From:	"John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Padding Question
Date:	Fri, 06 Dec 1996 20:24:12 -0800
Organization:	Three pounds of chaos and a pinch of salt
Lines:	42
Message-ID:	<32A8F16C.596F@cs.com>
References:	<32A810D9 DOT 366E9B4E AT m-net DOT arbornet DOT org> <32A85B15 DOT 4015 AT skygames DOT com>
Reply-To:	fighteer AT cs DOT com
NNTP-Posting-Host:	ppp222.cs.com
Mime-Version:	1.0
To:	Kevin Baca <kbaca AT skygames DOT com>
CC:	Rohit Jalan <rohitj AT m-net DOT arbornet DOT org>
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Kevin Baca wrote:
> 
> Rohit Jalan wrote:
> >
> > Is it possible to stop gcc from padding structures ?
> >
> 
> #pragma pack(1)  /* use one byte as minimum packing size */

#pragma is an evil, hackish way to make gcc pack structures.  The DJGPP
Frequently Asked Questions list (v2/faq202b.zip), chapter 22.9, tells
you exactly how to go about packing structs in DJGPP, and refers you to
the gcc reference which details the syntax of the __attribute__()
extension.

The following will cause gcc to pack the indicated structure to use the
minimum possible amount of storage space:

struct foo
{
    int		zork[3];
    char 	name[33];
    short	stuff;
    long double total;
} __attribute__((packed));

Note that there was a bug in the gcc compiler distributed with DJGPP
v2.00 that caused struct packing to fail under C++, and it was this bug
that prompted the use of #pragma pack(1) ... #pragma pack().  If you are
writing C++ code in v2.00, you can use this method to make gcc pack
correctly, but it is far better to upgrade to v2.01, which contains a
fixed version of gcc in v2gnu/gcc2721b.zip.  See the FAQ section 22.10
for more information.

Good luck!

-- 
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| John M. Aldrich, aka Fighteer I |        fighteer AT cs DOT com          |
| Proud owner of what might one   |   http://www.cs.com/fighteer    |
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