[J3] Is this standard-conforming?

[Steidel, Jon L]

I have access to an older NAG compile (6.1) which compiled and ran this and printed "goodbye".

-jon

-----Original Message-----
From: Bill Long [mailto:longb at cray.com] 
Sent: Thursday, July 26, 2018 4:16 PM
To: Steidel, Jon L <jon.l.steidel at intel.com>
Cc: General J3 interest list <j3 at mailman.j3-fortran.org>
Subject: Re: [J3] Is this standard-conforming?

I tried 4 compilers, and one accepted and ran the program (Intel), but the other 3 produced errors at compile time.


> On Jul 26, 2018, at 2:54 PM, Steidel, Jon L <jon.l.steidel at intel.com> wrote:
> 
> I'm not sure I see a difference between and IMPORT of a type or a named constant in a function interface body and the USE association of the type or the named constant.  
> 
> Consider
> 
> module mod
> 
>  character(len=5), parameter :: d_name="d_foo"
> 
> end module
> 
> program main
>   implicit none
> 
>  character(len=5), parameter :: c_name="c_foo"
> 
>  interface
>    subroutine foo() bind(C,name=c_name)
>      use mod, c_name => d_name
>  !    import c_name
>    end subroutine
>  end interface
> 
>  call foo()
> 
> end  program
> 
> subroutine foo_c () bind (C, name="c_foo")
>   print *, "hello"
> end
> 
> subroutine foo() bind (C, name="d_foo")
>   print *, "goodbye"
> end
> 
> Two compilers I have tried accept this and print "goodbye".  
> 
> -jon
> 
> 
> -----Original Message-----
> From: J3 [mailto:j3-bounces at mailman.j3-fortran.org] On Behalf Of Bill Long via J3
> Sent: Thursday, July 26, 2018 2:38 PM
> To: General J3 interest list <j3 at mailman.j3-fortran.org>
> Cc: Bill Long <longb at cray.com>
> Subject: Re: [J3] Is this standard-conforming?
> 
> Thanks, Dan, for looking this up. At least by m218 the /INTERP subgroup should be back in business.  
> 
> I should note that there IS a way around this for a function type. Instead of 
> 
>    type(ugg) function foo()
> 
> you can write
> 
>    function foo()  result(res)
>      import ugg
>      type(ugg) :: res
> 
> In the second case there is no room for ambiguity because the use of ugg is in the specification part of the function which is clearly covered by the import statement.  However, the standard still permits the first version, hence the need for compilers to implement a limited look-ahead capability. 
> 
> 
> Cheers,
> Bill
> 
> 
>> On Jul 26, 2018, at 1:12 PM, Dan Nagle via J3 <j3 at mailman.j3-fortran.org> wrote:
>> 
>> Hi,
>> 
>>> On Jul 26, 2018, at 10:23 , Bill Long via J3 <j3 at mailman.j3-fortran.org> wrote:
>>> 
>>> Similar to your case, the import of ugg  from the host occurs on the statement after the one where ugg is used.  In the case of a type definition like this there is no practical alternative, so compilers have been taught to ‘look ahead’ for a type definition.   I suspect we intended to allow the case you described, but the vendors did not anticipate needing to do a look-ahead for anything other that the function type.   If Malcolm disagrees about the intent, I’m ok with that.   I think it boils down to whether the FUNCTION statement itself is part of the scoping unit of the function. 
>>> 
>> 
>> And indeed, this is the oldest interpretation request in the file.
>> The issue has been argued, and the argument accepted, both ways.
>> 
>> --
>> 
>> Cheers!
>> Dan Nagle
>> 
>> 
> 
> Bill Long                                                                       longb at cray.com
> Principal Engineer, Fortran Technical Support &   voice:  651-605-9024
> Bioinformatics Software Development                      fax:  651-605-9143
> Cray Inc./ 2131 Lindau Lane/  Suite 1000/  Bloomington, MN  55425
> 
> 

Bill Long                                                                       longb at cray.com
Principal Engineer, Fortran Technical Support &   voice:  651-605-9024
Bioinformatics Software Development                      fax:  651-605-9143
Cray Inc./ 2131 Lindau Lane/  Suite 1000/  Bloomington, MN  55425