On Tue, 2 Sep 2025 17:49:28 GMT, Frederic Parain <[email protected]> wrote:
>> Since the removal of Q-types and the notion that nullability was not part of
>> the Java type, there was an awkward situation because nullable arrays of
>> value types and null free arrays of value types had each a different Java
>> mirror when they were in fact supposed to have the same Java type.
>> In order to accommodate to the new situation, that arrays can have
>> properties (nullability, flatness, atomicity, etc.) that are not part of
>> their Java type, the 1-1 relationship between the *ArrayKlass and the Java
>> mirror must be broken.
>> The proposed solution is to dedicate one instance of ObjArrayKlass to
>> represent the Java type of the array in the JVM, and have this instance
>> being the counterpart of the Java mirror of the array, and have several
>> instances of RefArrayKlass and FlatArrayKlass that represent the refinements
>> of the Java array type. Each RefArrayKlass/FlatArrayKlass encodes the
>> characteristic of a Java array for a given element type and a set of
>> properties.
>
> Frederic Parain has updated the pull request incrementally with one
> additional commit since the last revision:
>
> Forgot a TODO
src/hotspot/share/cds/archiveBuilder.cpp line 827:
> 825: num_obj_array_klasses ++;
> 826: type = "ref array";
> 827: } else if (k->is_objArray_klass()) {
Is this redundant? I think flat arrays union ref arrays = obj arrays?
src/hotspot/share/cds/cdsEnumKlass.cpp line 92:
> 90: }
> 91: oop oop_field = mirror->obj_field(fd.offset());
> 92: Klass* oop_field_klass = oop_field->is_objArray() ?
> oop_field->klass()->super() : oop_field->klass();
Hmm, what does this do? I assume `is_objArray` tests if something can be
converted to Java `Object[]`. In this case, CDS should check if the component
type of the array instead of the array supepr class, I think? The original code
did not call `super()`.
-------------
PR Review Comment:
https://git.openjdk.org/valhalla/pull/1452#discussion_r2317612466
PR Review Comment:
https://git.openjdk.org/valhalla/pull/1452#discussion_r2317611161
