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Re: [DotGNU]Register Based VM's Q.

From: Rhys Weatherley
Subject: Re: [DotGNU]Register Based VM's Q.
Date: Tue, 14 Aug 2001 21:22:25 +1000

Scott Lanham wrote:

> So is a VM assumed to have a flat memory space?
> [...] I guess there must be some issue with using this kind of model with a
> VM? I
> always did like the 386's protection mechanisms :-P

It all depends on what you are trying to acheive.  C# and
Java have a very strict form of security: they are not only
memory-safe (as the 386 is), but also type-safe (which
the 386 isn't).

A VM with a flat address space is fairly easy to isolate
from the rest of the world, but the program is only safe from
the rest of the world.  It isn't safe from itself.  e.g. buffer
overruns, type unsafe operations, etc.

Internet C++ seems to be based on this kind of approach.
Nothing wrong with it, except it won't work for IL,
which requires strict type-safety.

There are two gcc problems that need to be solved by
DotGNU: compile to IL, and compile to some "to be
defined" engine.  If we are willing to sacrifice type
safety, then gcc becomes really easy to port.  If
we want to do IL, things become hard.



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