[MPI3 Fortran] Start discussing new Fortran binding

[Craig Rasmussen]

On Feb 19, 2008, at 8:38 AM, Lionel, Steve wrote:

>>
>> 2. Is there a way to use a preprocessor to replace something like  
>> this
>>
>>        integer(MPI_HANDLE_TYPE), value, intent(in) :: datatype
>>
>> with either C_INT or C_PTR, depending on what the implementation
>> requires?
>
> The proper (IMO) way to do this in Fortran is as follows:
>
> type, BIND(C) :: MPI_HANDLE_TYPE
>   private
>   type(C_PTR) :: handle
>   end type MPI_HANDLE_TYPE
>
> This allows the user to declare things of type(MPI_HANDLE_TYPE) but
> makes the contents inaccessible other than passing, storing or  
> fetching.
> The BIND(C) tells the Fortran compiler that this is an interoperable
> type and it is not allowed to pad it or rearrange the contents.
>>

Jeff and I tried to make this work out in our paper but thought there  
might be problems interfacing with exiting MPI implementations.   
However, I agree this would be a better approach if it can be made to  
work with MPI implementations that work with both integers and  
pointers to structs.  I'll think some more about how to use your  
approach, perhaps you could add you brain power to it as well.

I think this should be the main topic for conversation in our telecon  
this week.  Agree?

Cheers,
Craig