J3/01-154r1

Date:    12-Apr-2001
To:      J3
From:    interp/Stan Whitlock
Subject: Interpretation 19 (Result of NULL intrinsic associated with
         CHARACTER(*) dummy argument)

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NUMBER: 000019
TITLE: Result of NULL intrinsic associated with CHARACTER(*) dummy argument
KEYWORDS: NULL intrinsic, assumed character length parameter,
          argument association, pointer association
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION: Consider the following program.

      PROGRAM P
        CALL SUB(NULL())
      CONTAINS
        SUBROUTINE SUB(C)
          CHARACTER(*), POINTER :: C

          PRINT *, LEN(C)
        END SUBROUTINE SUB
      END PROGRAM P

According to 7.1.4.1 [91:27-30], "The data type, type parameters and rank
of the result of the intrinsic function NULL when it appears without an
argument are determined by the pointer that becomes associated with the
result.  See Table 7.2."  In this case, the pointer that becomes associated
with the result is the corresponding dummy argument when the result appears
as an actual argument.

However, according to 5.1.1.5 [51:14-18], a dummy argument of type character,
with a character length parameter of *, "assumes the length of the
associated actual argument when the procedure is invoked."

Is this a standard conforming program?  If so, how is the length of C
determined, and what should be the output of this program?

ANSWER:

No, this program does not conform to the standard since the actual
argument does not have a character length for the dummy argument to
assume. The edit makes this clear.

EDIT:

Page 91, subclause 7.1.4.1, last line [91:41]. Add
    The optional argument shall also be present if the reference
    appears as an actual argument corresponding to a dummy argument
    with assumed character length.

SUBMITTED BY: Henry Zongaro

HISTORY: 98-148   m145 Submitted
         01-154r1 m156 Passed unanimously by J3 meeting