ANN: Cortex GNAT RTS 20180419

ANN: Cortex GNAT RTS 20180419

[Simon Wright]

There are three parallel releases at Github[1], for

* GNAT GPL 2016/GCC 6
* GCC 7
* GNAT GPL 2017

(three, because of changes to the interface between the compiler and the
RTS).

There's not much user-visible change from the last GCC 7 release[2],
except that all but 2k of free store is available for the heap (the 2k
is used for startup and interrupt stack).

[1] https://github.com/simonjwright/cortex-gnat-rts/releases
[2] https://github.com/simonjwright/cortex-gnat-rts/releases/tag/r20171016

Re: ANN: Cortex GNAT RTS 20180419

[Jere]

On Saturday, April 28, 2018 at 12:13:14 PM UTC-4, Simon Wright wrote:
> There are three parallel releases at Github[1], for
> 
> * GNAT GPL 2016/GCC 6
> * GCC 7
> * GNAT GPL 2017
> 
> (three, because of changes to the interface between the compiler and the
> RTS).
> 
> There's not much user-visible change from the last GCC 7 release[2],
> except that all but 2k of free store is available for the heap (the 2k
> is used for startup and interrupt stack).
> 
> [1] https://github.com/simonjwright/cortex-gnat-rts/releases
> [2] https://github.com/simonjwright/cortex-gnat-rts/releases/tag/r20171016

Thank you so much for keeping these up to date.  Question:
Do you have any suggestions for pulling out a ZFP from this repo?  I know
it isn't setup for that, but was curious if you had any tips for what
to mainly look for.  I'm not so much worried about changing the ada files,
but I am more interested in what types of changes (if any) should I be
looking to do to the ld file, the gpr file, the xml file, etc.  So mostly
the build system.  I'm probably gonna try and mod the ardiuno one as it
is closest to my chip (an M0+).  Right now, I have been pulling from one
of your older revisions where the ZFP was still available.

Also, 2 other questions:
If I do get something working, do I use your licensing statement in the
files as is, or should I modify it if I modify the files?  I do plan
on modifying quite a few of the ada ones to fit with my chip, but I had
noticed you seemed to use the vanilla FSF copyright in your license
statement, even though I assume you wrote some of the code in the file.

It looks like you most likely use gcc for some intrinsics like memcpy. 
Do I need to worry about licensing issues if I build with GNAT GPL 2017 
using a modified version of your RTS if it links in functions like memcpy?
I can supply my own if so, they just won't be as efficient if I do.

Re: ANN: Cortex GNAT RTS 20180419

[Simon Wright]

Jere <jhb.chat@gmail.com> writes:

> On Saturday, April 28, 2018 at 12:13:14 PM UTC-4, Simon Wright wrote:
>> There are three parallel releases at Github[1], for
>>
>> * GNAT GPL 2016/GCC 6
>> * GCC 7
>> * GNAT GPL 2017
>>
>> (three, because of changes to the interface between the compiler and the
>> RTS).
>>
>> There's not much user-visible change from the last GCC 7 release[2],
>> except that all but 2k of free store is available for the heap (the 2k
>> is used for startup and interrupt stack).
>>
>> [1] https://github.com/simonjwright/cortex-gnat-rts/releases
>> [2] https://github.com/simonjwright/cortex-gnat-rts/releases/tag/r20171016
>
> Thank you so much for keeping these up to date.  Question:
> Do you have any suggestions for pulling out a ZFP from this repo?  I know
> it isn't setup for that, but was curious if you had any tips for what
> to mainly look for.  I'm not so much worried about changing the ada files,
> but I am more interested in what types of changes (if any) should I be
> looking to do to the ld file, the gpr file, the xml file, etc.  So mostly
> the build system.  I'm probably gonna try and mod the ardiuno one as it
> is closest to my chip (an M0+).  Right now, I have been pulling from one
> of your older revisions where the ZFP was still available.

One you haven't mentioned is system.ads.

The barebones site https://wiki.osdev.org/Ada_Bare_bones wants you to
put the restrictions in gnat.adc; personally I've put them in
system.ads, that way you don't need to worry about whether your own code
will see the restrictions.

The ld script will need changing to match your board's memory map; also,
maybe, the ENTRY symbol. Not sure about the EXTERNs either.

You'll need to change runtime.xml to specify the right compiler switches
(when I give GCC8 -mcpu=cortex-m0plus it adds -mfloat-abi=soft -mthumb
-march=armv6-m automatically (from inspection of the .ali)).

build_runtime.gpr clearly won't need to reference FreeRTOS! and the
Source_Dirs will clearly change.

> Also, 2 other questions:
> If I do get something working, do I use your licensing statement in the
> files as is, or should I modify it if I modify the files?  I do plan
> on modifying quite a few of the ada ones to fit with my chip, but I had
> noticed you seemed to use the vanilla FSF copyright in your license
> statement, even though I assume you wrote some of the code in the file.

