Path: utzoo!telly!attcan!uunet!cs.utexas.edu!samsung!usc!ucla-cs!uci-ics!rfg
From: rfg@ics.uci.edu (Ron Guilmette)
Newsgroups: gnu.gcc
Subject: Re: packed structures in GCC 1.36?
Message-ID: <256A4870.18732@paris.ics.uci.edu>
Date: 22 Nov 89 07:19:11 GMT
References: <6632@columbia.edu>
Reply-To: Ron Guilmette <rfg@ics.uci.edu>
Distribution: gnu
Organization: University of California, Irvine - Dept of ICS
Lines: 32

In article <6632@columbia.edu> ji@close.cs.columbia.edu (John Ioannidis) writes:
>Hi!
>
>This topic has probably been discussed in the past, but I haven't been
>reading gnu.gcc lately. So, suppose I have the following structure:
>
>	struct _foo
>	{
>		char b1;
>		short w1;
>		short w2;
>		char b2;
>	};
>
>On my machine (a 386 machine running 386/ix (System V R3.2)), the size
>of _foo is eight bytes, with a "filler" byte between b1 and w1 and
>another after b2. This is fine, and there are good reasons for doing
>it. However, when I'm using that structure to access device registers...

Try this:

	struct _foo {
		unsigned b1:8;
		unsigned w1:16;
		unsigned w2:16;
		unsigned b2:8;
	};

Note that ANSI requires the fields to be unsigned, but GCC probably doesn't
care.

// rfg