[J3] [EXTERNAL] Re: surprisingly PURE

[Van Snyder]

On Sun, 2020-04-19 at 15:16 -0400, Steve Lionel via J3 wrote:
> I admit that I am not all that good as a language lawyer, but I think 
> Steve K has it right.
> 
> C1594 says (with irrelevant parts removed):
> 
> In a pure subprogram any designator with a base object that is in common 
> or accessed by host or use association,...  or an object that is storage 
> associated with any such variable, shall not be used
>   (1) in a variable definition context (19.6.7),
> 
> My reading here is that Y%P is an object that is storage associated with 
> X, which is accessed by host association, and therefore Y%P shall not be 
> used in a variable definition context.
> 
> I welcome other viewpoints.

Y%P is pointer associated, not storage associated.

> 
> Steve L
> 
> 
> On 4/18/2020 9:31 PM, Robert Corbett via J3 wrote:
> > I assume you mean C1594 (1).
> >
> > No part of C1594 applies to
> > this example.  The variable Y is
> > a local variable of SUBR.  The
> > variable Y does not satisfy any
> > of the conditions listed at the
> > start of C1594.
> >
> > Robert Corbett
> >
> >> On Apr 18, 2020, at 4:38 PM, Steven G. Kargl <kargl at troutmask.apl.washington.edu> wrote:
> >>
> >>> On Sat, Apr 18, 2020 at 11:12:27PM +0000, Robert Corbett via J3 wrote:
> >>>        REAL, TARGET :: X = 1.0
> >>>        TYPE T
> >>>          REAL, POINTER :: P => X
> >>>        END TYPE T
> >>>        CALL SUBR
> >>>        PRINT *, X
> >>>        CONTAINS
> >>>          PURE SUBROUTINE SUBR
> >>>            TYPE(T) Y
> >>>            Y%P = 2.0
> >>>          END SUBROUTINE SUBR
> >>>        END
> >>> -------------------------------
> >>>
> >>> I think the program given above is standard conformant.
> >>> If it is not standard conformant, please let me know
> >>> why it is not.  I know that it should not be standard
> >>> conformant, but I see no reason it is not.
> >>>
> >>> The key point here is that default component
> >>> initialization does not give the variable the SAVE
> >>> attribute.  If Y had the SAVE attribute, the program
> >>> would not be conformant.
> >>>
> >>> This program is my third attempt to show this problem.
> >>> My first program was not conformant, and my second did
> >>> not properly demonstrate the problem.
> >>>
> >> Doesn't f2018:C1593(1) apply?  I admit I have troubling reading
> >> this section of the Fortran standard.
> >>
> >> -- 
> >> Steve
> 
>