bug#8611: fixnum arithmetic should not wrap around

[Paul Eggert <eggert@cs.ucla.edu>]

On 05/04/11 05:57, Stefan Monnier wrote:
> Conversion to float is in general not a good idea

OK, how about using bignum instead?  That would be quite a bit of
work, and I wouldn't want to embark on it if the answer is going
to be "don't fix something that isn't broken".  Clearly the
current behavior is broken at some level, since we have mathematical
nonsense like adding two positive numbers gives you a negative number,
and this results in much real Emacs Lisp code going into contortions;
but if the overall idea is that this is good enough, then I should
not bother.

Perhaps I should raise this on the emacs-devel list?  It seems to be
a more general point, one that surely has come up before.