Re: C99 support in Newlib

[Joel Sherrill <joel dot sherrill at oarcorp dot com>]

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

--
Joel Sherrill, Ph.D.             Director of Research & Development
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