Re: C99 support in Newlib

["Andre Vieira (lists)" <Andre dot SimoesDiasVieira at arm dot com>]

On 14/01/16 15:27, Joel Sherrill wrote:
> On 1/14/2016 8:04 AM, Andre Vieira (lists) wrote:
> > On 11/01/16 14:27, Andre Vieira (lists) wrote:
> > > On 20/01/15 11:49, Freddie Chopin wrote:
> > > > On 01/20/2015 12:46 PM, Corinna Vinschen wrote:
> > > > > On Jan 20 12:21, Freddie Chopin wrote:
> > > > > > On 01/20/2015 11:06 AM, Corinna Vinschen wrote:
> > > > > > > On Jan 20 17:19, Joey Ye wrote:
> > > > > > > > Corinna, May I know which features are missing please?
> > > > > > > As far as I can tell, mainly the long double functions for targets
> > > > > > > with sizeof(double) != sizeof(long double).
> > > > > > I have one more - from my recent browsing of scanf() code, I assume
> > > > > > that
> > > > > > "%[...]" is supported, but "%[^...]" is not.
> > > > > No, it is.  See libc/stdio/sccl.c.
> > > >
> > > > Right, my mistake (; Sorry for the noise then (;
> > > >
> > > > Regards,
> > > > FCh
> > >
> > > Hi there,
> > >
> > > I thought I'd reply to this thread as it is very much related to my
> > > issue.
> > >
> > > In a recent GCC patch a change to an optimization, which now checks for
> > > the existence of libc support for C99 functions, lead to a regression
> > > for arm-none-eabi. This is because currently GCC is set up to assume no
> > > C99 support is available for arm-none-eabi. As far as I know this is
> > > because it comes with newlib and as this thread points out it does not
> > > claim to fully support C99. See
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69227
> > >
> > > Hopefully with some help I can figure out what GCC 'function classes'
> > > can be seen as supported by newlib for arm-none-eabi. These function
> > > classes are:
> > >
> > > function_c94:
> > >      functions only part of the standard in C94 or above.
> > > function_c99_misc:
> > >      functions only part of the standard in C99 or above.
> > > function_c99_math_complex:
> > >      math complex functions only part of the standard in C99 or above.
> > > function_c11_misc:
> > >      functions only part of the standard in C11 or above
> > >
> > > And there is also 'function_sincos' for which I couldn't find a
> > > definition though I assume its for the GNU extension 'sincos'.
> > >
> > > $arm-none-eabi-nm libm.a | grep sincos
> > > lib_a-w_sincos.o:
> > > 00000000 T sincos
> > > lib_a-wf_sincos.o:
> > > 00000000 T sincosf
> > >
> > >
> > > Can someone confirm the support or lack thereof for these classes in
> > > newlib for 'arm-none-eabi'.
> > >
> > > Thanks!
> > >
> > > BR,
> > > Andre
> >
> > As an investigation exercise I constructed a list of all functions in
> > the C99 standard and I checked whether the newlib version we build for
> > arm-none-eabi defined these and I found that it was missing quite a lot
> > of them! See attached file.
> >
> > That answers my question for the bugzilla ticket. We can not enable
> > function_c99_* function class support for arm-none-eabi.
>
> I think you checked it against C11. I spotted thrd_create on the list
> and don't think that is C99.
>
> My quick impression is:
>
> +  to agree that the math methods are C99 and missing.
> + thread, mutex and other concurrency objects are C11
> + *_s is C11
> + timespec_get is C11
>
> At least that's based on cppreference.com. Did I miss something?
>
> I agree a complete set of C99 methods is important.
>
> C11 adds some things which newlib should support and others which
> are the domain of the hosting environment. Newlib doesn't support
> pthreads for example (but has pthread.h) so C11 threads should
> follow the same pattern.
>
> > Cheers,
> > Andre
Yes I did, sorry for the noise. I am also chasing this up on gcc-patches 
ml as its related to an open issue:
https://gcc.gnu.org/ml/gcc-patches/2016-01/msg00925.html


I had categorized the missing functions into:
- Complex Arithmetic (which fall under the function_c99_math_complex class)
- floating-point environment
- Functions for greatest-width integer types
- atomics (missing atomic_is_lock_free and atomic_fetch_key)
- Bounds-checking interfaces

The last two are C11, as Szabolcs also pointed out in his reply:
https://gcc.gnu.org/ml/gcc-patches/2016-01/msg00934.html

So the missing C99 functions are the:
- Complex Arithmetic (all long double versions)
- Floating-point environment
- Functions for greatest-width integer types.

Cheers,
Andre