RFR: 8078641: MethodHandle.asTypeCache can retain classes from unloading [v2]

[Vladimir Ivanov]

On Wed, 1 Sep 2021 17:28:37 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address review comments
>
> src/java.base/share/classes/java/lang/invoke/MethodHandle.java line 926:
> 
>> 924:     /* Returns true when {@code loader} keeps {@code cls} either directly or indirectly through the loader delegation chain. */
>> 925:     private static boolean keepsAlive(Class<?> cls, ClassLoader loader) {
>> 926:         return keepsAlive(cls.getClassLoader(), loader);
> 
> Suggestion:
> 
>         ClassLoader defLoader = cls.getClassLoader();
>         if (isBuiltinLoader(defLoader)) {
>             return true; // built-in loaders are always reachable
>         }
>         return keepsAlive(defLoader, loader);
> 
> 
> I think it's clearer to check if `cls` is not defined by any builtin loader here and then check if `loader` keeps `cls` alive.
> 
> So `keepsAlive(ClassLoader loader1, ClassLoader loader2)` is not needed and replace line 935 and 940 to `keepsAlive(Class, ClassLoader)` instead.

Sounds good. 

Incorporated your suggestions along with some minor refactorings.

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PR: https://git.openjdk.java.net/jdk/pull/5246