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Date: Fri, 5 May 2023 01:16:01 +0200
From: Gabriel Ravier <gabravier@...il.com>
To: musl@...ts.openwall.com, enh <enh@...gle.com>,
Rich Felker <dalias@...c.org>
Cc: Jₑₙₛ Gustedt <jens.gustedt@...ia.fr>,
罗勇刚(Yonggang Luo) <luoyonggang@...il.com>,
Jason Ekstrand <jason@...kstrand.net>
Subject: Re: C23 implications for C libraries
On 5/4/23 18:07, enh wrote:
>
>
> On Thu, May 4, 2023 at 9:03 AM Rich Felker <dalias@...c.org> wrote:
>
> On Thu, May 04, 2023 at 08:19:42AM +0200, Jₑₙₛ Gustedt wrote:
> > Hi,
> >
> > on Wed, 3 May 2023 15:58:26 -0700 you (enh <enh@...gle.com>) wrote:
> >
> > > (i share others' skepticism that timespec_get() is very useful,
> >
> > I don't think that these interfaces by themselves are the most
> > interesting. The original motivation to create these interfaces stem
> > from the creation the integration of threads in to the C
> standard. And
> > there the monotonic and thread-specific clocks make all their sense.
> >
> > But also having process cpu usage in a well-defined interface
> (`clock`
> > usage is not portable for that) is a win.
> >
> > > and especially that non-ISO bases will ever be useful to
> anyway, but
> > > i like the idea of allowing future additions to "just work"
> with an
> > > old libc enough that i've implemented bionic's
> > > timespec_get()/timespec_getres() in this style.)
> >
> > Great!
> >
> > Do you have a link to that? The particular choices of values become
> > part of the ABI, sort-of. So it would be better to be consistent
> > between implementations.
> >
> > Would this motivate musl to accept patches for the optional
> bases that
> > come with C23? Or maybe the whole set?
>
> I'm a little bit hesitant/skeptical to do this in case the optional C
> ones eventually end up having requirements that conflict with the
> POSIX/extension ones or even just with our/Linux's implementation
> choices for them. This seems like locking ourselves into a commitment
> to support something that doesn't have a lot of motivation to exist.
>
>
> only having been involved with POSIX and not WG14, doesn't the latter
> take existing practice into account like the former does? (if they
> don't, it seems like anything they declare optional is then
> _inherently_ non-portable, and so something they'd be better off
> leaving out! *cough* annex k *cough*)
Clearly this isn't the case for at least some things they declare
optional, unless you think types like uint32_t or uintptr_t are useless.
In any case, I'm pretty sure they take existing practice into account -
for example, stuff like the %B specifier are technically optional given
that the uppercase conversion specifier namespace wasn't reserved, but
iirc there's no known implementation of C that uses it for any other
purpose.
>
> But I'm open to discussion.
>
> Rich
>
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