To: J3                                                     J3/19-238r1
From: Daniel Chen & Bill Long
Subject: C_F_POINTER modification for feature UK-01
Date: 2019-October-15

Reference: WG5/N2167, 18-007r1, 19-194r1

Introduction
------------

UK feature for F202X in WG5/N2167: UK-01

A pointer assignment allows an array pointer to have lower bounds
other than 1. Intrinsic subroutine C_F_POINTER does not. This feature
proposes to add the capability to specify lower bounds for the FPTR
array in C_F_POINTER.

Requirement:
------------

Allow specification of lower bounds for the FPTR argument in a call to
C_F_POINTER.


Specification and Syntax:
-------------------------

Add an optional argument, LOWER, to the end of the argument list for
C_F_POINTER. The LOWER argument is an integer array of rank one and
the same size as the SHAPE argument. The values of the elements of
LOWER are the lower bounds for the corresponding dimensions of the
pointer FPTR. If LOWER is not present, the lower bounds for each
dimension of FPTR are 1.


Edits to 18-007r1
----------------

[xiii] Introduction
Add "The subroutine C_F_POINTER in the intrinsic module ISO_C_BINDING
has an extra optional dummy argument, LOWER that specifies the lower
bounds of FPTR."

[470:13] Subclause 18.2.3.3 C_F_POINTER (CPTR, FPTR [, SHAPE])
replace "[, SHAPE]" by "[, SHAPE, LOWER]"

The line now reads:
18.2.3.3 C_F_POINTER (CPTR, FPTR [, SHAPE, LOWER])


[470:24-25] Subclause 18.2.3.3 C_F_POINTER (CPTR, FPTR [, SHAPE])
replace
" and each lower bound is equal to 1." by
"; the lower bounds are specified by LOWER if it is present, and
otherwise are equal to 1."

The line now reads:
"If FPTR is an array, its shape is specified by SHAPE; the lower
bounds are specified by LOWER if it is present, and otherwise
are equal to 1."


[471:21-22] Subclause 18.2.3.3 C_F_POINTER (CPTR, FPTR [, SHAPE])
In Case (iii), replace " and each lower bound is 1" by
". The lower bounds are specified by LOWER if it is
present;  otherwise each lower bound is equal to 1."

The line now reads:
"If FPTR is an array, its shape is specified by SHAPE. The lower
bounds are specified by LOWER if it is present; otherwise each
lower bound is equal to 1."


[471:26+] Subclause 18.2.3.3 C_F_POINTER (CPTR, FPTR [, SHAPE])
After the definition of SHAPE, add:
"LOWER (optional) shall be a rank-one integer array. It is an
        INTENT (IN) argument. It shall not be present if SHAPE
        is not present. If LOWER is present, its size
        shall be equal to the rank of FPTR."


[471:37-45] Examples.
replace Case (ii) by:
"
  Type t
    Real, Allocatable :: v(:,:)
  End Type
  Type(t), Target :: x(0:2)
  Type(t), Pointer :: y (:)
  Type(C_ptr) :: xloc
  xloc = C_Loc (x)
  ...
  Call C_F_Pointer (xloc, y, [3], [0])
"