J3/01-134

Date:     13 February 2001
To:       J3
From:     Van Snyder
Subject:  Minor defect in definition of "present"

NUMBER: ?
TITLE: Definition of "present" is defective
KEYWORDS: present, dummy argument
DEFECT TYPE: loophole?
STATUS: J3 consideration in progress

DISCUSSION

Subclause 12.4.1.5 begins with a definition of the term "present":

"A dummy argument is present in an instance of a subprogram if it is
associated with an actual argument and the actual argument either is a
dummy argument that is present in the invoking scoping unit or is not a
dummy argument of the invoking scoping unit."

This is defective in that if the actual argumement is a dummy argument
that is accessed by host association, it is not a dummy argument OF the
invoking scoping unit, and therefore although it may be "not present" in
the procedure of which it is a dummy argument, it is nonetheless
"present" in an internal procedure of that procedure.

EXAMPLE:

  module M
  contains
    subroutine S1 ( A )
      integer, optional :: A
      call S11
    contains
      subroutine S11
        call S12 ( A )
      end subroutine S11
      subroutine S12 ( B )
        integer, optional :: B
        if ( present(B) ) print *, 'B is present'
      end subroutine S12
    end subroutine S1
  end module M

  program P
    use M, only: S1
    call S1
  end program P

According to the above-cited definition, this program ought to print

  B is present

because the dummy argument B of S12 is associated with an actual argument
A that is not a dummy argument of the invoking scoping unit S11.

EDITS:

In the third line of subclause 12.4.1.5 [202:45 in 97-007r2], either
replace "of" by "in" or delete "of the invoking scoping unit".

SUBMITTED BY: Van Snyder
HISTORY: 01-134 m156 Submitted