/bin/sh arithmetics: BIG NUMBERS

[Mike Barcroft]

Alex Semenyaka <alexs at ratmir.ru> writes:
> Collegues,
> 
> I need your opinion. Several days ago I've send to -hackers mailing list a
> patch for /bin/sh which introduce 64-bit arithmetic operations instead of
> 32-bit ones we have now. There were now principal objections there but
> Giorgos Keramidas <keramida at freebsd.org> adviced me to ask here about the
> FreeBSD's standards compliance of this. I hope that it IS ok withem but
> I want to be absolutely sure.
> 
> Argumentation "pro":
> 
> 1) POSIX and SUSv3 _require_ at least long type for integers in the shell, and
>    explicitly _allow_ to use integer in the range beyond the long type range.
>    SUSv2 _requires_ long and _allows_ extensions as well (but there are no
>    explicit words about wider range as in SUSv3). It is the theoretical aspect.
> 2) ksh, zsh and bash handle longer integers properly. The last two have
>    64-bit arithmetics and first one has float inside. That is the compatibility
>    aspect.
> 3) These days we have a lot of 64-bit stuff in the system: from ipfw counters
>    to file sizes. Moreover we really have such big numbers in everyday FreeBSD
>    usage. But now /bin/sh silently produce just wrong results dealing with
>    such numbers due to overflow. So old scripts which worked from 1997 or such
>    now can produce meaningless results and it will not be even noticed.
>    I can suggest to write new ones with bash or zsh but some people continue
>    to use their old stuff (don't touch while works, you know). So it IS better
>    to change our basic shell and extend it's abilities. That is the practical
>    aspect.

Sounds like its standards conformant.

> Any "contras"?

I would suspect there's a performance penalty on i386.  Have you done
any benchmarking?

Best regards,
Mike Barcroft