Re: Where are returned values stored?

["Nick Roberts" <nick.roberts@acm.org>]

"Robert I. Eachus" <rieachus@comcast.net> wrote in message
news:fP2dnc8B4Y6kNyPdRVn-hA@comcast.com...

> Warren W. Gay VE3WWG wrote:
> > ...
> > Yes, of course.  You must still however, carve up the
> > address space for the stacks, whether the vm pages are
> > allocated or not.
>
> Actually, no.  There is one of those obvious in hindsight neat
> tricks. Don't allocate the address space for the stack and leave
> the pointer to the stack null/invalid.  When the stack needs to
> be used, both the address space and physical space have to be
> allocated and can then be used.  This helps a lot in Ada, where
> most tasks will never need or use the return stack.

Um, I think this is one of those comments that needs to be taken with a
pinch of salt :-)

Are you (Robert) talking about the main (control, primary) stack? I suspect
most (in fact, all) tasks will use this, even if not much. The IA-32
actually demands the existence of a valid stack (SS:ESP must be valid)
before it will execute anything. I suppose this trick could be used with a
secondary stack. I suppose it could apply to tasks prior to the start of
their execution.

However, it doesn't really detract form the point that, when the stacks
/are/ used, they must be allocated somewhere in your address space.

-- 
Nick Roberts