Re: ANN: Cortex GNAT RTS 2018-07-15

[Simon Wright <simon@pushface.org>]

Paul Rubin <no.email@nospam.invalid> writes:

> Simon Wright <simon@pushface.org> writes:
>>         freertos...
>
> I took a look at the freertos source code: the common kernel is 3
> files total around 10 KLOC of C, though a lot of it is conditionally
> compiled based on feature flags.  It's about what you'd expect in an
> RTOS, i.e.  very low level, lots of pointer banging, critical
> sections, etc.
>
> I wonder whether it's feasible to write something like that in Ada, with
> just a few calls to intrinsics for stuff like interrupts.  Any thoughts?
> It seems like a shame to have that much C code at the bottom of an Ada
> application.

FreeRTOS has the advantage of existing, with many targets, with the
possibility of support, with options such as file systems & networking,
and being libre.

At the time I started with Cortex GNAT RTS, aside from it being an
interesting project, there was quite a lot of chat about the fact that
GNAT GPL (now CE) was pure GPL. I was also familiar with GNAT's
VxWorks(5.3) target, also running over an RTOS, so running over an RTOS
was quite natural.

I agree that a considerable chunk of FreeRTOS could probably be replaced
by straightforward Ada code, but that'd be someone else's project!

The RTOS part of AdaCore's embedded Ravenscar RTOSs (s-bb*.ad?) is about
5500 lines (1250 semicolons) of Ada.