can specify the 
option when building with GCC, it just won't work and issue the warning 
you are seeing.

Regards,
Jonas