Re: recalculating stack frames in Java 9

Hi Yanic, 

> De: "Yanic Inghelbrecht" <[email protected]>
> À: [email protected]
> Envoyé: Mercredi 21 Décembre 2016 15:11:35
> Objet: [asm] recalculating stack frames in Java 9

> Hi all,

> I'm wondering what other people are planning to do with regards to stack frame
> recalculation in Java 9.

> Having ASM do the recalculation instead of hand-crafting it is very convenient
> but needs the common superclass information.

> For me this is common-super-class calculation is one of the more worrying
> aspects of the new module system in Java 9, i.e. that the information might not
> be available to the instrumenting agent.
Agents are kings in Java 9, they can redefine a module 
http://download.java.net/java/jdk9/docs/api/java/lang/instrument/Instrumentation.html#redefineModule-java.lang.reflect.Module-java.util.Set-java.util.Map-java.util.Map-java.util.Set-java.util.Map- 
so give access to themselves. 

> I've seen two ways of getting it, either (force)load the relevant class and
> query it, or have ASM parse the ancestors' .class files (without actually
> loading them).

> Will these two ways still work with Java 9?
yes, 
within a module you can enforce a better control on the resources associated with that module with the exception that classfile (.class) are always accessible by anyone. 
see http://download.java.net/java/jdk9/docs/api/java/lang/ClassLoader.html#getResourceAsStream-java.lang.String- 

> As I understood it a couple of months ago, the file format for the new module
> system is deliberately left undocumented. And the forced-loading solution might
> not be possible either because of access restrictions on the module level.

> So unless I'm missing something, I would expect most libraries that depend on
> ASM for their bytecode manipulation will need a work-around for Java 9.

> So is there another way to get the common superclass information?

> Best regards,
cheers, 
Rémi 

> Yanic

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