Re: round() on arm vs aarch64

On Tue, Nov 15, 2022 at 9:58 AM Stephanos Ioannidis <[email protected]>
wrote:

> On Tue, 2022-11-15 at 09:38 -0600, Joel Sherrill wrote:
> > Digging a bit, I noticed a huge block of <cmath> is ifdef'ed out for
> > aarch64.
> > I found the file c++config.h which is different between the two.
> >
> > Based on the diff of the arm and aarch64 versions, arm has
> >  _GLIBCXX_USE_C99_MATH_TR1 defined but aarch64 does not.
> >
> > I have no idea where the settings in this file come from but this
> > appears to be the key difference.
> >
> > More insight appreciated.
>
> Funny how I came across a similar issue today. The following link might
> be of help in understanding what is going on:
>
>
> https://github.com/zephyrproject-rtos/sdk-ng/issues/566#issuecomment-1315165640


Thanks for the quick reply. It is a shame that the lack of long double
methods
prevents the entire TR1 from being there. Wouldn't it be ok to just have the
prototypes and let the user get a link error?

Anyway, I have been very very slowly picking at newlib long double support
but haven't gotten a complete patch set that is acceptable. See
https://sourceware.org/newlib/ for the discussion. I am happy to share
my work in process.

As I recall, one of the sticking points is that the FreeBSD code has
long double support for architectures which have true long double but
nothing as far as I can tell for architectures where double == long double.
I was proposing a configure time selection of the current code for when
long double == double and use the imported FreeBSD code when there
is true long double support.

Making libstdc++'s configure probe more forgiving would be a nice step
but long term having complete long double support would be better.

How to progress?

--joel


>
> Regards,
>
> Stephanos
>