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From: Terry Lambert <tlambert@primenet.com>
Message-Id: <199711040230.TAA14861@usr09.primenet.com>
Subject: Re: gcc and bitfields
To: jwm@CSUA.Berkeley.EDU (John Milford)
Date: Tue, 4 Nov 1997 02:30:23 +0000 (GMT)
Cc: kuku@gilberto.physik.rwth-aachen.de, freebsd-hackers@freefall.freebsd.org
In-Reply-To: <199711021618.IAA02063@soda.CSUA.Berkeley.EDU> from "John Milford" at Nov 2, 97 08:18:29 am
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> By default gcc pads structures to make make the size a multiple of 4 bytes.
> Try:
> 
>    struct C_OPEN {
>         int a;
> 	int b;
> 	unsigned xdt:1;
> 	unsigned reserved:15;
>    } __attribute__ ((packed));


Or you can keep the code portable to DOS by not using the bogus
GNUish namespace intrusion "__attribute__":

#pragma pack(1)
    struct C_OPEN {
         int a;
 	int b;
 	unsigned xdt:1;
 	unsigned reserved:15;
    };
#pragma pack(4)
/*
 * GCC will take "pack()" (no arguments) to reset; I don't remember
 * if MSVC++ can, however... you should check, and use the no argument
 * version, if possible.
 */


Also:
	cd /sys/i386/include
	grep pragma *.h

...there's already precedent favoring "#pragma pack(<N>)" over
"__attribute__" in FreeBSD.

					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.