Re: Passing Ada Proc as a C Function Pointer

[Rolf <rolf.ebert_nospam_@gmx.net>]

On 5 Aug., 02:45, Warren <ve3...@gmail.com> wrote:
> On Aug 4, 3:46 pm, Simon Wright <si...@pushface.org> wrote:
>
> > I would be a bit worried about Thread_Proc's *Ada* environment. There's
> > this thing called the Secondary Stack, used for - for example - string
> > catenation; and it's not set up here.
>
> Yikes, that could be a problem. I vaguely remember something about
> a "secondary stack".  I'm going to need to research this.

The current version of AVR-Ada does not support the secondary stack.
It is required for returning unconstrained objects from functions.
Using unconstrained arrays already consumes so much of the valuable
RAM that I never felt the need to support returning these objects from
functions.

BTW, GNAT-AVR (GPL 2010) from Adacore supports the secondary stack
(and some other Ada features currently missing in AVR-Ada).

> > I think you'll be OK so long as you restrain yourself! Twiddling LEDs
> > should be OK.

You can write quite complex programs without returning unconstrained
objects!

>
> Well LED twiddling is just the "hello world" test.  I hope to do
> a lot more than that, down the road!
>
> > There may be a pragma to prevent secondary stack usage?
>
> I'm all ears! ;-)

pragma Restrictions (No_Secondary_Stack);

It is already active if you use AVR-Ada.  See the file gnat.adc

    Rolf