RFR: 8340831: Simplify simple validation for class definition in MethodHandles.Lookup

[Chen Liang]

On Wed, 25 Sep 2024 10:02:37 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> `MethodHandles.Lookup` defines a `ClassFile` for simple validations; it is unnecessary and can be scalarized manually. The removal of `ClassFile` class is also slightly helpful for bootstrap by reducing class loading. Also improved class file version checking in `VM` class.
>
> src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 2276:
> 
>> 2274:                 var thisClass = cm.thisClass();
>> 2275:                 name = thisClass.asInternalName();
>> 2276:                 sym = thisClass.asSymbol();
> 
> We only use this for determining package name are equal, and sym.packageName() does the similar transformations plus a bit more. Likely not a significant cost compared to the `ClassFile::parse` - but perhaps there's room for a utility method to get the package name directly from an internal name?

This is not part of internal code path so I don't think it is that sensitive

> src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 2440:
> 
>> 2438:         }
>> 2439: 
>> 2440:         record ClassDefiner(Lookup lookup, String name, byte[] bytes, int classFlags, ClassFileDumper dumper) {
> 
> Rename `name` to `internalName`, dropping the explicit `internalName()` method.

Should I rename other existing name vars too?

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PR Review Comment: https://git.openjdk.org/jdk/pull/21170#discussion_r1775101786
PR Review Comment: https://git.openjdk.org/jdk/pull/21170#discussion_r1775102743