From: "Ronald G. Minnich" <rminnich@lanl.gov>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] am I nuts? does 8c support packed structs?
Date: Fri, 22 Oct 2004 11:20:42 -0600 [thread overview]
Message-ID: <Pine.LNX.4.58.0410221109560.15945@linux.site> (raw)
In-Reply-To: <5ae212d006c8c514c89c49f0258ebd36@vitanuova.com>
On Fri, 22 Oct 2004, C H Forsyth wrote:
> hj were only dicks on the mips it seems, but it's easy to add it to 8c.
>
Here's a test of dicks on 8c today:
#include <u.h>
#include <libc.h>
#pragma hjdicks on
struct a {unsigned long x; char c; };
#pragma hjdicks off
struct a a;
main(){
print("size %d\n", sizeof(a));
}
This yields 8, with dicks on or off.
In gcc, for this:
struct a {unsigned long x; char c; } __attribute__ ((packed));
struct a *a = 0;
main(){
printf("size %d, addr %p\n", sizeof(*a), &a->c);
}
you get a size of 5.
"How do you create TCP headers without packed structs?" is one question I
got. I guess Plan 9 is quite possibly the "here's how" except of course
everyone did this before packed structs (or even gcc, or even before C
compilers that aligned structs and struct members for that matter -- was
there a C compiler before gcc? one wonders. The mind boggles).
Unless there's another 8c pragma I have not heard of, I'll stuck to
marshalling data by hand.
ron
next prev parent reply other threads:[~2004-10-22 17:20 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-22 15:26 Ronald G. Minnich
2004-10-22 15:30 ` Russ Cox
2004-10-22 15:49 ` C H Forsyth
2004-10-22 16:37 ` Ronald G. Minnich
2004-10-22 16:54 ` C H Forsyth
2004-10-22 21:13 ` Bruce Ellis
2004-10-22 21:00 ` Charles Forsyth
2004-10-22 16:51 ` Russ Cox
2004-10-22 17:27 ` Ronald G. Minnich
2004-10-22 17:20 ` Ronald G. Minnich [this message]
2004-10-22 17:28 ` Russ Cox
2004-10-22 17:30 ` Ronald G. Minnich
2004-10-22 17:29 ` jmk
2004-10-22 17:31 ` Ronald G. Minnich
2004-10-22 17:50 ` Brantley Coile
2004-10-22 18:32 ` C H Forsyth
2004-10-22 18:14 ` Charles Forsyth
2004-10-22 19:25 ` boyd, rounin
2004-10-22 19:35 ` Ronald G. Minnich
2004-10-22 19:38 ` boyd, rounin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.58.0410221109560.15945@linux.site \
--to=rminnich@lanl.gov \
--cc=9fans@cse.psu.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).