[MPI3 Fortran] Results of recent J3 Fortran meeting
longb at cray.com
Thu Oct 21 15:56:57 CDT 2010
N.M. Maclaren wrote:
> On Oct 21 2010, Bill Long wrote:
>> Not sure where compiler options come in here, but...
>> As noted earlier, this is currently an academic issue since the only
>> interoperable character is char. ...
> You have completely missed the point. I am not assuming any type other
> than Fortran default CHARACTER. There are compilers where you have a
> options like -ASCII and -UNICODE, which control which character code
> Fortran uses for its default characters. I can't offhand remember which,
> as I wasn't very interested, but I have seen more than one.
> So a new type code in the Interoperability specification doesn't help,
> because the interface type is default CHARACTER in both cases.
We currently interoperate only with C's char type. On the Fortran side,
the interoperable declaration is character(kind=c_char). Fortran's
default character kind is irrelevant. And sizeof(char) is 1. So there
is no issue here.
> If I can't tell how big a character is from the descriptor, I can't
> write C (i.e. the MPI interface) that will work for both. And that's
> the requirement - having to have different libraries for different
> compiler options is a PAIN.
> Another point here is that I can do this for numeric units, if a compiler
> switches between 4-byte INTEGER and REAL (and 8-byte D.P.) and 8-byte
> INTEGER and REAL (and 16-byte D.P.) But I can't do it for CHARACTER
> with that approach.
> Nick Maclaren
> mpi3-fortran mailing list
> mpi3-fortran at lists.mpi-forum.org
Bill Long longb at cray.com
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