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From: Warren <ve3wwg@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Passing Ada Proc as a C Function Pointer
Date: Wed, 4 Aug 2010 17:55:44 -0700 (PDT)
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Date: 2010-08-04T17:55:44-07:00
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On Aug 4, 8:42=A0pm, Warren <ve3...@gmail.com> wrote:
..
> OTOH, I could create a Thread_Context that is larger than what
> the C routines expect. The Ada side will always be the one
> setting aside the Context and Stack space. So I suppose I could
> stuff an Ada procedure access (ptr) in it, and have a
> C convention proc (in Ada) invoke that, acting as the
> trampoline. =A0It just wastes a little more space but is
> simple to do.

Crap! That won't work either because the thread starting up
doesn't know its own context object location.  At least with
the current avr_threads API ;-)

I was trying to avoid modifying the avr_thread code. What it
really needs is a user_data parameter.

Hmmmm...

It seems it boils down to 3 choices:

1) Have the starting thread signal the called thread, when it has
"launched".
2) Add a "avr_get_current_thread" routine to return the current
context object.
3) Add a "avr_start_ada_thread" function, which provides the context
object as one of the local_proc arguments. The it can thunk with a
call to context.ada_access_ptr.all;

Only #1 works without changing the avr_threads C library.  Maybe I'll
try that approach first.

Warren