Re: Planning for glibc releases --- What should go into glibc 2.40?

[Joseph Myers <josmyers@redhat.com>]

On Wed, 14 Feb 2024, Paul Zimmermann wrote:

>        Hi Carlos,
> 
> > https://sourceware.org/glibc/wiki/Release/2.40#Planning
> >
> > Please add items to the plan :-)
> 
> I don't think I have write access to the wiki, but I'd like to see the 
> new C23 math functions (acospi, asinpi, atanpi, atan2pi, cospi, sinpi, 
> tanpi, exp10m1, exp2m1, log10p1, log2p1, rsqrt) available in GNU libc.

I think this wiki list is for things that already have patches - not for 
aspirations that some feature would be nice to have.

I hope to work on these functions at some point, but it depends on time 
available between other projects (and my time available will be very 
limited from April through July in general).  As previously discussed, the 
functions would start with type-generic templates where possible (thereby 
making the functionality available for all formats, including legacy ones 
such as IBM long double, without needing individual implementations for 
each format - we don't want functions for only a subset of formats - and 
dealing with all the documentation, test inputs, ABI baseline etc. updates 
at that point), and then faster and more accurate implementations can be 
incrementally added for particular (function, format) pairs later (with 
benchmarks added for any function being replaced to show that the new 
implementation is indeed faster).

Note that your list omits the logp1 alias, and the compoundn rootn pown 
powr functions.  Also, there are functions we have from TS 18661-1 whose 
prototypes changed in C23: we need to change the prototypes of fromfp 
functions (see bug 28327), with backwards ABI compatibility similar to 
that for totalorder.

On the C23 front, there is at least one feature where a patch has already 
been posted but needs review and updating (to put things in the latest 
NEWS section, at least): the new optional time bases (posted by Yonggang 
Luo last June).  There are also several C23 features where we don't yet 
have patches, but that would be simpler to add than the new libm 
functions.

-- 
Joseph S. Myers
josmyers@redhat.com