J3/10-236
To: J3
From: Malcolm Cohen
Subject: Generic resolution and intrinsic procedures
Date: 2010 October 11

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NUMBER: F08/0006
TITLE: Generic resolution, intrinsic procedures, and host association
KEYWORDS: intrinsic, generic, host association
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

The specifications of some intrinsic functions and subroutines
explicitly ban certain combinations of arguments, even though those
combinations are included in the title and the argument portion of the
specification of the function or subroutine.  Examples include CMPLX
and RANDOM_SEED.  Other requirements include being a valid KIND type
parameter value (e.g. INT) or having having character length 1
(e.g. ICHAR).

Consider the program fragment

  PROGRAM p
    INTERFACE cmplx
      LOGICAL FUNCTION mycmplx(a,b)
        COMPLEX a,b
      END
    END INTERFACE
    INTERFACE random_seed
      SUBROUTINE my_random_seed(get,put,size)
        INTEGER,OPTIONAL :: get(:),put(:),size
      END SUBROUTINE
    END INTERFACE
    INTERFACE int
      INTEGER FUNCTION myint(i,j)
      END
    END INTERFACE
    COMPLEX :: z = (1,2)
    REAL :: r = 3
    CALL check
  CONTAINS
    SUBROUTINE check
      INTRINSIC int,cmplx,random_seed
      PRINT *,cmplx(z,r)            ! Reference (1).
      CALL random_seed(GET=a,PUT=b) ! Reference (2).
      PRINT *,int(3,17)             ! Reference (3).
    END SUBROUTINE
  END PROGRAM

Are the procedure references (1), (2), and (3) invalid references to
the intrinsic procedures CMPLX, RANDOM_SEED, and INT, or are they
valid references to the user procedures mycmplx, my_random_seed, and
myint respectively?

ANSWER:

Reference (1) is a valid reference to the user procedure.

Both references (2) and (3) are invalid references to the intrinsic
procedures; however, no constraints are violated so a standard-
conforming processor may do anything, including treating them as
references to the user procedures.

DISCUSSION:

12.5.5.2 paragraph 4 explains that the reference is to the intrinsic
procedure if it is "consistent with the interface of that intrinsic
procedure".  The interface to an intrinsic procedure consists of its
name, characteristics, and dummy argument names.  The characteristics
of a procedure as defined by 12.4.1 do not include arbitrary
restrictions such as those for RANDOM_SEED which are on argument
presence (an execution time concept).  Nor are requirements such as an
actual argument being required to be a constant expression part of an
interface.

In the case of CMPLX however, there is no specific version whose
interface has an X argument of type COMPLEX and any Y argument.
13.7.36 describes this by "If X is of type complex, no actual argument
shall correspond to Y".  Therefore the reference to CMPLX with such
arguments is not consistent with the intrinsic.

EDITS to 10-007:

None.

SUBMITTED BY: Robert Corbett

HISTORY: 10-153    m192  F08/0006 submitted
         10-153r1  m192  Draft answer
         10-153r2  m192  Revised answer - Passed by J3 meeting
         10-202    m192  Amended by J3 letter ballot 10-199; failed
                         J3 letter ballot 10-199
         10-nnn    m193  Revised answer.

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