[petsc-dev] XXXDestroy() mistaken design in PETSc

[Matthew Knepley]

On Tue, Feb 15, 2011 at 4:47 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>  In MPI one calls MPI_Comm_free(&comm) to allow the MPI implementation to
> set the pointer explicitly to 0 after the object is destroyed.
>
>  In Petsc XXXDestroy() does not pass the pointer (because it seemed too
> unnatural to me in 1994) thus not allowing 0ing the pointer.
>
>   Was this a bad design decision? Should it be revisited?
>
>   Barry
>
>  Two use cases
>
> 1) error detection when someone tries to reuse a freed object
>

We catch this with other error detection. I do not think we would gain much
here.


> 2) when removing some objects from a data structure that will be used data
> one currently needs to do
>
>  XXXXDestroy(mystruct->something);CHKERRQ(ierr); mystruct->something = 0;
>
> instead of the cleaner XXXDestroy(&mystruct->something);CHKERRQ(ierr);


True, but again I do not think the win is large.

   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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