RFR(XS) 8209823 Replace Verifier::load_class with a simple lookup of super classes

[dean.long at oracle.com]

On 8/27/18 4:02 PM, Ioi Lam wrote:
> https://bugs.openjdk.java.net/browse/JDK-8209823
> 8209823-simplify-verifier-load-class.v01/
>
> Please review this small clean up:
>
> Verifier::load_class(name) is called only when name is known to
> be the name of a super class of the current class. At this point,
> the super class should have already been loaded. Also, the loader
> of the current class should have already recorded the super
> class as a dependency.
>

I'm not an expert, so I have to ask:  is there a dependency from the 
current class to its "super supers" (its grandparent and higher)?  I 
believe the "super super" was resolved with "super" and the current 
class, but if there is no dependency from the current class to 
super->super or super->super->super, then wouldn't that allow a 
misbehaving classloader to return a different class for the load_class() 
call?

dl

> Therefore, load_class does a lot of work (such as resolving the
> super class by name) that's not necessary. Also, load_class is
> declared to potentially throw exceptions. This makes code analysis
> more complicated.
>
> The fix is to remove load_class() altogether and change
> ClassVerifier::name_in_supers to also return the super's.
> InstanceKlass*
>
> Thanks
> - Ioi