Re: checking against signed integer overflow

[Paul Eggert]

On 12/6/20 4:05 AM, Bruno Haible wrote:
> Hi Paul,
>
> > I installed the attached patch to do that
>
> Very nice! I made a tweak to the first example, to use printf() instead of
> print(). Hope you agree.
>
> > Your reaction to the *_WRAPV names just goes to show how bad I am with 
> > marketing....
>
> This set of macros would be worth publicizing, e.g. through an announcement
> on planet.gnu.org. If you agree, we would
>    1) publish the current gnulib doc on www.gnu.org (as we do occasionally
>       anyway) [I can do that],
>    2) write a news entry in https://savannah.gnu.org/projects/gnulib
>    3) approve it, also through https://savannah.gnu.org/projects/gnulib

Sure, here's a quick draft at a news entry.

Gnulib's intprops module has new macros INT_ADD_OK, INT_SUBTRACT_OK, and 
INT_MULTIPLY_OK that support portable overflow checking while doing integer 
arithmetic. On GNU platforms the macros typically use only a single machine 
instruction more than ordinary integer arithmetic would.