From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Fri, 22 Oct 2004 11:20:42 -0600
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?
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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