Path: chuka.playstation.co.uk!news
From: Nick Slaven <NickSlaven@compuserve.com>
Newsgroups: scee.yaroze.programming.codewarrior
Subject: Re: Debugger problem
Date: Sun, 07 Jun 1998 19:56:31 +0100
Organization: PlayStation Net Yaroze (SCEE)
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Mark Wilson wrote:
> 
> Another bug-ette has just reared its head, unless I've done something really
> stupid... which has been known.
> 
> A routine I was working on was playing up, so I stuck in a breakpoint. There
> my troubles began.
> 
> void GetCurrentPosition(Obj *obj)
> {
> 
>  short i, d, deltax, deltay;
> 
>  int dinc1, dinc2, xinc1, xinc2, yinc1, yinc2;
> 
>  deltax = obj->tx - obj->sx;
>  deltay = obj->ty - obj->sy;
> 
> Setting a breakpoint on the "deltay = " line I noticed that deltax was
> coming out as 0, not -640. Stepping through the next line, I found that
> deltay was being calculated OK.
> 
> So I stuck in a printf before the calculation like
> 
> printf("%d\t%d%t%d\n", obj->tx, obj->sx, obj-tx - obj->sx);
> 
> which returned exactly the figures I'd expected, 0, 640 and -640. A printf
> AFTER the calculation showed that deltax was in fact being set up correctly,
> and was just not being displayed in the debugger.
> 
> Any ideas?
> 
> Mark

I think this is a bug in the debugger, 'cos I've also had the same
problem. I think that if the compiler optimises your local 
variables into registers then the debugger wont display them. If you open up the
register window you will find that one of the registers 
will update with the values you'd expect. 
This can be overcome by using the keyword "volatile" as follows

volatile short i,d,deltax,deltay;

and the debugger will display the variables correctly.

cheers

Nick Slaven

-- 

http://www.netyaroze-europe.com/~nslaven/