On Tue, Apr 14, 2015 at 7:12 PM, Barry Smith <bsm...@mcs.anl.gov> wrote:
> > > On Apr 14, 2015, at 6:13 PM, Matthew Knepley <knep...@gmail.com> wrote: > > > > On Tue, Apr 14, 2015 at 6:00 PM, Barry Smith <bsm...@mcs.anl.gov> wrote: > > > > > On Apr 14, 2015, at 5:40 PM, Jed Brown <j...@jedbrown.org> wrote: > > > > > > Matthew Knepley <knep...@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
