[CMake] Fortan and C++

[Dominik Szczerba]

You are well informed. So this standard is implemented in icc/ifort 11.x 
but not (yet) GNU? This renders the FortranCInterface.cmake rather 
obsolete, does it not?

Yes, it looks rather excessive, but at least clean.

Thanks,
Dominik

Michael Wild wrote:
> On 22. Aug, 2009, at 15:29, Dominik Szczerba wrote:
> [...]
>>> 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
> [...]
> 
> Exactly. It first tries to figure out the name-mangling scheme used by  
> your Fortran compiler. I think it tries to prepend/append _ up to two  
> times and also tries lower/upper case variations. For names containing  
> a _, it also detects whether the compiler appends an additional _  
> charachter. Then it creates a header file containing preprocessor  
> defines, mapping the "names as written" to the mangled names.
> 
> This would be all great and nice, if it wasn't buggy... *sigh*
> 
> With reference to the future: the Intel compiler supports the  
> iso_c_binding intrinsic module defined for Fortran 2003, allowing one  
> to do something like this:
> 
> -- >8 --
> 
> ! Fortran native function
> real function super_duper(a)
>    implicit none
>    real, intent(in) :: a
>    super_duper = a**2
> end function super_duper
> 
> ! C-wrapper function
> real(c_float) function c_super_duper(a) bind(c)
>    use, intrinsic :: iso_c_binding
>    implicit none
>    real (c_float), intent(in), value :: a
>    real, external :: super_duper
>    c_super_duper = super_duper(a)
> end function c_super_duper
> 
> -- <8 --
> 
> And then in your C++ file you write:
> 
> -- >8 --
> 
> #include <iostream>
> 
> extern "C" {
>    float c_super_duper(float);
> }
> 
> int main() {
>    std::cout << "super_duper(10) = " << c_super_duper(10.0) << "\n";
>    return 0;
> }
> 
> -- <8 --
> 
> It is very verbose and also a bit confusing, but it takes care of all  
> the name-mangling issues and also does the type-handling correctly. As  
> you can see, the argument is passed by value by adding the VALUE  
> attribute in the wrapper function.
> 
> Michael
> 


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