Re: integer overflow handling for most-negative-fixnum

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

On 07/23/2018 12:57 PM, Stefan Monnier wrote:
> Another option for the "bitwidth case" is to do it outside of `format`.
> I.e. instead of
>
>      (format "%/32x" n)
>
> you'd use
>
>      (format "%x" (truncate-to-bitwidth n 32))
>
> where `truncate-to-bitwidth` would turn a negative number into its
> positive equivalent (mod 2^bitwidth).  That shouldn't be too hard to
> implement in Elisp once we have bignums.

Yes, with bignums it can be implemented this way, if I understand you 
aright:

(defun truncate-to-bitwidth (num bits)
   (logand num (- (lsh 1 bits) 1)))