RFR: 8295302: Do not use ArrayList when LambdaForm has a single ClassData [v3]

[Mandy Chung]

On Tue, 18 Oct 2022 05:21:47 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java line 346:
>> 
>>> 344: 
>>> 345:     /**
>>> 346:      * Returns an object to pass this.classData to the <clinit> method of the
>> 
>> What about:
>> 
>> Suggestion:
>> 
>>      * Returns the class data object that will be passed to `Lookup.defineHiddenClass`.
>>      * The classData is loaded in the <clinit> method of the generated class.
>>      * If the class data contains only one single object, this method returns  that single object.
>>      * If the class data contains more than one objects, this method returns a List.
>>      *
>>      * This method returns null if no class data.
>
> Actually, the classData is passed here:
> 
> 
>     private MemberName loadMethod(byte[] classFile) {
>         Class<?> invokerClass = LOOKUP.makeHiddenClassDefiner(className, classFile, Set.of())
>                                       .defineClass(true, classDataValues());
>         return resolveInvokerMember(invokerClass, invokerName, invokerType);
>     }
> 
> 
> So it doesn't go through `Lookup.defineHiddenClass`.

yes, it's an internal version that defines a hidden class, equivalent to calling `Lookup::defineHiddenClassWithClassData` (typo in my suggested wording), but it will bypass the security permission check and also returns the Class instead of Lookup (saving not to allocate a Lookup object).

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PR: https://git.openjdk.org/jdk/pull/10706