> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Gerhard Fiedler
> Sent: Wednesday, February 22, 2006 9:45 PM
> To: piclist@mit.edu
> Subject: Re: [PIC] 2 questions about 18f4550
> 
> William Killian wrote:
> 
> > Many compilers designed for embedded or even not allow you to
eliminate
> > most of the traditional stack frame through optimization phases.
One
> > could write a C derivative with an extension for embedded work where
a
> > new keyword would allow a function to be defined as a tasks or reset
> > condition entry point that is not called but instead branched to
that
> > can not return.
> 
> I had a little parsing problem with these two sentences, but maybe
this is
> pertinent :)
> 
> Some PIC compilers are non-standard in that they don't use a real
stack;
> they create a static stack (and therefore a static call tree). This
limits
> some features, but it makes it easily possible that functions that are
> called only once are not called, but jumped into, and they don't use a
> return, but also a jump out.

PICs with their very small RAM space are not really suitable for
standard C approach.  Thus the unusual call and return approach.  But
nothing in the C definition requires the actual call and return assembly
instructions be used.  As long as it works enough like call and return
it is okay.

There is an ISO committee working on a standard embedded extension for
ISO C (mostly supplanting ANSI C as we're all globalized now and don't
need American ownership of the process.  Did you know that?  Thought you
might.)

An extension could be something like 'no_return' as in use entry instead
of no-return for a function that starts off the whole processor for
reboot or any task that can not return - for multi-tasking systems any
of the task entry points. Another extension could be forcing this
'function' to an absolute address.  That embedded committee is putting
in things to allow memory partitioning so that might very well be
enough.

Something like:
  noreturn reset (void)
  {
    /* do system init stuff */
    or (;;)
    {
      main_body();
    }
  }



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