[fpc-pascal]Double-precision recursion

[Marco van de Voort]

> > Looks like a FPU stack overflow...?
> 
> You may be onto something here.
> 
> I didn't know there a separate stack in the FPU.  How can I learn more
> about how Free Pascal utilizes it?

Try to compile using -al, and check the generated assembler.
 
> > If you reduce the line "p := get+cof(n);" just to "p := cof(n);", then
> > the program works. (ehmm, it doesn't crash anymore...)
> 
> Yes, but in the "real" program from which this trivial example was
> derived, this is not an option.

The problem is that if you kill this behaviour, you loose a lot of speed.

One could try to detect simple recursion in the compiler, but this would
only detect a -> a -> a  recursion, and not a -> b -> a -> b -> a

> > But I'm somewhat surprised that BP sufferes from the same problem.
> 
> Apparently both BP and FP use the FPU stack (if there is one) the same
> way.  In this case, I'm surprised that the C version is not also subject
> to the same bug.

If BP behaves the same way, we are compatible, and then it is not a bug :-)