Extension functions were designed to return an error code -- there is even
a parameter in there definition which specifies which error codes they
return.  But due to a cut and paste typo, the extension function type
returns a void:

	typedef void (JNICALL *jvmtiExtensionFunction)
                (const jvmtiEnv* env,  ...);

this should be:


	typedef jvmtiError (JNICALL *jvmtiExtensionFunction)
                (const jvmtiEnv* env,  ...);