hotspot-dev Digest, Vol 24, Issue 33

Dan Hicks danhicks at
Mon Apr 27 14:44:13 PDT 2009

This isn't a new development.  Over the years I've run into several JVM 
architectural details that are documented only in the JLS, and others 
that are documented nowhere other than in the JCKs.  The JVM Spec is 
incomplete in many ways.
> Date: Mon, 27 Apr 2009 22:38:05 +0100
> From: Jeffrey Sinclair <jeff at>
> Subject: Re: invokevirtual on package private override in different
> 	classloader
> To: Karen Kinnear <Karen.Kinnear at Sun.COM>
> Cc: Alex Buckley <Alex.Buckley at Sun.COM>, John.Rose at Sun.COM,
> 	hotspot-dev at,	David Holmes - Sun Microsystems
> 	<David.Holmes at Sun.COM>
> Message-ID: <1240868285.6044.70.camel at Lini>
> Content-Type: text/plain; charset="UTF-8"
> Hi Karen,
> There are no languages that I'm specifically involved in, I would love
> to some day get involved more heavily in either the JVM or the language
> specification. At the moment I'm just your standard Java developer with
> an interest in this.
> Apologies for causing trouble, I admit that I'm being very picky here
> and perhaps unnecessarily picky. The issue I have is that before this
> amendment, the resolution could be read without having to understand the
> language at all.
> Now the amendment has included the word 'override' which I believe is a
> language feature because it is not defined in the vm specification
> outside of the condensed chapter on the Java Programming Language
> Concepts.
> If I were to write an implementation of the JVM, I now need to
> understand the behaviour of override which in itself is tied into a
> specific language specification version. Hence the JVM now has a
> dependency on the language in order to deal with package private
> matching signatures in different runtime packages (and in fact now for
> any method resolution).
> For example, what is permitted as an 'override' means something
> different between Java 1.4 and Java 5 due to covariant return types.
> Let me know if my point is not clear or is incorrect.
> Regards,
> Jeff
Dan Hicks
Man is born to live, not to prepare to live.  --Boris Pasternak

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