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Mail Archives: djgpp-workers/2003/02/12/17:30:11

From: sandmann AT clio DOT rice DOT edu (Charles Sandmann)
Message-Id: <10302122051.AA01639@clio.rice.edu>
Subject: Re: Checking for stack overflow
To: djgpp-workers AT delorie DOT com
Date: Wed, 12 Feb 2003 14:51:50 -0600 (CST)
In-Reply-To: <Pine.OSF.4.51.0302121051330.32166@sirppi.helsinki.fi> from "Esa A E Peuha" at Feb 12, 2003 11:12:49 AM
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> I committed patch for __djgpp_stack_top; we should have it anyway
> because __djgpp_stack_limit + _stklen won't be the real top of stack if
> it's not aligned to 8-byte boundary.

Fine.  It would be nice if this was documented, but I don't see any
docs for __djgpp_stack_limit either (sigh).

> > I think the change to "jb" fixes the signed-ness issue - so I'm not
> > sure this is really needed.
> 
> I don't understand.  Do you mean that a single unsigned comparsion
> against __djgpp_stack_limit is enough?  It's not; it's even worse than
> the single signed comparsion (if esp ever wraps below zero, the unsigned
> comparsion will never detect it, while the signed one will usually do).

I think you're right - too much typing without thinking on my part

> > I'd be interested to see this working, see how much of a run-time
> > impact it has, and how much checking the second limit changes the
> > run-time performance.
> 
> I'll provide two version of patched gcc, one with one signed comparsion
> and the other with two unsigned ones.

I think a single version with the right behavior would be best :-)

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