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Re: problem building with cmake under cygwin (need clang)


On Tue, Jul 26, 2016 at 8:16 AM, Marco Atzeri  wrote:
>
> On 26/07/2016 02:45, LMH wrote:
>>
>> Hello,
>>
>> I am trying to compute the convex hull of a high dimensional space (46D
>> x 2000 rows). The qhull app available in cygwin/math is based on
>> relatively old code and runs out of memory.
>>
>> I found another version the is supposed to be able to do higher
>> dimensions.
>>
>> https://bitbucket.org/tomilov/quickhull/src
>>
>> This version is set up to build with cmake, so I installed cmake in
>> cygwin and ran it as,
>>
>> cmake ./src
>>
>> Note, I had to copy CMakeLists.txt into the src directory to get this to
>> work. If I don't do that, I get the error,
>>
>> CMake Error: The source directory
>>
>> "/cygdrive/g/shared_data/SMD/ATomilov_quickhull/tomilov-quickhull-7faf277d6cc2_cmake/src"
>> does not appear to contain CMakeLists.txt.
>>
>> When I have copied the CMakeLists.txt file into ./src, cmake runs but I
>> get the error,
>>
>> CMake Error at CMakeLists.txt:11 (message):
>>   only clang supported currently
>>
>> this comes from the conditional,
>>
>> if(NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
>>     message(FATAL_ERROR "only clang supported currently")
>> endif()
>>
>> in CMakeLists.txt.
>>
>> I have installed clang from cygwin, but I still get the same error. I
>> added the following line to CMakeLists.txt,
>>
>> message(STATUS "${CMAKE_CXX_COMPILER_ID}")
>>
>> and I get "GNU" as the value for CMAKE_CXX_COMPILER_ID, at least that is
>> the value if I got the syntax correct for the message statement.
>>
>> It looks like I need to point CMAKE_CXX_COMPILER_ID to clang, but I am
>> not sure how to do that. I don't know if the problem is with the
>> CMakeLists.txt file, the way I am calling cmake, or with my local cygwin
>> configuration.
>>
>> Suggestions would be appreciated.
>>
>> LMH
>>
>>
>
>
> the build system of quickhull has some serious problem.
>
> set
>
> CMAKE_CXX_COMPILER               /usr/bin/clang-3.8.exe
> CMAKE_C_COMPILER                 /usr/bin/clang-3.8.exe
>
> after you will hit
>
>  CMake Error at CMakeLists.txt:22 (message):
>    Compiler does not support C++1z standard
>
> if you look on CMakeLists.txt you will find is expecting a flag
> as "-std=gnu++1z"  that looks a bit strange for a not gnu compiler

Clang implements many of GCC's extensions. -std=gnu++1something means
"C++ 1something with GNU extensions". Clang understands that just
fine.

Csaba
-- 
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The Tao of math: The numbers you can count are not the real numbers.
Life is complex, with real and imaginary parts.
"Ok, it boots. Which means it must be bug-free and perfect. " -- Linus Torvalds
"People disagree with me. I just ignore them." -- Linus Torvalds

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