bug#47085: du: why does 'usage' show prefixes 'Z' or 'Y' if they are disallowed?

[Glenn Golden]

Paul Eggert <eggert@cs.ucla.edu> [2021-03-12 11:46:52 -0800]:
> On 3/11/21 8:53 PM, L A Walsh wrote:
> > Why are those suffixes listed as valid under the program 'usage'
> > and manpage, when they are automatically disallowed?
> 
> They are valid if your computer has wide-enough integers. As far as I know
> no platform supports Y and only one or two supports Z, but the documentation
> is future-proofing.
> 
> Conversely, if you're running on a really small computer that doesn't even
> support 64-bit integers, even 'T' is too wide.
> 
> I doubt whether it's worth complicating the manual for this minor detail, as
> the current diagnostic "'Y" too large" is accurate as far as it goes.
> 

The manual actually does address this briefly:

coreutils.info 8.32, Section 2.3:

   "Large sizes like ‘1Y’ may be rejected by your computer due to
    limitations of its arithmetic."