[MPI3 Fortran] Results of recent J3 Fortran meeting

[N.M. Maclaren]

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.

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.


Regards,
Nick Maclaren