(j3.2006) request for interpretation

[Van Snyder]

On Mon, 2008-03-31 at 14:05 -0500, Bill Long wrote:
> 
> Robert Corbett wrote:
> > Consider the following program
> >
> >        MODULE M1
> >          INTERFACE SUBR
> >            MODULE PROCEDURE SUBR1
> >          END INTERFACE
> >        CONTAINS
> >          SUBROUTINE SUBR1
> >          END SUBROUTINE
> >        END
> >
> >        MODULE M2
> >          INTERFACE SUBR
> >            MODULE PROCEDURE SUBR2
> >          END INTERFACE
> >        CONTAINS
> >          SUBROUTINE SUBR2
> >          END SUBROUTINE
> >        END
> >
> >        PROGRAM MAIN
> >          USE M1
> >          CALL S
> >        CONTAINS
> >          SUBROUTINE S
> >            USE M2
> >            CALL SUBR
> >          END SUBROUTINE
> >        END
> >
> > Is this program standard conforming?
> >   
> 
> I tried three compilers and they all said it is not. All gave compile 
> time errors that the generic interface for SUBR in subroutine S had 
> indistinguishable specifics.
> 
> > The program appears to violate the restrictions set out
> > in Section 16.2.3 of the Fortran 2003 standard.  
> 
> Right.
> 
> 
> > It has
> > been argued that Section 12.4.4.1 of the Fortran 2003
> > standard modifies the requirements of Section 16.2.3.
> >   
> 12.4.4.1 says things like  "The rules in 16.2.3 ensure that there can be 
> at most one such specific procedure."
> 
> > While that might have been what was intended, I do not
> > see how the text of Section 12.4.4.1 has any effect on
> > the requirements of Section 16.2.3.
> >   
> 
> Agreed.
> 
> I think the more relevant citation is 12.4.4 (1) (d) that says "A 
> procedure name is established to be generic in a scoping unit if that 
> scoping unit contains no declarations of that name, that scoping unit 
> has a host scoping unit, and that name is established to be generic in 
> the host scoping unit."   The point just above in (1)(c) explains how 
> generic names become visible through a USE statement. 
> 
> The general concept that multiple, visible generic interfaces with the 
> same name effectively merge together their lists of specifics is pretty 
> fundamental in Fortran.  Trying to come up with some exceptions to that 
> concept just to make the program above standard conforming seems like 
> the wrong path.

A statement like IMPORT, EXCEPT: <exclude-list> would solve this
problem.  But... IMPORT is to be allowed only in interface bodies.

> Cheers,
> Bill
> 
> 
> > Robert Corbett
> > _______________________________________________
> > J3 mailing list
> > J3 at j3-fortran.org
> > http://j3-fortran.org/mailman/listinfo/j3
> >   
>