RFR: 8230501: Class data support for hidden classes [v4]

[Jorn Vernee]

On Fri, 20 Nov 2020 20:23:27 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 2148:
>> 
>>> 2146:          * (unlike private static fields that are accessible to nestmates).
>>> 2147:          * Care should be taken w.r.t. mutability for example when passing
>>> 2148:          * an array or other mutable structure through the class data.
>> 
>> I don't think it's necessarily clear _why_/_how_ care should be taken from this text. I suggest:
>> Suggestion:
>> 
>>          * Care should be taken w.r.t. mutability for example when passing
>>          * an array or other mutable structure through the class data. Such
>>          * a constant should not be mutated, as downstream consumers of
>>          * this constant, such as other constants, are not guaranteed to see
>>          * the updated value, depending on the timing of their resolution.
>
> What about:
> 
> --- a/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
> +++ b/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
> @@ -2156,8 +2156,10 @@ public class MethodHandles {
>           * (unlike private static fields that are accessible to nestmates).
>           * Care should be taken w.r.t. mutability for example when passing
>           * an array or other mutable structure through the class data.
> -         * If you use a {@code List}, it is a good practice to make it unmodifiable
> -         * for example via {@link List#of List::of}.
> +         * Changing any value stored at the class data at runtime may lead to
> +         * unpredictable behavior.
> +         * If the class data is a {@code List}, it is a good practice to make it
> +         * unmodifiable for example via {@link List#of List::of}.
>           *
>           * @param bytes     the class bytes
>           * @param classData pre-initialized class data

Looks good!

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PR: https://git.openjdk.java.net/jdk/pull/1171