Kernel-space ctypes.h support?

[Sebastian Huber]

On 14/09/2018 18:57, Joel Sherrill wrote:
>
>
> On Fri, Sep 14, 2018 at 12:57 AM Sebastian Huber 
> <sebastian.huber at embedded-brains.de 
> <mailto:sebastian.huber at embedded-brains.de>> wrote:
>
>     On 14/09/2018 04:27, Joel Sherrill wrote:
>     >
>     >
>     > On Thu, Sep 13, 2018, 9:25 PM Chris Johns <chrisj at rtems.org
>     <mailto:chrisj at rtems.org>
>     > <mailto:chrisj at rtems.org <mailto:chrisj at rtems.org>>> wrote:
>     >
>     >     On 14/09/2018 10:13, Joel Sherrill wrote:
>     >     > On Thu, Sep 13, 2018, 5:40 PM Chris Johns
>     <chrisj at rtems.org <mailto:chrisj at rtems.org>
>     >     <mailto:chrisj at rtems.org <mailto:chrisj at rtems.org>>
>     >     > <mailto:chrisj at rtems.org <mailto:chrisj at rtems.org>
>     <mailto:chrisj at rtems.org <mailto:chrisj at rtems.org>>>> wrote:
>     >     >     On 14/09/2018 02:30, Joel Sherrill wrote:
>     >     >     > On Thu, Sep 13, 2018, 10:34 AM Sebastian Huber
>     >     >     > <sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>
>     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>>
>     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>
>     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>>>>
>     >     >     > wrote:
>     >     >     >     ----- Am 13. Sep 2018 um 14:07 schrieb joel
>     > joel at rtems.org <mailto:joel at rtems.org> <mailto:joel at rtems.org
>     <mailto:joel at rtems.org>>
>     >     >     <mailto:joel at rtems.org <mailto:joel at rtems.org>
>     <mailto:joel at rtems.org <mailto:joel at rtems.org>>>
>     >     >     >     <mailto:joel at rtems.org <mailto:joel at rtems.org>
>     <mailto:joel at rtems.org <mailto:joel at rtems.org>>
>     >     <mailto:joel at rtems.org <mailto:joel at rtems.org>
>     <mailto:joel at rtems.org <mailto:joel at rtems.org>>>>:
>     >     >     >
>     >     >     >     > On Thu, Sep 13, 2018, 3:28 AM Sebastian Huber <
>     >     >     >     > sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>
>     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>>
>     >     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>
>     >     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>
>     >     <mailto:sebastian.huber at embedded-brains.de
>     <mailto:sebastian.huber at embedded-brains.de>>>>> wrote:
>     >     >     >     >
>     >     >     >     >> Hello,
>     >     >     >     >>
>     >     >     >     >> I test currently the tqm8xx BSP which worked fine
>     >     until RTEMS 5. The
>     >     >     >     >> problem is that this BSP uses strtoul() to
>     get some
>     >     system
>     >     >     configuration
>     >     >     >     >> parameters from the boot loader. The Newlib
>     used by
>     >     RTEMS 5 has now
>     >     >     >     >> support for C locales in strtoul(). The C locale
>     >     support needs an
>     >     >     >     >> executing thread with a valid Newlib reentrancy
>     >     structure. This is
>     >     >     >     >> definitely not the case during bsp_start().
>     >     >     >     >>
>     >     >     >     >
>     >     >     >     > Why do we now longer have a global reentrancy
>     >     structure to fall back on?
>     >     >     >
>     >     >     >     I think having a global reentrancy as a fall
>     back just
>     >     for the lowest
>     >     >     level
>     >     >     >     system start without an idle thread is a bit of
>     overkill.
>     >     >     >
>     >     >     >     The heavy weight C local support which was recently
>     >     introduced in
>     >     >     Newlib is
>     >     >     >     not really the right thing for the embedded
>     systems I
>     >     know.  There were
>     >     >     >     several complaints about this on the Newlib mailing
>     >     list as well.  The
>     >     >     root
>     >     >     >     cause for this is the C standard. So, basically
>     the C
>     >     standard
>     >     >     strtoul() is
>     >     >     >     unsuitable for embedded systems. The FreeBSD
>     >     (sys/kern/strtoul.c) and
>     >     >     Linux
>     >     >     >     (lib/kstrtox.c) kernel have their own
>     implementations.
>     >     >     >
>     >     >     >
>     >     >     > FWIW the FACE Technical Standard does not include wide
>     >     characters in ANY
>     >     >     profile
>     >     >     > as of Edition 3.0. None of the RTOS vendors knew of any
>     >     avionics users. It
>     >     >     > wasn't viewed as a necessary feature. We could consider
>     >     disabling it by
>     >     >     default.
>     >     >     >
>     >     >
>     >     >     Is this something we could ot would want to control with
>     >     newlib via a config
>     >     >     option?
>     >     >
>     >     >
>     >     > We don't turn on locale for h8, m32c and maybe not epiphany. I
>     >     am pretty sure.it <http://sure.it> <http://sure.it>
>     >     > <http://sure.it> is an option. And should be a documented RSB
>     >     option to turn it
>     >     > back on. Should be a size savings for most users.
>     >
>     >     We turn on or off as an option?
>     >
>     >
>     > Based on Sebastian's observation, I think off.
>     >
>     > Does this impact wide characters and multibyte?
>     >
>     > We will need to document the impact. I suspect it removes some
>     POSIX
>     > support in a base build.
>
>     This problem with the C locale support used in strtoul() has
>     absolutely
>     nothing to do with the wide character or iconv() support.
>
>     Currently it is not possible to disable the C locale support in
>     Newlib.
>     Would such an option be the preferred way instead of a custom
>     strtoul()
>     etc. API and implementation?
>
>
> I think so. It would result in smaller footprint which is desirable for an
> unlikely to be used feature.
>
> I would like to know the impact of only having a single default locale 
> though.

It seems there is already some work in progress in this direction:

https://sourceware.org/ml/newlib/2018/msg00889.html

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
PGP     : Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.