Allocation on stack versus from heap. Re: of course!

[Peter da Silva]

In article <17377 at rpp386.cactus.org> jfh at rpp386.cactus.org (John F. Haugh II) writes:
> In article <7132 at ficc.uu.net> peter at ficc.uu.net (Peter da Silva) writes:
> >I take it you have never worked on a machine with a fixed-size stack.

> and you've never seen a heap/stack collision.

Yes, I've worked on a PDP-11. This is what usually happens:
	Heap gets close to stack.
	IF a large heap request comes first
	THEN it fails, malloc returns 0, and you can fall back.
	ELSE a large stack request comes first
	THEN you die.

Moral: make large requests on the heap, where you can control what
happens when they fail.

> >And if your stack size is variable, then your big allocation can still
> >increase your stack segment, and it's still never going to decrease. So you
> >still lose there.

> it also doesn't take care to properly align the return pointers and
> a few other nasties.

What doesn't? The hack I threw together for allot/forget? Sure. It's a
brain-dead hack. I *said* it was a hack. That's an implementation detail.

This isn't nuclear engineering, you know.
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`-_-' Peter da Silva <peter at ficc.uu.net> <peter at sugar.lonestar.org>.
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