Date: Tue, 14 Nov 1995 08:27:52 +1100 From: Bruce Evans <bde@zeta.org.au> To: davidg@Root.COM, peter@jhome.dialix.com Cc: ache@astral.msk.su, committers@freebsd.org, security@freebsd.org Subject: Re: cvs commit: CVSROOT log_accum.pl Message-ID: <199511132127.IAA07800@godzilla.zeta.org.au>
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>BTW: I suspect "struct ucred" should be reordered for better internal
>alignment..
>It is currently:
>struct ucred {
> short cr_ref;
> long cr_uid;
> short cr_ngroups;
> long cr_groups[NGROUPS];
>}
Actually, it is currently:
struct ucred {
u_short cr_ref;
^^
uid_t cr_uid;
^^^^^
short cr_ngroups;
gid_t cr_groups[NGROUPS];
^^^^^
}
uid_t and gid_t just happen to be unsigned long. This is bogus. They
are u_int32_t in NetBSD. I think they should be machine dependent and
normally u_int if u_int has more than 32 bits, otherwise u_long.
>The order of cr_ngroups and cr_uid could be swapped making the whole
>thing 4 bytes smaller (assuming that I understand structure packing.. :-)
You can't tell the best packing in general. Putting the explicit char,
short, int and long types at the beginning of the struct is probably
best in general and works well here.
Bruce
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