(j3.2006) Should Fortran processor handle the contiguity of an assumed-length assumed-size/explicit-shape dummy argument of a bind(c) procedure?

[Daniel C Chen]

Hi Malcolm,

Thanks for clarifying it.

Daniel

XL Fortran Development - IBM Toronto Software Lab
Phone: 905-413-3056
Tie: 969-3056
Email: cdchen at ca.ibm.com
http://www.ibm.com/software/awdtools/fortran/xlfortran



From:	"Malcolm Cohen" <malcolm at nag-j.co.jp>
To:	"fortran standards email list for J3"
            <j3 at mailman.j3-fortran.org>,
Date:	10/08/2014 21:41
Subject:	Re: (j3.2006) Should Fortran processor handle the contiguity of
            an	assumed-length assumed-size/explicit-shape dummy argument
            of	a bind(c) procedure?
Sent by:	j3-bounces at mailman.j3-fortran.org



Hi Daniel,

This does seem to be unspecified, probably because we just expected it to
work that way, the same as it does without BIND(C) since that?s a Fortran
77 style dummy (the number of F77 compilers prepared to accept
discontiguous array slice actual arguments for an assumed-size dummy can be
numbered on the fingers of one foot).

I think this is a defect.  In the paragraph you quote, after ?with the
CONTIGUOUS attribute?, it should probably say something not entirely unlike
?, an explicit-shape or assumed-size array with assumed character length,
or an assumed-size array with assumed type?.  Probably more words need to
go in here.  However, the quoted paragraph needs a complete rewrite as it
is nonsense anyway (see UTI005) so we don?t need to wordsmith this fix now.

i.e. IMO yes the Fortran processor should handle this ?properly?, the same
as we require for CONTIGUOUS assumed-shape, and we need to state this.

Cheers,


From: Daniel C Chen
Date: ?? 26?10?9? 0:30
To: j3 at mailman.j3-fortran.org
Subject: (j3.2006) Should Fortran processor handle the contiguity of an
assumed-length assumed-size/explicit-shape dummy argument of a bind(c)
procedure?



Hello,

Please consider the following Fortran procedure,

  subroutine sub(arg1, arg2) bind(c)
    character(*) :: arg1(*)
    character(*) :: arg2(2,3)
    .....
    .....
  end subroutine

TS29113 specifies that both arg1 and arg2 correspond to a CFI descriptor as
they are assumed-length. However, I couldn't find words in the standard or
TS that explicitly specifies if Fortran processor is supposed to handle the
contiguity inside "sub" for arg1 and arg2 in the case that the caller is a
C function that passes non-contiguous CFI descriptor actual arguments.

The closest I found is:

"In an invocation of an interoperable procedure whose Fortran interface has
an assumed-shape or assumed-rank
dummy argument with the CONTIGUOUS attribute, the associated effective
argument may be an array that is
not contiguous or the address of a C descriptor for such an array. If the
procedure is invoked from Fortran or the
procedure is a Fortran procedure, the Fortran processor will handle the
difference in contiguity. If the procedure
is invoked from C and the procedure is a C procedure, the C code within the
procedure shall be prepared to
handle the situation of receiving a discontiguous argument."

TIA,

Daniel

XL Fortran Development - IBM Toronto Software Lab
Phone: 905-413-3056
Tie: 969-3056
Email: cdchen at ca.ibm.com
http://www.ibm.com/software/awdtools/fortran/xlfortran
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................................Malcolm Cohen, Nihon NAG, Tokyo.
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