Re: Proper Tail Recursive C++

wdijkstr@armltd.co.uk wrote:
> In order to be able to generate a tail-recursive call to f, a C/C++
> compiler needs to know the following:
>
> A It is OK to access data *below* the current stack frame. In other
> words, the stack is not used by interrupts, exception handlers, etc.
>
> B The function which is called, nor its decendants do use the stack in
> a way which may overwrite the live parts of the array. Or, simply,
> the function which is called must be a simple leaf function (doesn't
> use stack).
>
> For many runtime systems A can never hold, and B is simple too hard to
> check at compile time (except for the case that g was before f in the
> source).


On some run-time systems it may be possible to 'redefine' the topmost
stack frame to be bigger on each 'tail-call'. Thus, you may be able
to achieve 'tail-calling' even though the tail call allocates live
storage. I would imagine that such a system would require both a
'stack' and a 'frame' pointer to work correctly.


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