[petsc-dev] Why do we use void* instead of PetscObject in PETSc?

[Dave May]

On Mon, 4 Mar 2019 at 21:47, Jed Brown <jed at jedbrown.org> wrote:

> Dave May <dave.mayhem23 at gmail.com> writes:
>
> > On Mon, 4 Mar 2019 at 21:30, Jed Brown <jed at jedbrown.org> wrote:
> >
> >> If reusing, would the interface require
> >> casting the function pointers to void(*)(void) instead of what is
> >> currently type-safe for most function pointers?
> >
> >
> > No. I don't see that casting a function pointer would be required.
> > We would have
> >
> > SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode
> > (*J)(SNES,Vec,Mat,Mat,PetscObject),PetscObject ctx)
>
> Oh, the PetscObject would only contain the context, not the function
> pointer (at least not publicly).


Yes.


> What does user code look like?
>
>   PetscErrorCode f(..., PetscObject ctx) {
>     User user;
>     ierr =
> PetscContainerGetPointer((PetscContainer)ctx,&user);CHKERRQ(ierr);
>     ...
>   }
>

For most basic use-cases, yes exactly like that.
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