Pip Cet wrote:

> I think we can be clever and wrap calls to mpz_mul_2exp (which can
> create arbitrary bignums) and whatever Fexpt uses....  I'd suggest a much
> lower limit until/unless the C-g issue is fixed, perhaps overridable
> by a user preference if people really want to use big bignums.

Yes, this sounds good. After stressing Emacs with bignums for a bit, I found 
that it was too easy to get Emacs to abort or hang by creating large bignums.

> I'm not sure what a reasonable limit would be, but I think a global
> limit of bignum size to something that allows for "immediate"
> computations would be best.

I installed the attached patch to do that. It tentatively defaults to a limit of 
2↑↑5 (i.e., 2**65536) for bignums, overrideable by setting a new variable 
'integer-width' that defaults to 65536. This default should be big enough for 
almost all Emacs applications and should avoid issues of aborts and hangs.