[petsc-dev] XXXGetContext() in Fortran

[Jed Brown]

On Wed, Nov 9, 2011 at 12:52, Barry Smith <bsmith at mcs.anl.gov> wrote:

> So what both Satish's and Ethan's email are saying is so long as you tell
> the Fortran function the interface that shows the type being returned you
> can "trick" the Fortran into thinking that data type is just coming from
> another Fortran routine.
>
>   I think this should resolve your issues and everything should be
> straightforward (no need for transfer function). Please let us know if this
> is problematic.
>

Thanks everyone. This works, and in hindsight, I should have looked at
snes/examples/tutorials/ex5f90.F because it does this with
SNESGetApplicationContext.

The unfortunate thing is that it appears that the user needs to write a
custom interface for each such function in order to get the compiler to
pass the pointer in a useful way. Is there a way for us to put some
interface definitions into the library? An (ugly) alternative would be to
provide some CPP macros that the user can use to get interface definitions
without needing to hand-type it (they would pass in their user-defined
type).

How can we manage multiple contexts with different types in the same file?
It looks like perhaps I can put the interface definitions in different
modules, which I can import at subroutine granularity. If I want to get the
context out of two MatShells inside the same function, I would have to
write helper functions so that they can import different interface
definitions via different modules?
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