Re: signed vs. unsigned in TYPEALIGN (was Re: space reserved for WAL record does not match what was written: panic on windows)

On Fri, Oct 18, 2013 at 12:10:17AM +0200, Andres Freund wrote:
> On 2013-10-17 18:04:34 -0400, Noah Misch wrote:
> > On Thu, Oct 17, 2013 at 08:27:01PM +0200, Andres Freund wrote:
> > > On 2013-10-17 12:33:45 -0400, Noah Misch wrote:
> > > > > 1. Is there any guarantee that sizeof(intptr_t) >= sizeof(size_t)?
> > > > > (Note that Size is just a typedef for size_t, in c.h)
> > > >
> > > > C99 doesn't require it, but I have never heard of a platform where it is
> > > > false. sizeof(intptr_t) > sizeof(size_t) systems have existed.
> > >
> > > Either way, both have to be at least 4byte on 32bit platforms and 8byte
> > > on 64bit ones. So I as well think we're good.
> >
> > C99 does not have concepts like "32bit platform" and "64bit platform", so it
> > cannot make such a constraint. Nonetheless, I agree we're good with respect
> > to implementations actually worth anticipating.
>
> But afaik we indirectly require either 4 or 8 byte pointers or in
> configure. And we have a requirement for non-segmented memory afaics. So
> both size_t and intptr_t have to be big enough to store a pointer. Which
> in turn implies that they have to be at least 4/8 bytes.

Conformance is possible in an implementation with 8-byte size_t and 4-byte
pointers. Filling in the details makes for a decent party game.

> > Having said that, changing the ancient macros to use uintptr_t does have the
> > advantage you mention, and I'm failing to think of a disadvantage.
>
> +1

Committed that way, then.

--
Noah Misch
EnterpriseDB http://www.enterprisedb.com