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Re: Using qsort(3) in the kernel

On Nov 16, 2008, at 3:58 PM, Johnny Billquist wrote:

Anders Magnusson wrote:
Martin S. Weber wrote:
On Sun, Nov 16, 2008 at 01:41:34PM -0500, Steven M. Bellovin wrote:
The kernel stack is limited in size; if the recursion is too deep, it can exceed that limit. It's only safe to do recursion if you can (a)
guarantee the maximum depth; and (b) show that for all uses of this
routine, the total stack consumption will be low enough.
Doesn't gcc 4 in the meantime finally support that 70s technique of
tail call optimization? Thought I had read about that somewhen.. could
be mistaken tho.

Yes, gcc does, but that doesn't mean that it can use it for the qsort recursions.
Not all recursive calls can be optimized away.

Or put another way: not all recursions are tail recursions.

And not all architectures can do tail call optimizations...

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