[PATCH] Introduce --enable-math-noprivate

[Florian Weimer]

* Wilco Dijkstra:

> My question is, would a new config option really be useful? Errno can
> be set outside the critical paths, so inlining it doesn't help at
> all. Therefore this should be done by default.

I can submit a patch to that effect, basically making that part
unconditional.

> Similarly the strtod_nan* dependency seems worthwhile to remove too.

I haven't thought about this.  It's certainly a bit of a code
duplication.

Joseph, any thoughts on that?

> If these are the main dependencies between libc and libm, I can't see
> the value of adding a new config option.

The IFUNC resolvers on x86-64 use a GLIBC_PRIVATE symbol from ld.so.
That's going to be a bit more complicated to remove, and what we have to
do there is still a bit unclear to me.  (I had a proof-of-concept patch
which actually reimplemented part of sysdeps/x86/cpu-features.c, but
didn't want to submit that so far.)

My expectation is that at least for x86, we'd still want
--enable-math-noprivate.  (Maybe not in the distant future when we can
assume that H.J.'s new feature bit access interface is available
everywhere. 8-)

Thanks,
Florian