To:       J3                                                      07-297r2
From:     Jim Xia
Subject:  Interpretation: Evaluation of bound-expr in data pointer
          assignment
Date: 2007 November 14

NUMBER:   F03/0102
TITLE:    Evaluation of bound-expr in data pointer assignment
KEYWORDS: pointer, pointer assignment, bounds, expression
DEFECT TYPE: Error
STATUS:   Erratum

DISCUSSION

Currently there are no rules in 7.4.2.1 to prohibit changing of a
pointer's association status during evaluation of bound expressions
in a data pointer assignment (pointer with either bounds-spec or
bounds-remapping specified).  This may lead to ambiguous code with
regard to the evaluation orders between the bound expression and
the data pointer assignment itself.  Consider the following code,


    integer,  target  :: tar2(100, 100)
    integer,  target  :: tar1(100)
    integer,  pointer :: ptr(:,:)

    ptr(-2:, f1(ptr, tar1, 1, 1):) => tar2

    print*, lbound(ptr)
    print*, ubound(ptr)
    print*, size(ptr)

    contains

    function f1(ptr, arr, i, j)
        integer  :: i, j, f1
        integer, pointer :: ptr(:, :)
        integer, target  :: arr(:)

        ptr (i:j, i:j) => arr
        f1 = -1
    end function

    end


In 7.4.1.3 for interpretation of intrinsic assignments, there are rules
explicitly requesting evaluation of all expressions in variable occurred
before the variable is defined [139:14-19].  It appears that data pointer
assignment should also follow similar rules.

Note the similar problem also exists for evaluating the <data-target> if
it references a function that returns a data pointer.


QUESTION:

    (a) Is this program intended to be standard conforming?

    (b) If it is standard conforming, then what would it print?


ANSWER:

    (a) No, this program is not intended to be standard conforming.

Edits are provided to clarify this.

EDITS:

[04-007:128:6] After "undefinition" insert ", or changes the pointer
association status or allocation status,"

SUBMITTED BY: Jim Xia

HISTORY: 07-297r1 m182 Submitted
         07-297r2 m182