On Mon, 18 Aug 2025 18:11:11 GMT, Dan Heidinga <[email protected]> wrote:
>> This PR loads the classes for the boot/platform/app loaders with
>> `AOTLinkedClassBulkLoader::preload_classes()`. This happens at the very
>> beginning of `vmClasses::resolve_all()`, before any Java code is executed.
>>
>> - We essentially iterate over all the classes inside the
>> `AOTLinkedClassTable` and adds them into the system dictionary using the new
>> method `SystemDictionary::preload_class()`.
>> - `SystemDictionary::preload_class(..., k)` is lightweight because it's
>> called in a single thread after all super types of `k` have been loaded. So
>> most of the complicated work (such as place holders, circularity detection,
>> etc) in `SystemDictionary::resolve_or_null(..., k)` can be skipped. We also
>> don't need to call into `ClassLoader::load_class()` as the boot/platform/app
>> loaders are well-behaved.
>> - In the assembly phase, we record the mirror, package, protection domain,
>> code source, etc, of these classes. So there's no need to programmatically
>> create them in the production run. See `HeapShared::copy_java_mirror()` and
>> also changes in ClassLoader.java and SecureClassLoader.java.
>
> src/hotspot/share/cds/aotLinkedClassBulkLoader.cpp line 96:
>
>> 94: // later in load_javabase_classes() and load_non_javabase_classes().
>> 95:
>> preload_classes_in_table(AOTLinkedClassTable::for_static_archive()->boot1(),
>> "boot1", Handle(), CHECK);
>> 96:
>> preload_classes_in_table(AOTLinkedClassTable::for_static_archive()->boot2(),
>> "boot2", Handle(), CHECK);
>
> why do we maintain both a `boot1` and `boot2` set here when both are loaded
> before executing any Java code? Is the distinction meaningful for preloaded
> classes given both are loaded into the same classloader?
This is still meaningful as the `boot1` classes from the dynamic CDS archive
are still loaded at the end of `vmClasses::resolve_all()`, after some bytecodes
are executed.
> src/hotspot/share/cds/cdsHeapVerifier.cpp line 241:
>
>> 239: }
>> 240: if (field_ik == vmClasses::Boolean_klass()) {
>> 241: // TODO: check if is TRUE or FALSE
>
> Are we canonicalizing Boolean.TRUE & Boolean.FALSE and thus don't care if a
> static field points to them? And Boolean.TYPE isn't getting the same
> treatment?
Yes.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/26375#discussion_r2292643055
PR Review Comment: https://git.openjdk.org/jdk/pull/26375#discussion_r2292643019
