RFR: 8301220: Return value of toArray() of Сollection types from java.base should be trusted [v3]

[ExE Boss]

On Mon, 30 Jan 2023 03:13:01 GMT, Glavo <duke at openjdk.org> wrote:

> > > > Why not use set of classes?
> > > 
> > > 
> > > Because some classes are not visible here (such as `Arrays.ArrayList`).
> > > I'm not sure what the best choice is, so I'm trying to explore the implementation plan.
> > 
> > 
> > Only `Arrays.ArrayList` is not visible here. You can change it to package-private.
> 
> Another problem is that use set of classes may cause unnecessary classes to be loaded, which has a negative impact on startup speed. I want to do some tests in the next few days.

Class constants don’t cause class initialization, only bare‑bones loading (in case `NoClassDefFoundError` needs to be thrown).

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One option would be to move these sets into a method inner class, such as:

static boolean isTrustedCollection(Collection<?> coll) {
	final class Holder {
		private static final Set<Class<? extends Collection<?>>> TRUSTED_COLLECTIONS = Set.of(
			// ...
		);

		private static final Set<Class<? extends Map<?, ?>>> TRUSTED_MAPS = Set.of(
			// ...
		);
	}

	if (coll.getClass().getModule() == Object.class.getModule()) {
		if (coll instanceof CollectionWrapper wrapper) {
			return isTrustedCollection(wrapper.getCollection());
		}

		if (Holder.TRUSTED_COLLECTIONS.contains(coll.getClass().getName())) {
			return true;
		}

		if (coll instanceof ImmutableCollections.AbstractImmutableCollection<?>) {
			return true;
		}

		// Map keys set or entries set
		if (coll instanceof Set<?> && coll.getClass().isMemberClass()) {
			return Holder.TRUSTED_MAPS.contains(coll.getClass().getNestHost().getName());
		}
	}

	return false;
}

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PR: https://git.openjdk.org/jdk/pull/12212