[petsc-users] [Fortran] subroutines inside modules?

[Stephan Kramer]

On 30/09/10 23:09, Leo van Kampenhout wrote:
> Declaring it external in the program/subroutine that is using the module
> results in
>
> main.F:65.43:
>        external gridtest
> Error: Cannot change attributes of USE-associated symbol at (1)
>
> Thanks, Leo

Yes, as I said before :) - module subroutines should *not* be declared external. You do
not need that line.

Cheers
Stephan


>
>
> 2010/9/30 Stephan Kramer <s.kramer at imperial.ac.uk
> <mailto:s.kramer at imperial.ac.uk>>
>
>     On 30/09/10 15:31, Leo van Kampenhout wrote:
>
>         Hi all,
>
>         since it is mandatory to declare all subroutines as "external" in
>         Fortran, is it possible for Modules to have subroutines? I'm
>         unable to
>         declare the subroutine external inside the module itself, nor in the
>         program which is using it. Not declaring it external at all
>         results in
>         the following compilation error:
>
>         /net/users/csg/csg4035/master/workdir/src/main.F:97: undefined
>         reference
>         to `__grid_MOD_readgrid'
>
>         (the module is here is named "grid", the subroutine "readgrid" )
>
>         Thanks,
>         Leo
>
>
>     If you put your subroutine in a module, it should not be declared
>     external. You can directly call it from within the module itself. When
>     calling it inside any other module/program you need to add "use
>     grid" before
>     the "implicit none".
>
>     Putting subroutines inside a module is highly recommended as it
>     automatically
>     provides an explicit interface so that the compiler can check the
>     arguments in
>     your subroutine call.
>
>     Cheers
>     Stephan
>
>