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From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199609281556.KAA01300@dyson.iquest.net>
Subject: Re: stack
To: guido@gvr.win.tue.nl (Guido van Rooij)
Date: Sat, 28 Sep 1996 10:56:43 -0500 (EST)
Cc: dyson@FreeBSD.org, FreeBSD-hackers@FreeBSD.org
In-Reply-To: <199609281552.RAA05940@gvr.win.tue.nl> from "Guido van Rooij" at Sep 28, 96 05:52:49 pm
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> John S. Dyson wrote:
> > > When I allocate something on the stack, isn't it supposed to be completely
> > > zero?
> > > like:
> > > main(int argc, char **argv) {
> > > 	char buf[1000];
> > > 
> > > ...
> > > }
> > > 
> > > Then buf should be zero, or am I missing something here?
> > > 
> > The first time that you use a page the kernel will demand zero it.  But
> > if you have used the stack space before, it will be whatever you left in
> > it.
> 
> I used exactly this program:
> main() {
> 	char buf[1000];
> 
> 	write(1, buf, 1000);
> }
> 
> The resulting file did not conatin only zero's. I think this is weird.
> This is on a 2.1.5R system
> 
If something had been called before main(), by the startup code, then there
will likely be stuff left on the stack.

John