[CMake] Fortan and C++

[Michael Wild]

Reported the issue with FortranCInterface.cmake here: http://www.vtk.org/Bug/view.php?id=9446

Michael

On 22. Aug, 2009, at 14:03, Michael Wild wrote:

> Hi Dominik
>
> Concerning the flags: you should add the -no-multibyte-chars to the  
> CMAKE_CXX_FLAGS variable. This will get prepended to all  
> CMAKE_CXX_FLAGS_{RELEASE,DEBUG,...} flags, since you don't want this  
> flag to be used for the Release configuration exclusively, but for  
> all configurations.
>
> Linking against ifcore using the C++ compiler only works if it is on  
> the search path (probably by sourcing ifortvars.sh), otherwise  
> you'll have to specify it's full path. I think, Intel recommends  
> using the the Fortran compiler for linking instead, and passing it  
> the -cxxlib and -nofor_main flags (those are the correct names now,  
> I looked them up ;-)).
>
> On Mac platforms there is another problem: By default the g++  
> compiler generates 32-bit code, while the Intel Fortran compiler  
> generates 64-bit code (very annoying).
>
> If you try to use FortranCInterface.cmake, be aware that it is quite  
> buggy, as it doesn't pass the CMAKE_*_FLAGS to the try_compile  
> calls. Further it doesn't ensure that the C language is enabled,  
> altough it is calling try_compile on C code! I'll file a bug report  
> with an attached patch for that.
>
> All the best
>
> Michael
>
> On 22. Aug, 2009, at 13:35, Dominik Szczerba wrote:
>
>> Here the report of my tests:
>>
>> Just ignorant approach (don't google):
>>
>> It works out of the box on linux with intel compilers 10.x. Just  
>> add Fortran to the languages in the project signature and add  
>> STUFF.F90 to the source files. You need to link to ifcore library  
>> though.
>>
>> It does not work out of the box with the compilers 11.x. Here the  
>> ignorant approach failed. The errors were like:
>>
>> -- Check for working CXX compiler: /usr/local/bin/icpc-11.0.083
>> -- Check for working CXX compiler: /usr/local/bin/icpc-11.0.083 --  
>> broken
>> CMake Error at /usr/local/share/cmake-2.6/Modules/ 
>> CMakeTestCXXCompiler.cmake:25 (MESSAGE):
>> The C++ compiler "/usr/local/bin/icpc-11.0.083" is not able to  
>> compile a
>> simple test program.
>>
>> It fails with the following output:
>>
>>  Change Dir: /home/domel/build/solve/CMakeFiles/CMakeTmp
>>
>> Checking by foot what the compilers at all say during compilations  
>> I found:
>>
>> > icpc-11.0.083 -c test.cxx
>> Catastrophic error: could not set locale "" to allow processing of  
>> multibyte characters
>>
>> Googling reveals a bug in the compiler to be circumvented with  
>> adding '-no-multibyte-chars' to the compiler switches. However,  
>> adding this to my CMAKE_XXX_FLAGS_RELEASE (my CMAKE_BUILD_TYPE is  
>> RELEASE) does not help. I must now either specify CMAKE_XXX_FLAGS  
>> explicitly on the commandline or in the cache. Probably because  
>> cmake uses default flags (CMAKE_XXX_FLAGS) for compiler checks,  
>> even if CMAKE_BUILD_TYPE is explicitly set release/debug (as well  
>> as corresponding release/debug flags).
>>
>> Maybe cmake should use compiler flags as defined by  
>> CMAKE_BUILD_TYPE to check for compilers?
>>
>> - Dominik
>>
>>
>>
>> Dominik Szczerba wrote:
>>> Michael,
>>> Many thanks for the feedback.
>>> What I am doing with a GNU makefile so far is compile just one  
>>> file with the fortran compiler use C++ linker to link all object  
>>> files as usual.
>>> A comprehensive solution I would expect in cmake would be 1)  
>>> nothing (.f90 file is understood) or something along the lines of  
>>> setting the file properties (sort of 'to be compiler with' flag)...
>>> - Dominik
>>> Michael Wild wrote:
>>>>
>>>>
>>>> On 21.08.2009, at 17:57, Dominik Szczerba <dominik at itis.ethz.ch>  
>>>> wrote:
>>>>
>>>>> I want to compile one file with fortran compiler (intel) and  
>>>>> link  with the rest of my project. Will the latest cmake allow  
>>>>> to fully  cmakify such scenario?
>>>> Hi Dominik
>>>>
>>>> If I remember correctly, you'll have to set the LINK_LANGUAGE  
>>>> property  of your target to Fortran and then ensure that the  
>>>> Fortran linker also  links against the C++ standard library. For  
>>>> Intel this would be -stdc+ + (or some such). If you are creating  
>>>> an executable, depending on  where your main-function is defined,  
>>>> you might also need to tell the  linker to not add a Fortran main- 
>>>> function, the flag is called - nofor_main if I remember  
>>>> correctly. Otherwise the ifort man-page will  tell you :)
>>>>
>>>>
>>>> HTH
>>>>
>>>> Michael
>>
>>
>> -- 
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>