POSIX Compilance- #2966, GSoC Project 2019

[Vaibhav Gupta]

On Sun, Mar 17, 2019 at 9:43 PM Joel Sherrill <joel at rtems.org> wrote:

>
>
> On Sat, Mar 16, 2019, 2:49 PM Vaibhav Gupta <vaibhavgupta40 at gmail.com>
> wrote:
>
>> Hello,
>> As mentioned by Dr Joel that high priority is to be given to
>> implementations missing in FACE GPP 3.0.
>> So, I have got FACE Technical Standard 3.0 pdf downloaded. And its pretty
>> easy to compare tickets now.
>>
>
> The FACE Technical Standard is a long and sleep inducing read. :)
>
> We have a POSIX Compliance document which tracks RTEMS vs various POSIX
> profiles. Many standards have POSIX profiles. SCA is for software radios.
> FACE TS was designed for cockpit software. Use the compliance document for
> ease:
>
> https://docs.rtems.org/branches/master/posix-compliance/index.html
>
Thanks, I guess this document contains the list of methods that are already
supported. I was comparing tickets with FACE to find which all are still in
need to be addressed.


>
> I track compliance against every standard I can find.
>
This is best for RTEMS

>
> FYI I have supported the FACE Consortium for a number of years in various
> roles.
>
>
>
> .
>> And while exploring big picture I got many questions:
>>
>> 1 - It is mentioned in the ticket #2966, *"RTEMS POSIX Compliance is
>> achieved via a combination of methods and .h files in RTEMS and the newlib
>> C Library."* .
>> So, if a method or a header is present in Newlib C, it is not required to
>> be present in RTEMS library? But that would mean Newlib is directly ported
>> to RTEMS.
>>
>
> POSIX includes the entire C Library in its definition. Newlib is our C
> Library so if the method makes sense to be there, we add it to Newlib.
>
> In general, threading and synchronisation go in RTEMS. But ask for
> specific methods. It isn't always obvious.
>
>
>
>
>> .
>>
>> *> I had an off-list talk with Vijay, he proved to be very helpful. I
>> asked him same question (question 1), I would like to conclude what we
>> discussed. *
>>
>> *> He told that "RTEMS uses its own version of Newlib C as it cannot
>> directly mirror original Newlib as, if methods change the way it works,
>> they can break RTEMS".*
>>
>>
>> *> But then my doubt was, if that's the case, why keep modified headers
>> of original Newlib under separate Newlib C folder in RTEMS? Why not
>> directly include them in RTEMS library? (As I found newlib-1d35a003f.tar.gz
>> in {RTEMS-ROOT}/rsb/rtems/sources/    )*
>> *.*
>> *> To which he replied,  "RTEMS version of newlib is being used as a
>> libraby of RTEMS only and the posix functions are being linked to this
>> newlib"*
>> .
>> 2- So, My second doubt is that our target is to contribute to Newlib C or
>> RTEMS Library? Or we will add methods to Newlib C and link them to RTEMS?
>>
>> Thanks
>> Vaibhav Gupta
>>
>
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