Re: [PATCH] Fix segmentation fault and infinite loop in jsonb_{plperl,plpython}

Hi Tom,

Thanks for taking a look.

> > The second bug affects only jsonb_plperl. It's possible to construct a
> > Perl object with circular references which will cause
> > SV_to_JsonbValue() to go into an infinite loop here:
>
> > while (SvROK(in))
> > in = SvRV(in);
>
> > I suggest fixing it by rewriting the while loop into a recursion with
> > check_stack_depth() call. This will make the behavior consistent with
> > jsonb_plpython.
>
> Unfortunately, your 0002 is too cute for its own good. I tried it
> here, with a not-especially-new gcc compiling at -O2, and found that
> the tail recursion in SV_deref() is optimized into a loop. So the
> stack doesn't grow and we still have an uninterruptible loop.

That's funny :)

> I don't immediately see a way to write that function so that the
> compiler is certain not to spot the tail recursion. Tricks like
> two mutually recursive functions might be seen through at
> sufficiently high -O levels.
>
> We could instead add a CHECK_FOR_INTERRUPTS, so that you can at
> least break out of the infinite loop. I'm not sure if the case
> is worth more effort than that.

Alternatively I could implement a check for the loops, if you feel
like this is worth the effort.

--
Best regards,
Aleksander Alekseev