Offline instrumentation and external field holder

[tvale]

Hi Guy,

Can you provide insight as to why you use an external class to hold the bytecode-injected fields in the offline instrumentation?

Thanks,
Tiago.

[fmcarvalho]

The “bytecode-injected fields” that you are referring to, are static final fields initialized with fields’ addresses obtained through the sun.misc.Unsafe.

Yet, remember that you cannot invoke the sun.misc.Unsafe on the JVM bootstrap.

So, if you had the “bytecode-injected fields” in the own transactional class, then you could not instrument any of the Java RT classes that are loaded during the bootstrap, otherwise it would crash.

So, the external class is a workaround to avoid this situation, because it is only referred by transactional methods that are not invoked during the JVM bootstrap.