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

[Barry Smith]

  What about 

extern PetscErrorCode  VecDestroy_(Vec);
#define VecDestroy(a)  (VecDestroy_(a) || (((a) = 0),0))

  Not exactly PETSc style, but allows the switch without changing the API.

   Barry

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);