Date: Wed, 16 Sep 1998 23:52:16 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, gibbs@plutotech.com Cc: current@FreeBSD.ORG, Don.Lewis@tsc.tdk.com Subject: Re: New kernel compile warnings with CAM Message-ID: <199809161352.XAA07659@godzilla.zeta.org.au>
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>>%p requires a `void *' arg.
>What's the official policy here? I used a cast of (intptr_t) in the
>changes I submitted, but if we should be using %p and (void *) instead,
>so be it.
Casts (to_intptr_t) require a `void *' operand (at least if you want
intptr_t to be guaranteed to not lose information and don't want
to see the raw bits in the pointer). Also, the width of intptr_t is
machine-dependent. This makes printing pointers by casting to (intptr_t)
even more onerous than printing them by casting to (void *), e.g.:
struct foo *bar;
printf("%?\n", (intptr_t)(void *)bar);
where '?' is a machine-dependent format suitable for intptr_t's.
%p should be used for pointers except possibly where you want complete
control of the format or want to see the raw bits in the pointer.
Anything that requires a cast should be avoided since casts defeat type
checking and may cause undetected overflow. Unfortunately, %p usually
requires a cast.
Bruce
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