PCShellSetContext fortran interface

[Barry Smith]

  Stephan,

    Even from Fortran the context is treated as a memory address, not
an integer value. You could use a common block (yuck) or some array that
is alloacated higher in the stack as the context, but as you note you
cannot use a local variable.

    Barry

You could argue that we should have implemented the way you suggest as 
only allow an integer value, but I would respond that in Fortran 90 one
can pass in address of derived types, allocated arrays etc so I prefer our
current design.


On Thu, 7 Jun 2007, Stephan Kramer wrote:

> Hi,
> 
> I don't know if this is the expected behaviour but calling PCShellSetContext 
> from fortran, the thing that is stored is not the integer value of context, 
> but the pointer to this integer. Thus problems arise when supplying an 
> integer variable that goes out of scope (e.g. on the stack) inbetween 
> PCShellSetContext and the call to the 'apply shell preconditioner' routine. I 
> know this makes sense from the C point of view, where you are merely 
> supplying a void pointer, but this is not what you expect in Fortran were the 
> only use of context could be as a reference/index itself to another object, 
> and you thus expect the value of context to be stored.
> 
> Cheers
> Stephan Kramer
> 
>