(j3.2006) C-Interop question about establishing the bounds

[Bill Long]

On Feb 6, 2015, at 2:36 PM, Daniel C Chen <cdchen at ca.ibm.com> wrote:

> Hello, 
> 
> Please consider the following code:
> 
>       Program main
>         interface
>           subroutine sub(c_arg) bind(c)
>             integer n                   !! Local auto var
>             character(*) :: c_arg(n,5)
>           end subroutine
>         end interface
>         character(3) :: ccc(10)
>         call sub(ccc)
>       end program
> 
> Question: 
> 1. Is the program standard conforming?
> 2. If it is legal, what would be the rank of the effective argument that is passed to sub?
> 3. If it is legal, what would be the ubound of the effecive argument? 
> 
> Discussion: 
> I found the following statement [99:5-9, 5.3.8.2p2].
> 
> "An explicit-shape array that is a named local variable of 
> a subprogram or BLOCK construct may have bounds that are not 
> constant expressions. The bounds, and hence shape, are 
> determined on entry to a procedure defined by the subprogram, 
> or on execution of the BLOCK statement, by evaluating 
> the bounds? expressions."
> 
> Does it mean in order to determine the bounds of c_arg on entry to sub, 
> 'n' must be a dummy argument itself since 'n' may not be defined at the
> Entry to sub if it is automatic variable?

A variable used as part of a dimension in this case has to be a dummy argument, accessible from a module, or part of a visible COMMON block.  The value has to be known on entry to the routine.   See the full set of restrictions (including those for BLOCK) in 7.1.11 Specification expressions.

Cheers,
Bill




>  
> How does it apply to the BLOCK statement?
> 
> 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
> 
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Bill Long                                                                       longb at cray.com
Fortran Technical Suport  &                                  voice:  651-605-9024
Bioinformatics Software Development                     fax:  651-605-9142
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