[petsc-dev] removing PETSC_NULL?

[Matthew Knepley]

On Wed, Feb 6, 2013 at 9:33 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Wed, Feb 6, 2013 at 7:35 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>    In 1994 NULL was a pain because for different systems it was in
>> different include files and sometimes you had to do very nasty stuff like
>>
>> #if !defined(NULL)
>> #define NULL  0
>>
>> This is why PETSC_NULL came into existence.
>>
>> Is the world a different place now? Based on the fact there are numerous
>> (272 to be exact thanks to Karl) uses of NULL in PETSc today and they seem
>> to cause absolutely no grief? (Except to Barry's tidy little mind) it seems
>> PETSC_NULL is not needed any longer?
>>
>>    If this is the case I propose we eradicate PETSC_NULL replacing it
>> everywhere with NULL.
>>
>
> We had a similar discussion a while back.
>
> http://lists.mcs.anl.gov/pipermail/petsc-dev/2011-November/006315.html
>
> Using NULL instead of PETSC_NULL does not help to safely pass a null
> pointer value to a variadic function, but PETSC_NULL is also unsafe.
>
> Note that nearly all instances of 'NULL' are in either sieve (disabled by
> default), examples, or pretty new code. (It's even possible that there were
> zero occurrences in critical library back when we had that thread.)
> However, there are certainly a few instances now and we've received no
> mail, so I'm also in favor of replacing PETSC_NULL with NULL.
>
> It's C89 after all, so as long as we are sure to include stddef.h, we
> should be fine.
>

I don't mind removing it, although the Fortran people still have to use
something else.

   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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