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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To: djgpp AT delorie DOT com
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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/
 */