Re: [PATCH 6/7] stdio-common: Keep trailing zeros where %#g rounds into a new decade

On Fri, Aug 28, 2026 at 7:50 AM Adhemerval Zanella Netto
<[email protected]> wrote:
>
>
>
> On 24/08/26 19:16, Matt Turner wrote:
> > The g and G conversions choose between the f and e styles according to
> > the exponent the value has once rounded to the requested number of
> > significant digits.  Where the value is small enough for the f style but
> > rounding then carries into a new decade, printf_fp rewrites the digits
> > it has already produced into the e style, recomputing along the way how
> > many fractional digits the leading digit now leaves room for.
> >
> > FRACDIG_MIN, which the alternative form sets to the number of fractional
> > digits that have to be retained rather than stripped, was left behind at
> > the value computed for the f style.  Where the value filled the whole
> > integer part that is zero, so all the fractional digits were then
> > stripped from a result the '#' flag requires to keep them:
> >
> >   printf ("%#.2g", 99.9)    gave "1.e+02" rather than "1.0e+02"
> >   printf ("%#g", 999999.9)  gave "1.e+06" rather than "1.00000e+06"
> >
> > Update FRACDIG_MIN along with FRACDIG_MAX.  Without the alternative form
> > nothing retains trailing zeros, so the outcome is unchanged there.
> >
> > None of the values the conversion tests iterate over round this way, so
> > add one that does at a precision they cover.
> >
> > Tested on x86_64-linux-gnu.
>
> LGTM, thanks. I think this can be installed independently of the set and
> I think we should open a bug report to track it.
>
> Reviewed-by: Adhemerval Zanella  <[email protected]>

Thanks, feel free to peel off patches from this series and merge them
independently.

I've filed a bug
(https://sourceware.org/bugzilla/show_bug.cgi?id=34578) for this
issue.