[petsc-dev] Problem with PETSC_NULL and variadic functions

[Dmitry Karpeev]

On Wed, Nov 9, 2011 at 3:34 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Nov 9, 2011, at 3:30 PM, Matthew Knepley wrote:
>
> > On Wed, Nov 9, 2011 at 9:28 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> > On Wed, Nov 9, 2011 at 15:22, Matthew Knepley <knepley at gmail.com> wrote:
> > So the problem is that in C++, when using a variadic function, you
> cannot type PETSC_NULL directly into the argument list? When would you ever
> > do this? If an argument to Printf() is equal to PETSC_NULL, no problem.
> Its only when PETSC_NULL is passed directly. Why not prevent that in
> > all PETSc variadic functions, which I think are only the prints.
> >
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeScatter(DM,Vec,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeGather(DM,Vec,InsertMode,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeGetAccess(DM,Vec,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeRestoreAccess(DM,Vec,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeGetLocalVectors(DM,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeGetEntries(DM,...);
> > include/petscdmcomposite.h:extern PetscErrorCode
> DMCompositeRestoreLocalVectors(DM,...);
>
>
> > Yes, I am in favor of getting rid of all variadic functions and
> replacing them with array arguments.
>
>    Actually with the redesign where everything is a DM that becomes
> possible I think. Though a little ugly.
>

In my opinion adding a format string is actually an acceptable solution,
given all of the complications we have
discussed here.  Using array arguments means the user has to do explicit
memory management of those args,
not to mention the overhead for each call.

Dmitry.

>
>   Barry
>
> >
> >    Matt
> >
> > --
> > What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> > -- Norbert Wiener
>
>
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