This also applies to PetscFree() On Feb 15, 2011, at 4:47 PM, Barry Smith 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

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);