Date: Mon, 13 Dec 2004 00:26:01 -0500 From: Ken Smith <kensmith@cse.Buffalo.EDU> To: Ken Smith <kensmith@cse.Buffalo.EDU> Cc: Wilko Bulte <wb@freebie.xs4all.nl> Subject: Re: cvs commit: src/sbin/ifconfig ifconfig.c src/sys/net if.c if.h Message-ID: <20041213052601.GB12611@electra.cse.Buffalo.EDU> In-Reply-To: <20041212215540.GD5960@electra.cse.Buffalo.EDU> References: <200412122012.iBCKCou6068020@repoman.freebsd.org> <20041212204111.GB5503@electra.cse.Buffalo.EDU> <20041212205321.GA28802@odin.ac.hmc.edu> <20041212212850.GA1493@freebie.xs4all.nl> <20041212215540.GD5960@electra.cse.Buffalo.EDU>
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On Sun, Dec 12, 2004 at 04:55:40PM -0500, Ken Smith wrote:
> I didn't check as thoroughly as Brooks said he did but I whipped up
> a very crude little test and ran it on beast:
>
> #include <sys/param.h>
> #include <sys/socket.h>
> #include "if.h"
>
> main()
> {
> struct if_data foo;
> u_char *addr1, *addr2;
>
> printf("sizeof if_data %d\n", sizeof(foo));
> addr1 = (u_char *)&foo;
> addr2 = (u_char *)&foo.ifi_mtu;
> printf("offset ifi_mtu %d\n", (int)(addr2 - addr1));
> }
>
As a community service... Don't write code like that... :-)
I was having a little trouble finding the right combination of headers
to get offsetof() working. This should be better:
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <sys/param.h>
#include <sys/socket.h>
#include "if.h"
main()
{
struct if_data foo;
size_t distance;
printf("sizeof if_data %d\n", sizeof(foo));
distance = offsetof(struct if_data, ifi_mtu);
printf("offset ifi_mtu %lu\n", (unsigned long)distance);
}
--
Ken Smith
- From there to here, from here to | kensmith@cse.buffalo.edu
there, funny things are everywhere. |
- Theodore Geisel |
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