Xref:	news2.mv.net comp.os.msdos.djgpp:5407
From:	Shawn Hargreaves <slh100 AT york DOT ac DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Using Structures in Assembly
Date:	Wed, 26 Jun 1996 09:48:39 +0100
Organization:	The University of York, UK
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Message-ID:	<Pine.SGI.3.91.960626092512.1959A-100000@tower.york.ac.uk>
NNTP-Posting-Host:	tower.york.ac.uk
Mime-Version:	1.0
In-Reply-To:	<31D00541.3729@tiac.net>
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On Tue, 25 Jun 1996, Nick Collier wrote:

> I am trying to convert some TASM code to AT+T syntax for use with djgpp. 
> How can I use a structure that gets used by a function coded in 
> assembly. Do need to use the offsets from the beginning of the structure 
> or can I use .globl in someway to do this. Or are both these completely 
> wrong. Please help.

I ran into this problem with Allegro, and came up with a solution which, 
although not particularly elegant, seems to work ok.

I wrote a little C program which #includes all my header files, so it can 
see the definitions of all my structures, and then writes a load of 
offsets as #defines into a text file (eg. fprintf("#define MEMBER_NAME 
%d\n", offsetof(structure, member)). If you compile your asm code with a 
capital .S, so it gets run through the C preprocessor, you can #include 
this file in the asm code and use these constants, eg. movl ptr, %esi ; 
cmpl $0, MEMBER(%esi).

It's not very clean or simple, but you can set make up to rebuild the 
offset header whenever your C headers change, and it makes it relatively 
easy to share structures between C and asm without having two sets of 
definitions that can get out of sync with each other...


/*
 *	Shawn Hargreaves.        Why is 'phonetic' spelt with a ph?
 *	Check out Allegro and FED on http://www.york.ac.uk/~slh100/
 */

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