To: J3                                                     J3/18-210r1
From: Bill Long & Daniel Chen & Malcolm Cohen
Subject: Ballot Comment GB056
Date: 2018-June-13


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,
Change "simply contiguous dummy argument"
to "dummy argument whose designator would be simply contiguous",
making the paragraph read
  "When an interoperable Fortran procedure with a dummy argument whose
   designator would be simply contiguous is invoked from C and the actual
   argument is the address of a C descriptor for a discontiguous object,
   the Fortran processor shall handle the difference in contiguity."
ALTERNATIVE:
  "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,
Change "simply contiguous dummy argument"
to "dummy argument whose designator would be simply contiguous",
making the paragraph read
  "When an interoperable C procedure whose Fortran interface has a dummy
   argument whose designator would be simply contiguous 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."
ALTERNATIVE:
  "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."
{The non-alternative is more concise but more grammatically intense,
 while the alternative is more verbose but also more comprehensible?}

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===