I used the FSF copyright because I've assigned copyright to the FSF
(#1016382). If you change something, I believe you can add your
copyright, so long as you redistribute on the same terms.

> It looks like you most likely use gcc for some intrinsics like memcpy.
> Do I need to worry about licensing issues if I build with GNAT GPL 2017
> using a modified version of your RTS if it links in functions like memcpy?
> I can supply my own if so, they just won't be as efficient if I do.

libgcc is used for things such as long addition, multiplication etc not
supported by the hardware.

GCC uses functions normally supplied by libc as discussed in [1]. The
only part of the RTS that this affects is Startup, in

      --  Copy data to SRAM
      Data_In_Sram := Data_In_Flash;
      --  Initialize BSS in SRAM
      Bss := (others => 0);

(the second array assignment uses memset()).

You could change this to do byte-by-byte copy (AdaCore's RTSs do this in
assembly) but of course your own code (and even libgnat) might use the
libc functions (Interfaces.C uses memcpy), and there is no way I can see
to tell GCC not to do this.

Of course you could build your own, but I've got round this by using
newlib. ISTR writing up how to build newlib for GNAT GPL, but where...?
Anyway, I'm currently using newlib 2.5.0 and building as in [2]. I
_think_ the gpl branch would do the job. FYI, newlib works out what cpu
versions to build from the compiler capabilities, as reported by e.g.
arm-eabi-gcc -print-multi-lib.

[1] https://docs.adacore.com/gnathie_ug-docs/html/gnathie_ug/gnathie_ug/using_gnat_pro_features_relevant_to_high_integrity.html#array-and-record-assignments-and-the-high-integrity-profiles
[2] https://sourceforge.net/u/simonjwright/buildingarmeabi/code/ci/default/tree/

Re: ANN: Cortex GNAT RTS 20180419

[Jere]

On Sunday, April 29, 2018 at 7:51:02 AM UTC-4, Simon Wright wrote:
> Jere  writes:
> 
> > On Saturday, April 28, 2018 at 12:13:14 PM UTC-4, Simon Wright wrote:
> >> There are three parallel releases at Github[1], for
> >>
> >> * GNAT GPL 2016/GCC 6
> >> * GCC 7
> >> * GNAT GPL 2017
> >>
> >> (three, because of changes to the interface between the compiler and the
> >> RTS).
> >>
> >> There's not much user-visible change from the last GCC 7 release[2],
> >> except that all but 2k of free store is available for the heap (the 2k
> >> is used for startup and interrupt stack).
> >>
> >> [1] https://github.com/simonjwright/cortex-gnat-rts/releases
> >> [2] https://github.com/simonjwright/cortex-gnat-rts/releases/tag/r20171016
> >
> > Thank you so much for keeping these up to date.  Question:
> > Do you have any suggestions for pulling out a ZFP from this repo?  I know
> > it isn't setup for that, but was curious if you had any tips for what
> > to mainly look for.  I'm not so much worried about changing the ada files,
> > but I am more interested in what types of changes (if any) should I be
> > looking to do to the ld file, the gpr file, the xml file, etc.  So mostly
> > the build system.  I'm probably gonna try and mod the ardiuno one as it
> > is closest to my chip (an M0+).  Right now, I have been pulling from one
> > of your older revisions where the ZFP was still available.
> 
> One you haven't mentioned is system.ads.
> 
> The barebones site https://wiki.osdev.org/Ada_Bare_bones wants you to
> put the restrictions in gnat.adc; personally I've put them in
> system.ads, that way you don't need to worry about whether your own code
> will see the restrictions.
> 
> SNIPPED...
> 
> You could change this to do byte-by-byte copy (AdaCore's RTSs do this in
> assembly) but of course your own code (and even libgnat) might use the
> libc functions (Interfaces.C uses memcpy), and there is no way I can see
> to tell GCC not to do this.
> 
> Of course you could build your own, but I've got round this by using
> newlib. ISTR writing up how to build newlib for GNAT GPL, but where...?
> Anyway, I'm currently using newlib 2.5.0 and building as in [2]. I
> _think_ the gpl branch would do the job. FYI, newlib works out what cpu
> versions to build from the compiler capabilities, as reported by e.g.
> arm-eabi-gcc -print-multi-lib.
> 
> [1] https://docs.adacore.com/gnathie_ug-docs/html/gnathie_ug/gnathie_ug/using_gnat_pro_features_relevant_to_high_integrity.html#array-and-record-assignments-and-the-high-integrity-profiles
> [2] https://sourceforge.net/u/simonjwright/buildingarmeabi/code/ci/default/tree/

Thank you very much.  I currently supply the byte by byte copy.  I don't have 
any experience using newlib, but I'll take a look.  Thanks again for all your 
hard work.

Re: ANN: Cortex GNAT RTS 20180419

[Simon Wright]

Simon Wright <simon@pushface.org> writes:

> ISTR writing up how to build newlib for GNAT GPL, but where...?

https://github.com/simonjwright/cortex-gnat-rts/wiki/WorkingWithGnatGPL