RE: [cp-patches] FYI: ClassLoader caching Part 2

[Mark Wielaard]

On Mon, 2005-07-25 at 17:55 +0200, Jeroen Frijters wrote:
> > This won't work if you make the VM_USE_CACHE field static final. Then
> > the constant will be compiled into ClassLoader making it impossible to
> > override for the runtime vm-classes later. It has to be a 
> > static method for that to work.
> 
> Like Archie says, your comment doesn't make sense ;-) If a VM decides
> not to use the cache in ClassLoader, it replaces VMClassLoader and sets
> the constant to true.

Yes, but unfortunately that doesn't change the byte-code of the
ClassLoader class. static final primitive (and String) field values are
actually inlined into other classes. So you can replace VMClassLoader
all you want with a version the has VM_USE_CACHE set to another value,
that won't actually change the ClassLoader code paths unless ClassLoader
is also recompiled against this new value. Really, try it out. It is an
annoying byte code optimization. So for things that can be different at
runtime like the VMClasses you unfortunately cannot use static final
fields of primitive types.

> I haven't looked at jdwp yet, but hopefully jdwp will provide its own
> VM interface instead of messing around with the internals of other
> classes.

Yeah that would be the clean way to do it indeed.

Cheers,

Mark

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