To: J3                                                     J3/18-210r2
From: Bill Long & Daniel Chen & Malcolm Cohen
Subject: Ballot Comment GB056
Date: 2018-June-14


Ballot Comment
--------------

In their DIS Ballot for draft N2146 of Fortran 2018, the GB comment
056 reads:

"The term "simply contiguous dummy variable" is undefined. Moreover as
described in NOTE 18.22 it is inconsistent with the current standard."


with the suggested edits:

In paragraph 5 change "simply contiguous dummy argument" to "dummy
argument which has the CONTIGUOUS attribute, or is an assumed-length
CHARACTER array and not a pointer, assumed-shape, or assumed-rank,".

Make the same change in paragraph 6.

Delete paragraph 7.

Delete NOTE 18.22

Add a new NOTE 18.22:

"If an interoperable C procedure whose Fortran interface has a dummy
argument which has the CONTIGUOUS attribute, or is an assumed-length
CHARACTER array and not a pointer, assumed-shape, or assumed-rank, is
invoked from C, the invoking routine is responsible for the contents
of the C descriptor which therefore might not describe a contiguous
data object."


Discussion
----------

Subgroup in principle agrees with the comment. We also modified the
edit as:

1. "simply contiguous dummy argument" could be replaced by
   "dummy argument whose designator would be simply contiguous".
   However, this obscures the fact that it is only a couple of cases
   that are affected, viz
    "CONTIGUOUS attribute or assumed-length CHARACTER array that is
     explicit-shape or assumed-size".
  OTOH that is rather a mouthful in a long sentence.

2. An interoperable assumed-length CHARACTER array cannot be
allocatable or pointer; An interoperable CHARACTER array that is
allocatable or pointer must have deferred length, so we removed the
"a pointer, ".



Edit to N2146
-------------

Page 490, 18.3.7 Interoperability of procedures and procedure
interfaces,

para5,
  After "When an interoperable Fortran procedure"
  change "with a simply contiguous dummy argument" to "that",
  After "is invoked from C"
  insert "has a dummy argument with the CONTIGUOUS attribute or that is an
          assumed-length CHARACTER explicit-shape or assumed-size array,"
making the paragraph read
  "When an interoperable Fortran procedure that is invoked from C has a
   dummy argument with the CONTIGUOUS attribute or that is an assumed-
   length CHARACTER explicit-shape or assumed-size array, and the actual
   argument is the address of a C descriptor for a discontiguous object,
   the Fortran processor shall handle the difference in contiguity."
{The non-alternative is more concise but more grammatically intense,
 while the alternative is more verbose but also more comprehensible?}

Paragraph 6,
  After "When an interoperable C procedure whose Fortran interface has a"
  change "simply contiguous dummy argument"
  to "dummy argument with the CONTIGUOUS attribute or that is an assumed-
      length CHARACTER explicit-shape or assumed-size array"
making the paragraph read:
  "When an interoperable C procedure whose Fortran interface has a dummy
   argument with the CONTIGUOUS attribute or that is an assumed-length
   CHARACTER explicit-shape or assumed-size array is invoked from Fortran
   and the effective argument is discontiguous, the Fortran processor
   shall ensure that the C procedure receives a descriptor for a
   contiguous object."

Delete paragraph 7 "When... handle the discontiguous argument.".

Delete NOTE 18.22 "The requirements on the Fortran... or a pointer.".

Add a new NOTE 18.22:

"If an interoperable C procedure whose Fortran interface has a dummy
 argument which has the CONTIGUOUS attribute, or is an assumed-length
 CHARACTER explicit-shape or assumed-size array, is invoked from C,
 because the invoking routine is responsible for the contents of the C
 descriptor, it therefore might not describe a contiguous data object."

===END===