Nest host validation vs NestHost attribute performed by Lookup::defineHiddenClass

Mandy Chung mandy.chung at oracle.com
Tue Oct 1 18:04:22 UTC 2019



On 10/1/19 3:11 AM, Peter Levart wrote:
> Imagine a situation where a hidden class HC1 is defined in it's own 
> nest. Then this HC1 is used as a LC in a Lookup to define another 
> hidden class HC2 to be part of this nest (HC1, HC2). What should 
> HC2.getNestHost() return? If it returns HC1, then HC2 is effectively 
> preventing HC1 to be unloaded.
>

There is no restriction what a hidden class can call, for example, using 
lambda or method reference, which may call a framework library to 
generate HC2.  HC1 and HC2 should be unloaded when both classes become 
unreachable.   Do I miss the issue you tried to point out?

(Note that defineHiddenClass takes an enum constant to specify if the 
hidden is a dynamic nestmate and/or a weak class to specify if it's 
weakly referenced by the class loader.  In other words, a dynamic 
nestmate has the same lifecycle as its defining class loader if not 
specified weak.)

Mandy


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