J3/14-218r2
To:      J3
From:    Nick Maclaren & Malcolm Cohen
Subject: ASYNCHRONOUS and argument passing
Date: 2014 October 15

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NUMBER: F08/0115
TITLE: ASYNCHRONOUS and argument passing
KEYWORD: ASYNCHRONOUS
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider

  PROGRAM Main
    INTEGER, ASYNCHRONOUS :: array(5) = -1
    OPEN (11, FILE='junk', ASYNCHRONOUS='yes', ACTION='read')
    CALL async_read(array)
    CALL fred(array(::2)) ! Problematic?
    WAIT (11)
    PRINT *, array
  CONTAINS
    SUBROUTINE async_read(array)
      INTEGER, ASYNCHRONOUS, INTENT(INOUT) :: array(:)
      READ (11, *, ASYNCHRONOUS='yes') array
    END SUBROUTINE
  END PROGRAM
  SUBROUTINE Fred (arg)  ! In general, an external procedure
    INTEGER :: arg(*)    ! Otherwise unused
    CONTINUE             ! In general, something that takes more time
  END SUBROUTINE

Is the call to "Fred" standard-conforming?

It is not excluded by 5.3.4p2, because 'array' is merely associated
with 'arg' in subroutine Fred, and not used in any executable
statement or specification expression there.  However, if copy-in/out
is used for argument passing and the actual i/o transfer occurs in
between the copy-in and copy-out, the wrong answers will be given.

ANSWER:

This program was not intended to be conforming.  An edit is provided
to correct this oversight.

EDITS:

[90:15] 5.3.4 ASYNCHRONOUS attribute, p2, first bullet,
        between "the variable" and "appears"
        insert "is a dummy argument or".

SUBMITTED BY: Nick Maclaren


HISTORY: 14-218    m205  Submitted
         14-218r1  m205  Revised
         14-218r2  m205  Further Revised

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