Re: Q: void* vs. unsigned long
H. Peter Anvin (hpa@transmeta.com)
16 Feb 1999 05:00:24 GMT
Followup to: <36C8F5B0.6D56F88D@quark.vpplus.com>
By author: Brian Gerst <bgerst@quark.vpplus.com>
In newsgroup: linux.dev.kernel
> >
> > I'm curious about the mixed use of void* and unsigned long in the kernel to
> > represent addresses (as in tqueue.h vs. timer.h). Is it simply a case of
> > author preference, or is it subtle semantics for the case where a datam is
> > most likely an integer value but _could_ also be a pointer? Or is it more
> > complicated? With the future in mind, what is recommended to budding
> > kernel hackers?
>
> sizeof (void *) == sizeof (unsigned long) if and only if you are on a
> 32-bit arch, like i386. The only place unsigned long should be used is
> in arch specific code, and even then it's use should not be encouraged.
> If such code exists in the general kernel (device drivers, file systems,
> etc.) then it is severely broken from a portability standpoint and will
> not work on 64-bit arches.
>
Actually, it will. sizeof(unsigned long) == sizeof(void *) == 8 on
64-bit architectures.
-hpa
--
"Linux is a very complete and sophisticated operating system. There
are, and will be, large numbers of applications available for it."
-- Paul Maritz, Group Vice President for Platforms And Applications,
Microsoft Corporation [Reference at: http://www.kernel.org/~hpa/ms.html]
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