Re: Using qsort(3) in the kernel

[Johnny Billquist <bqt%softjar.se@localhost>]

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.

        Johnny