problem building with cmake under cygwin (need clang)

[Csaba Ráduly]

On 16-07-26 06:52 PM, LMH wrote:
> Thanks you for the clarification.
>
> I implemented your steps,
>
> $ ls src/
> CMakeLists.txt  include  README.md  src  test
>
> $ mkdir build
>
> $ cd build/
>
> $ cmake -DCMAKE_CXX_COMPILER=clang  ../src

Stop doing that-----------------------^^^^^^

CMakeLists.txt is in the root of the project. Point cmake to it, like this:

$ cmake  -DCMAKE_CXX_COMPILER=clang++  ..


>
> I get the following output, which is the same error output I was getting
> before. It is different then the errors you are specifying.
>
> -- The C compiler identification is GNU 4.9.3
> -- The CXX compiler identification is unknown
(snip)
>
>
> It looks like it is still using gnu for the compiler and not clang.

There are two different compilers cmake knows about: the C compiler 
(CMAKE_C_COMPILER) and the C++ compiler (CMAKE_CXX_COMPILER). You only 
set the C++ compiler; cmake is using its default for the C compiler.

For quickhull, CMAKE_C_COMPILER probably doesn't matter.

 > It
> looks like it can't identify the c++ compiler at all. I tried this,
>
> cmake -DCMAKE_CXX_COMPILER=clang++ ../src
>

For clang, it makes no difference (clang++ is usually a symlink to clang).

> because I think that CXX is the c++ compiler, but this doesn't make any
> difference. I have attached the cmake error and output logs in case that
> is useful.
>
> It just looks like there is something missing or misconfigured in my
> installation. The which clang and which clang++ commands return the
> expected values. If cmake isn't able to build a test app, then there is
> something wrong at that end I think.


This is what cmake tried:

Run Build Command:"/usr/bin/make.exe" "cmTC_29d2e/fast"
/usr/bin/make -f CMakeFiles/cmTC_29d2e.dir/build.make 
CMakeFiles/cmTC_29d2e.dir/build

make[1]: Entering directory 
'/cygdrive/g/shared_data/SMD/ATomilov_quickhull/build/CMakeFiles/CMakeTmp'

Building CXX object CMakeFiles/cmTC_29d2e.dir/testCXXCompiler.cxx.o

/usr/bin/clang++     -o CMakeFiles/cmTC_29d2e.dir/testCXXCompiler.cxx.o 
-c 
/cygdrive/g/shared_data/SMD/ATomilov_quickhull/build/CMakeFiles/CMakeTmp/testCXXCompiler.cxx

CMakeFiles/cmTC_29d2e.dir/build.make:65: recipe for target 
'CMakeFiles/cmTC_29d2e.dir/testCXXCompiler.cxx.o' failed
make[1]: Leaving directory 
'/cygdrive/g/shared_data/SMD/ATomilov_quickhull/build/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_29d2e/fast' failed
make[1]: *** [CMakeFiles/cmTC_29d2e.dir/testCXXCompiler.cxx.o] Error 127
make: *** [cmTC_29d2e/fast] Error 2


Try to run those commands manually:

$ cd 
'/cygdrive/g/shared_data/SMD/ATomilov_quickhull/build/CMakeFiles/CMakeTmp'

$ /usr/bin/clang++     -o 
CMakeFiles/cmTC_29d2e.dir/testCXXCompiler.cxx.o -c 
/cygdrive/g/shared_data/SMD/ATomilov_quickhull/build/CMakeFiles/CMakeTmp/testCXXCompiler.cxx

What is the output?


Csaba
-- 
Life is complex, with real and imaginary parts.
The Tao of math: The numbers you can count are not the real numbers.

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