[petsc-dev] Forward declarations of types?

[Jed Brown]

This package is pretty cool.

http://code.google.com/p/include-what-you-use/


On Fri, Feb 15, 2013 at 11:28 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> We currently use recursive includes everywhere, so petscdmda.h includes
> all of petscao.h just so it can declare DMDAGetAO and similar. Of course
> most users of (and implementation files in) DMDA do not reference AO so
> they don't need to know about all the AO functions.
>
> The normal approach to this is to forward-declare the type, so instead of
>
> #include <petscao.h> /* includes lots of other stuff */
> PETSC_EXTERN PetscErrorCode DMDAGetAO(DM,AO*);
>
> one would write
>
> typedef struct _p_AO *AO;
> PETSC_EXTERN PetscErrorCode DMDAGetAO(DM,AO*);
>
> in which case all three files in PETSc that actually call AO routines
> would need to include petscao.h. That is arguably a good thing since it
> makes the actual dependencies more explicit, and is recommended by many
> (mostly C++) style guidelines.
>
> Is this something worth considering? I think stuff like petscvec.h and
> petscmat.h ends up pretty much always being needed, but petscdm.h is only
> used by a handful of files in petscksp and above, for example.
>
> It might be nice to get rarely-used stuff like petscdraw.h out of
> petscsys.h.
>
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