> Recursive routines (ones that call themselves) obviously must be
> re-entrant, but re-entrant routines do not need to be used recursively.

> The compiler I use for the
> 68HC11 (Whitesmiths) has recursive routines and they are a must for me.

> I am in the middle of a math computation (e.g. divide), and an interrupt
> occurs where the ISR needs to perform the same kind of math computation,
> the math routine better be re-entrant.  But just because those two
routines
> are using the math function at the same time does not mean a large amount
> of stack space is used.

The PIC (except the high-end ones?) do not have a data stack, so even
the re-entrancy which you mention is difficult to achive. I know, I have
written my own PIC compiler. The best (compact) PIC code uses fixed
addresses for data, allocated pseudo-stack wise. This makes re-entracy
impossible. I think the best a compiler could do is generate separate
code for everything which is used during an interrupt. Lucky that PICs do
not have nested interrupts....

wouter.