On Thu, 15 Jul 2021 23:43:38 GMT, Vladimir Kozlov <k...@openjdk.org> wrote:
>> Sorry, I sent the wrong godbolt link: https://godbolt.org/z/1665fWzff > > @JornVernee I have small correct to your comment. We use simple inheritance > for Thread subclasses. Their instances have **one** vtbl pointer at the same > offset as in base class. But this pointer will point to separate vtable for > each subclass (and base class). The layout (sequence) of methods pointers in > vtable is the same in base class and subclasses. But subclass specific > methods pointers will be different. > > The only issue is that you have to make sure to cast passed object pointer to > correct subclass (or base class). Otherwise you will get incorrect vtable and > incorrect virtual methods pointers. > > R15 is used by our JIT compiled code and Interpreter code which are executed > only in JavaThread so the pinter it contains is JavaThread* Thanks Vladimir. This also matches what I was seeing in compiler explorer, but I wasn't sure if we could assume it always worked like that with every C++ compiler. It sound like R15 is expected to hold a `JavaThread*` though, so making the return type of `on_entry` be `JavaThread*` as David suggested seems correct. Thanks ------------- PR: https://git.openjdk.java.net/jdk17/pull/149
