Re: Ada Microkernel?

["chris.danx" <chris.danx@ntlworld.com>]

>     What confounds me is how to provide system level calls for any
> C applications. Say I write my awesome Ada microkerenel, obviously
> I need to provide a C api if I want to use the GNU tools.

You don't need to have system level calls specifically for C applications, you
have system level calls for all applications (not just C ones).  There's nothing
special about C applications that means you have to have a special format for
them.  If i were you I'd make the API Ada styled (strongly typed and well
defined!  None of this "words are all you need" that you see in C based OS
api's.

The message passing systems used in microkernels (just one way of communication
possible) seem to work well.  I've decided to take the standard message passing
system(mailboxes) and try something that i've been told has been done in QNX and
Beos.  The idea is like pattern matching from functional languages and a bit
like dynamic typing.  It goes like this.

Module A sends a message to B to do X.

X can have more than one form, dependant on the types passed in.  You check the
types of the items passed in (each item must have a type descriptor accompanying
it) and X gives control to the appropriate routine.  If no routine is found you
get an error (haven't really got a good idea about how to handle this,
technically it should never happen but that doesn't mean it will never happen).
You might want to consider something like this in an OS if your doing one.

You could extend it to the API if you liked too.  (which is why i mentioned it).



Chris Campbell