Projects

Tue May 9 23:25:00 GMT 2000

"Boehm, Hans" wrote:
> I'm pretty sure you won't catch a Java compiler generating a .class file in
> which _Jv_MonitorEnter() and _Jv_MonitorExit() don't nest. The question is
> whether a hand generated .class file, or one generated by some non-Java
> compiler should compile correctly. According to the original version of
> "The Java Virtual Machine Specification", I believe the answer was "yes".
> Whether that has been changed, I don't know.

With the new JVM spec, the verifier is allowed to reject a class file in which
monitor operations do not nest. It does not have to reject such files, but
I know that for example the HotSpot VM will reject such class files. The
reason is that the HotSpot VM allocates monitor objects on the call stack, and
I beleive the HotSpot team did the lobbying to have this restriction in the VM
Spec. [a "locked object" also has it's gc info moved to the stack, so they
only need room for one word in each object to administer both]
-- Kresten
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