Running VM State - Modification, Complexity, Cleanliness
philippe at transvirtual.com
Mon Feb 12 09:43:50 PST 2001
you can find a pretty good description of Sun's VM implementation in the
following book. Sun is "very proud" and so will discuss/disclose almost
Kaffe is not very much documented. You can find some description of some of
its parts at
Philippe Laporte Tel: (510) 527-4025 ext 14
Transvirtual Technologies, Inc., Fax: (510) 559-3287
Berkeley, CA, USA. Email: philippe at transvirtual.com
Nathan Meyers wrote:
> On Mon, Feb 12, 2001 at 07:08:24AM -0800, Steve Sansha wrote:
> > Also: Does the Virtual Machine allow self-modifying
> > code? I'm sure it's possible for the bytecode to
> > create a new byte and use custom-built classloader
> > to actually load it, but is their an easier
> > alternative?
> > (I'm guessing it's not, since it's a type-safe
> > language)
> You may find a broken VM implementation that lets you do such a thing, but
> Java's pretty strict about access to memory. Writing into space occupied
> by loaded bytecodes isn't in spec. And, with the possibility that the code
> has been JITted, changing bytecodes on the fly would be very bad news.
> Custom classloaders are easy to write - there really is no "easier
> alternative". Loading your own manufactured bytecodes requires an almost
> trivial subclass of ClassLoader.
> > Also: I'm sending this to Kaffe because it seems to be
> > the best-documented, best-spirited VM... But just so I
> > know, are their any documents (except the in-source
> > code documentation) for Sun's reference
> > implementation? I've looked around and can't find
> > any.
> Sun publishes detailed specs about the language, the JVM, the classfile
> format, and such. As for details on JVM implementation - I doubt it. And
> that's a moving target anyway.
> > (Thanks * 1,000,000) -Steve
> > __________________________________________________
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