Re: Ada

[Chris Morgan <cm@mihalis.net>]

"Andy Glew" <glew@cs.wisc.edu> writes:

> > > If you can get C and Unix for free why do you need Ada and Ada-OS?
> 
> Just for my own knowledge: does GNU Ada (GNATS) support a full
> Ada-OS, including the real-time and multithreading constructs like
> rendezvous?  Do these run on stock hardware? On LINUX?

Full (i.e. strict) compliance with Ada semantics needs root privilege
on some OSs (e.g. Solaris last time I checked) so that your threads
can get true pre-emptive multi-threading (e.g. by running in the
real-time rather than time-sharing scheduling priority
class). Otherwise (again on Solaris, last time I checked) there are
things like threads going to the back of their queue after being
pre-empted by a higher priority thread, which is incorrect for true
pre-emption (it looks to the thread like it got preempted by a
"sibling"). On the other hand you can even chose user-space or kernel
threads. There is some advanced work on this stuff going on at FSU
e.g. to make user-space threads more useful by letting another thread
work when one blocks on I/O.

Additionally the GNAT compiler has lots of other goodies. Check out
www.gnat.com and www.gnuada.org for some nice starting points. Markus
Kuhn at Cambridge has implemented a candidate Serpent (some crypto
scheme) implementation in Ada, don't know how it did.

The above is probably garbled (long day) hope it give you some idea.

Chris
-- 
Chris Morgan <cm at mihalis.net>                  http://mihalis.net