Re: [PATCH v2] stdlib/strfrom: Change -NAN test to multiple possible results (bug 29501)

[Joseph Myers <joseph@codesourcery.com>]

On Mon, 19 Sep 2022, Florian Weimer via Libc-alpha wrote:

> * Joseph Myers:
> 
> > On Sun, 18 Sep 2022, Florian Weimer wrote:
> >
> >> I think the conversion to double is required because according to the
> >> quote from ISO/IEC TS 18661-1:2014 in the bug, strfromf is defined in
> >> terms of snprintf, and calling snprintf promotes float arguments that do
> >> not correspond to a declared parameter to double as part of the default
> >> argument promotions.
> >
> > I don't think reading as literally passed to the variable-arguments 
> > function snprintf is very helpful, considering that the strfrom functions 
> > are supported for types that have no corresponding printf format (and 
> > supporting e.g. strfromf128 is one motivation for having these functions).  
> > That is, the equivalence to snprintf should be considered to be for the 
> > semantics of conversion to character strings, rather than for applying 
> > default argument promotions.
> 
> Ah, so a bug in TS.  Can the text still be fixed, or is this impossible
> because it's a TS?

I've noted it as something to consider submitting as an NB comment on the 
C2x CD ballot.  TS 18661-1, -2 and -3 will be superseded by C2x (and thus 
hopefully withdrawn at their next systematic review after C2x).  There 
should be subsequent revisions of -4 (the parts not merged into C2x, plus 
new functions from IEEE 754-2019) and -5, updated to apply to C2x.

-- 
Joseph S. Myers
joseph@codesourcery.com