[petsc-dev] clang --analyze messages on PETSc

[Matthew Knepley]

On Tue, Apr 14, 2015 at 7:12 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Apr 14, 2015, at 6:13 PM, Matthew Knepley <knepley at gmail.com> wrote:
> >
> > On Tue, Apr 14, 2015 at 6:00 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > > On Apr 14, 2015, at 5:40 PM, Jed Brown <jed at jedbrown.org> wrote:
> > >
> > > Matthew Knepley <knepley at gmail.com> writes:
> > >> I really do not want that. I am especially unwilling to do that just
> to
> > >> appease static analysis.
> > >
> > > I think it's actually better for debuggability and
> > > strictness/normalization within the code, but we had this argument a
> > > year ago and if you still insist, I'm not going to dig it up.
> >
> >   But I did. So Matt's argument is that having a pointer you are not
> allowed to use be anything but NULL is dangerous because it could be used
> wrong and no one would know.
> >
> >    BTW how come all the code  (!(m1) ? (*(r1) = 0,0) : 0)  stuff uses 0
> instead of NULL? Wouldn't it be clearer to use NULL when one means NULL?
> >
>    I understand what you wrote below. My question is why there are a bunch
> of symbols 0 in the PetscMalloc() macros; shouldn't they be NULL for
> clarity.
>
>     0.0  for float, 0 for integer, and NULL for pointer?  That's all.


I am fine for NULL. I was just using 0 since its equivalent and short.

  Matt


> > I am arguing for uniformity. With the current system, all internal PETSc
> mallocs (we are supposed to use PetscMallocK everywhere)
> > will return NULL for 0 size argument. On the other hand, if you just
> forward the request to malloc, the standard says it can return
> > a valid pointer OR NULL, so now we have different behavior. What is
> worse is that this "valid" pointer can be freed, but it cannot
> > be dereferenced, and there is no way to determine that it cannot be
> dereferenced, unlike NULL. I see absolutely no good argument
> > for this situation.
> >
> >    Matt
> >
> >
> >   Barry
> >
> >
> >
> >
> >
> > --
> > 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
>
>


-- 
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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