[CMake] Fortan and C++

Michael Wild themiwi at gmail.com
Sat Aug 22 09:45:47 EDT 2009 

As I said, FortranCInterface.cmake is buggy as it doesn't pass the  
CMAKE_Fortran_FLAGS and CMAKE_EXE_LINKER_FLAGS variables to the  
TRY_COMPILE project. If you have to set these in order to compile/link  
a mixed-language program, it fails. Come to think of it, in your case  
the ifcore library will also be missing, so probably something like a  
CMAKE_REQUIRED_LIBRARIES variable will also be necessary.

Michael

On 22. Aug, 2009, at 15:40, Dominik Szczerba wrote:

> I naively tried:
>
> INCLUDE(FortranCInterface)
> CREATE_FORTRAN_C_INTERFACE(myf cross myfconfig.h)
>
> to get:
>
> -- checking Fortran function linkage: sub_
> -- checking Fortran function linkage: _sub_
> -- checking Fortran function linkage: __sub_
> -- checking Fortran function linkage: SUB_
> -- checking Fortran function linkage: _SUB_
> -- checking Fortran function linkage: __SUB_
> -- checking Fortran function linkage: sub
> -- checking Fortran function linkage: _sub
> -- checking Fortran function linkage: __sub
> -- checking Fortran function linkage: SUB
> -- checking Fortran function linkage: _SUB
> -- checking Fortran function linkage: __SUB
> CMake Error at /usr/local/share/cmake-2.6/Modules/ 
> FortranCInterface.cmake:169 (message):
>  Could not find fortran c name mangling.
> Call Stack (most recent call first):
>  CMakeLists.txt:34 (create_fortran_c_interface)
>
> I have C CXX and Fortran enabled in the 'project' call. Using icpc/ 
> ifort 11.x
>
> - Dominik
>
> Dominik Szczerba wrote:
>> Hi Michael,
>> 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.
>> Thanks for the clarifications.
>>> 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 ;-)).
>> I see, will maybe try some day. However, I have no problem linking  
>> for the moment.
>>> 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.
>>>
>> This is new to me. Sounds like automatic handling of calling  
>> decorations. Would be great! Are there any examples how to use it?  
>> Do I still need it when I know the mangling scheme myself? Can I  
>> set the pre/suffixes myself in some elegant manner? Currently I am  
>> just hacking on my own, so indications how to position myself for  
>> the future are very welcome.
>> Thanks,
>> Dominik
>>> 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
>>>> -- 
>>>> d o m i n i k   s z c z e r b a ,   p h d . . . . . . . . . . .
>>>> c o m p u t a t i o n a l   l i f e   s c i e n c e   g r o u p
>>>> . . . . . . . i t ' i s   r e s e a r c h   f o u n d a t i o n
>>>> . . . . . . . . . . . . . . . . . . . . http://www.itis.ethz.ch
>>>>
>
>
> -- 
> d o m i n i k   s z c z e r b a ,   p h d . . . . . . . . . . .
> c o m p u t a t i o n a l   l i f e   s c i e n c e   g r o u p
> . . . . . . . i t ' i s   r e s e a r c h   f o u n d a t i o n
> . . . . . . . . . . . . . . . . . . . . http://www.itis.ethz.ch
>

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