#4328: New APIs added to POSIX Standard (2021)

[Joel Sherrill]

Keep devel@ on the list. :)

On Fri, Mar 19, 2021 at 7:51 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:

> Sir,
>
> Thank you for the link! I see that you're right, those last four are
> in newlib, plus memmem(). I updated those in the Google Sheet.
>
> Now I see the newlib part, but where are you referring to specifically
> when you say RTEMS, as in "POSIX support comes from a mix of RTEMS and
> newlib"?
>

POSIX is a HUGE HUGE standard and references other standards. One
it references and pulls in is the C99 Standard C Library which is libc and
libm. RTEMS mostly does not implement this functionality and relies on
another open source project for those APIs. Newlib is an open source
C Library used by RTEMS, Cygwin, and most embedded systems GNU tools
chains.

Most of the POSIX header files with RTEMS are actually in Newlib even
if they originated with RTEMS. Many are shared with Cygwin.

So methods like the string, memory, and *printf come from Newlib since they
are in C99. We provide POSIX like threading, signals, core file access, and
much more.

It's a complementary relationship but it takes a bit to figure out when
something should be in one or the other. The line gets blurred at times.

Say you added a new CPU architecture implementation of a math
method (like Eshan did last year), then it goes in newlib. But he also
added some POSIX methods which go in RTEMS. In either case,
we like tests for them in RTEMS to show they work in our environment.

--joel




> Thanks again!
>
> Matt
>
> On Fri, Mar 19, 2021 at 1:13 PM Joel Sherrill <joel at rtems.org> wrote:
> >
> >
> >
> > On Fri, Mar 19, 2021, 6:40 AM Joel Sherrill <joel at rtems.org> wrote:
> >>
> >>
> >>
> >> On Fri, Mar 19, 2021, 5:48 AM Matthew Joyce <mfjoyce2004 at gmail.com>
> wrote:
> >>>
> >>>
> https://docs.google.com/spreadsheets/d/1reCNOIZC5JTwQENgl-hvG8THfQqNtlUDVy_07PYodic/edit?usp=sharing
> >>>
> >>> Hello,
> >>>
> >>> As suggested by Dr. Sherril, I've taken an initial look through this
> >>> document https://www.opengroup.org/austin/docs/austin_1110.pdf and
> >>> added the new methods  to a Googe Sheet, linked above.
> >>>
> >>> None of them appear to be in the RTEMS POSIX API Users Guide, but
> >>> maybe that's not the right place to look. I'll stand by for your
> >>> feedback regarding what's possible / desirable to add to RTEMS.
> >>
> >>
> >> It is possible they are in our C Library or Math Library.  Or just not
> in the manual. The POSIX manual tends to be sparse since you can always use
> man pages or the POSIX standard.
> >>
> >> Since you have RTEMS and tools built. Find one of the libc.a and libm.a
> files in the tools install and librtemscpu.a in the RTEMS build or install.
> Then try a command something like this:
> >>
> >> CPU-rtems6-nm LIBRARY | grep SYMBOL
> >>
> >> If you see it list with T then it is in the text section and there.
> >
> >
> > Following up, I initially answered from my phone and didn't look at
> source.  I am still on my phone but looked through the list and think the
> last four methods are probably the only ones currently supported.
> >
> >
> https://sourceware.org/git/?p=newlib-cygwin.git;a=tree;f=newlib/libc/string;h=ceeec602cdd0e6b5c6b002b741bda9b41da4e441;hb=HEAD
> >
> > POSIX support comes from a mix of RTEMS and newlib. That's key to this
> type of project.
> >
> > --joel
> >>
> >>
> >>
> >>>
> >>> Thanks very much for your time!
> >>>
> >>> Sincerely,
> >>>
> >>> Matt
>
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