J3/14-223r1
To:      J3
From:    Nick Maclaren & Malcolm Cohen
Subject: TARGET and coindexed arguments
Date: 2014 October 14

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NUMBER: F08/0117
TITLE: TARGET and coindexed arguments
KEYWORD: TARGET, coindexing
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Is the following program conforming and required to print 10, 10, 10
and 123, 123, 123?

PROGRAM Main
    INTEGER, TARGET :: coarray(3)[*]
    coarray = 10*THIS_IMAGE()
    SYNC ALL
    IF (THIS_IMAGE() == 1) THEN
        SYNC ALL
        coarray = 123
        SYNC ALL
    ELSE IF (THIS_IMAGE() == 2) THEN
        CALL Fred(coarray(:)[1])
    ELSE
        SYNC ALL
        SYNC ALL
    END IF
CONTAINS
    SUBROUTINE Fred (arg)
        INTEGER, TARGET :: arg(:)
        PRINT *, arg
        SYNC ALL
        SYNC ALL
        PRINT *, arg
    END SUBROUTINE Fred
END PROGRAM Main


DISCUSSION:

This program is modifying an actual argument while it is associated
with a dummy argument.  That is normally prohibited by the anti-aliasing
rules in 12.5.2.13, but these do not operate in the TARGET dummy
argument case.  However, coindexed actual arguments are accessing
remote memory, so in general will be passed by copy-in/out; in this
case permitting aliasing is not reasonable.

ANSWER:

The program is not intended to be conforming.  Edits are provided to
correct this oversight.


EDITS:

[300] 12.5.2.13p1(3)(b) append to the end of the paragraph "or a
coindexed object".

[300] 12.5.2.13p1(4)(b) append to the end of the paragraph "or a
coindexed object".


SUBMITTED BY: Nick Maclaren


HISTORY: m205   14-223   Submitted
         m205   14-223r1 Revised example and discussion.

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