(j3.2006) Question about submodule using its ancestor modue

[Bill Long]

I agree with Daniel that USE association is supposed to override HOST association.  However, then consider a modified case:

module m1
  interface 
     module subroutine sub(n)
        integer :: n
      end subroutine sub
  end interface
end module m1

module m2
  use m1
end module m2

submodule (m1) foo 
  use m2

contains

  module subroutine sub(n)
    integer :: n
    n = n + 1
  end subroutine sub

end submodule foo


and the constraint on the name of a submodule procedure:

 C1271  (R1239) The procedure-name shall have been declared to be a separate module procedure in the containing
                            program unit or an ancestor of that program unit.


SUB is declared to be a separate module procedure in module m2, but m2 is not an ancestor of submodule foo.  All entities in m1 are blocked in foo from host association because of the USE of m2.   If we?re OK with the idea that the declaration of the separate module procedure can come from a module that is not an ancestor of the submodule containing the implementation, then this code is OK.  But I don?t think that is what C1271 is intended to say.

Cheers,
Bill






On Nov 19, 2014, at 10:03 AM, Daniel C Chen <cdchen at ca.ibm.com> wrote:

> I agree with Reinhold that the code should be conforming. However, I think the use association should override the host association. It should have the same effect as
> Program main
>   Use m
> Contains
>   Subroutine sub()
>     Use m
>   End 
> End :
> 
> Thanks,
> 
> Daniel
> 
> XL Fortran Development - IBM Toronto Software Lab
> Phone: 905-413-3056   
> Tie: 969-3056   
> Email: cdchen at ca.ibm.com
> http://www.ibm.com/software/awdtools/fortran/xlfortran
> 
> <graycol.gif>"Bader, Reinhold" ---11/19/2014 04:03:38---Hello Bill,  my take is that the code is conforming, and that host association overrides
> 
> From:	"Bader, Reinhold" <Reinhold.Bader at lrz.de>
> To:	fortran standards email list for J3 <j3 at mailman.j3-fortran.org>
> Date:	11/19/2014 04:03
> Subject:	Re: (j3.2006) Question about submodule using its ancestor modue
> Sent by:	j3-bounces at mailman.j3-fortran.org
> 
> 
> 
> Hello Bill, 
> 
> my take is that the code is conforming, and that host association overrides
> use association in this context. Because the module must anyway be compiled 
> before the submodule is, there doesn't appear to be a circularity problem.
> I don't think ambiguities can arise (consider the analogous case
> 
> m1 uses b
> m2 uses b
> a uses m1 and m2
> ).
> 
> The case of indirect referencing is actually the interesting use case: Say you have
> an abstract type in m1. This will typically be extended in some other 
> module m2, which needs to use m1. On the other hand, for full dependency
> inversion, m1 needs to provide e.g. a procedure to create an object. This often 
> will imply that the complete inheritance tree must be dealt with, i.e. the procedure
> specifically needs type information stored in m2. Hence, to avoid circular module
> references, the procedure needs to be put into a submodule, which uses m2, and therefore 
> indirectly also m1.
> 
> Cheers
> Reinhold
> 
> 
> > -----Urspr?ngliche Nachricht-----
> > Von: j3-bounces at mailman.j3-fortran.org [mailto:j3-bounces at mailman.j3-
> > fortran.org] Im Auftrag von Bill Long
> > Gesendet: Mittwoch, 19. November 2014 00:06
> > An: fortran standards email list for J3
> > Betreff: (j3.2006) Question about submodule using its ancestor modue
> > 
> > 
> > Is the USE statement in the submodule below conforming?
> > 
> > module m1
> >   real :: x
> > end module m1
> > 
> > submodule (m1) bar
> >   use m1
> > end submodule bar
> > 
> > Option 1: It is OK, since the USE of m1 in the submodule blocks all host
> > association of objects in module m1, so no ambiguity.
> > 
> > Option 2: No. The submodule is an extension of m1 and this amounts to a
> > recursive access to the module.
> > 
> > 
> > I suspect Option 2 would promote better code and fewer mistakes. Particularly if
> > "use m1" were instead "use m2" where m2 included a USE of m1.
> > 
> > 
> > Cheers,
> > Bill
> > 
> > 
> > Bill Long                                                                       longb at cray.com
> > Fortran Technical Suport  &                                  voice:  651-605-9024
> > Bioinformatics Software Development                     fax:  651-605-9142
> > Cray Inc./ Cray Plaza, Suite 210/ 380 Jackson St./ St. Paul, MN 55101
> > 
> > 
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Bill Long                                                                       longb at cray.com
Fortran Technical Suport  &                                  voice:  651-605-9024
Bioinformatics Software Development                     fax:  651-605-9142
Cray Inc./ Cray Plaza, Suite 210/ 380 Jackson St./ St. Paul, MN 55101