Re: [musl] [PATCH] vfprintf: support C2x %b and %B conversion specifiers

["Jₑₙₛ Gustedt" <jens.gustedt@inria.fr>]

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Rich,

on Mon, 12 Sep 2022 09:59:04 -0400 you (Rich Felker <dalias@libc.org>)
wrote:

> I don't see anything else immediately wrong. No rush to submit an
> updated patch. Let's first figure out the timeline for C2x features,
> and I'll try to figure out what's going on with the weird buf[] size
> expression and clean it up separately so that your patch is just
> adding the feature and not also fighting with historical cruft.

The specification of C23 has been finished in July, what follows now
in WG14 is merely editorial on the standard text itself and should not
have much impact on how things should be implemented. The current
draft is here

      https://open-std.org/jtc1/sc22/wg14/www/docs/n3047.pdf

and any changes from there should not have impact on implementations,
unless a majority of the national bodies imposes withdrawal of
specific new features. The timeline is publication in end of 2023, so
this leaves basically one year to have things ready when the new
standard is published

Already for `printf` and friends there are several additions, not only
the `b` formats but, e.g, also formats for the fixed-width types and
for the new bit-precise types.

Otherwise, there are changes to the C library all over the place, but
in general these are small and should be doable with limited work
load, in particular for implementations that also implement
POSIX. Those headers that have changes also are now supposed to have a
feature macro that describes the version for which a header works,
such that support for C23 can be added stepwise to C library
implementations.

There is one big addition, though, for the decimal floating point
types, but support here is optional. I don't know if there is already
an open stand-alone implementation of that stuff, but I think that
that should be the goal, instead of repeating the effort for every C
library implementation that is out there.

Jₑₙₛ

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