On Thu, 27 Oct 1994, Jeff Dalton wrote:
> In article <··········@peaches.cs.utexas.edu> ·······@cs.utexas.edu (David Gadbois) writes:
> >
> > .... But, IMHO, the main advantage was the
> >safety of the hardware/software environement -- you had to work really
> >hard to write code that would randomly corrupt and crash things.
>
> I wonder about this. I didn't use our Symbolics machine very
> much, but it did seem moderately easy to get it into an odd state.
> (Not nearly so easy as with D-machines.) Moreover, your Lisp code
> could do something that required a reboot. With an ordinary OS
> (Unix), your Lisp process might get messed up but everything else
> sailed on regardless.
I know what you mean. There are some things that will very readily crash
the LispM system, forcing a reboot. However, with a Symbolics you are
almost never in a position where you can't get any debug information even
in such cases, because of the FEP and the FEP debugger. This also makes
it possible to recover from things like running out of swap space, and to
debug things like race conditions that completely tie up Lisp without
crashing the system.
I guess it's a difference in focus. With a LispM, the Lisp environment
*is* your world, and everything is oriented around supporting it. With
Unix, Lisp is only one component of your world, and if it crashes, you
can still do something else. So in some sense it's OK for Lisp to crash
undebuggably.