Re: [PATCH 4/5] altstack: Don't use 0 pointer literals

Thank you, both.  I'll return to the fold and use NULL, as seems right and
proper.

On Thu, Jun 16, 2016 at 7:12 AM David Gibson <[email protected]>
wrote:

> On Tue, Jun 14, 2016 at 01:45:10PM +0930, Paul 'Rusty' Russell wrote:
> > Dan Good <[email protected]> writes:
> > > Hi David,
> > >
> > > I'm back home in front of a real keyboard, and want to follow up with
> you
> > > about your patches.  I must admit that my usual practice is to use
> NULL,
> > > and not 0.  Around the time I wrote altstack I had recently read Jen
> > > Gustedt's book, Modern C.  In it, he makes the point that NULL hides
> more
> > > than it clarifies (see section 11.7).
> >
> > (I don't really care: your code, your style).  But...
> >
> > He is so horrifically wrong, it's amazing.
> >
> > Section 7.17 is loosened from ANSI C which said NULL was 0, presumably
> > to *allow* compilers to avoid the varargs issue.  A compiler *could* do
> > insane shit to make that problem even worse, but you would never use
> > such a compiler.  There are other legal-but-insane things a compiler can
> > do, too, and the answer is the same; real code won't work, nobody else
> > cares.
> >
> > OTOH, using 0 in place of NULL makes for much more potential type order
> > confusion.  Not to mention confusing every damn C programmer on the
> > planet.
>
> Yeah.  I can kind of see the hint of a good idea in those articles,
> but on balance they're really not convincing.  Basically, as Rusty
> says, matching the conventions of the huge bulk of existing C code
> outweighs the value of working with a compiler/library that has gone
> out of its way to implement this stupidly.
>
> > Note, I also assume NULL is all zero-bits,
>
> I try to avoid that one, although I can't be sure I always have - I'm
> not sure, but I think one of the s390 variants might break this.
>
> > that size_t can hold a
> > ptrdiff_t,
>
> Dunno if I've assumed that much.
>
> > and that a pointer to a function which takes a type *
> > argument can be cast and called as a function which takes a void *.
>
> Yeah, I've used that.
>
> > If someone ports CCAN to a platform where those are not true, I'd be
> > fascinated...
>
> --
> David Gibson                    | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_
> _other_
>                                 | _way_ _around_!
> http://www.ozlabs.org/~dgibson
>

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