Re: [RFC PATCH] explicitly mark recursion count

[Jörn Engel]

On Wed, 2 June 2004 07:15:07 -0700, Linus Torvalds wrote:
> On Wed, 2 Jun 2004, Jörn Engel wrote:
> > 
> > For a->b->c->a type recursions, I also need to identify all involved
> > functions in the correct order, that's where my ugly format comes
> > from.
> 
> Why?
> 
> You really only need to know that _one_ of the entries break the 
> recursion, and you need to know what the break depth is for that one 
> entry.
> 
> So for example, if "c" is annotated with "max recursion: 5", then you know 
> that the above loop will recurse at most 5 times.
> 
> I don't see why you need any other information.

Then you see something I don't see.  For example there are quite a few
recursions with some function like

void foo(int depth)
{
	if (!depth) {
		bar(1);
	}
	...
}

bar will, maybe through several more functions call foo(1).

How can you say that foo will beak this recursion after two rounds
max?  What if a changed bar decrements the depth value?  The recursion
will run for infinity now, won't it?  And whoever changed bar doesn't
have a clue that he now fucked up your comment to foo.

I claim:
There is no way to tell the depth of any recursion without looking at
all involved functions.

Prove me wrong, please.

Jörn

-- 
When in doubt, use brute force.
-- Ken Thompson
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