Review CSR JDK-8266760: Remove sun.misc.Unsafe::defineAnonymousClass

[Mandy Chung]

Hi Attila,

Thanks for the input.  I added the Nashorn use case in JDK-8212620.

Mandy

On 5/11/21 3:41 AM, Attila Szegedi wrote:
> I'm fine with the removal, although if you remember we use it in 
> Nashorn too[0], and when I tried to replace it with the hidden classes 
> facility the issue we run into was that hidden classes' methods didn't 
> show up in stack traces the way anonymous classes' methods did[1]. 
> Since Nashorn uses anonymous classes to install compiled JavaScript 
> application code, it is important to be able to report stack traces 
> from them. It unfortunately can't just use StackWalker, as it has to 
> post-edit traces of already thrown exceptions.
>
> So ensuring JDK-8212620 is implemented as well, and/or maybe having 
> a MethodHandles.Lookup.ClassOption to specify the class should show up 
> in stack traces would be important to implement alongside the removal. 
> It's not a show-stopper, Nashorn will be able to gracefully fail over 
> to ordinary class loading in absence of anonymous class loading, but 
> I'd really like to be able to transition to using hidden classes if we 
> could get them to show up in stack traces.
>
> Attila.
>
> [0] 
> https://github.com/openjdk/nashorn/blob/main/src/org.openjdk.nashorn/share/classes/org/openjdk/nashorn/internal/runtime/Context.java#L329 
> <https://urldefense.com/v3/__https://github.com/openjdk/nashorn/blob/main/src/org.openjdk.nashorn/share/classes/org/openjdk/nashorn/internal/runtime/Context.java*L329__;Iw!!GqivPVa7Brio!LQB5qhHavp8DtWhCLdw4CJAYuNYZhhEGY65H9uA3sx_xqMOriXmvlH9VQibTLkCtHQ$>
> [1] 
> https://mail.openjdk.java.net/pipermail/nashorn-dev/2020-October/007578.html 
> <https://mail.openjdk.java.net/pipermail/nashorn-dev/2020-October/007578.html>
>
> On Tue, May 11, 2021 at 1:03 AM Mandy Chung <mandy.chung at oracle.com 
> <mailto:mandy.chung at oracle.com>> wrote:
>
>     Thank you all.
>
>     Mandy
>
>     On 5/10/21 2:27 PM, Paul Sandoz wrote:
>     > Looks good, I took the liberty of making some minor edits,
>     mostly fixing some typos.
>     >
>     > Paul.
>     >
>     >> On May 10, 2021, at 12:26 PM, Mandy Chung
>     <mandy.chung at oracle.com <mailto:mandy.chung at oracle.com>> wrote:
>     >>
>     >> Hidden classes were added in Java SE 15. Class data support was
>     added in 16. `sun.misc.Unsafe::defineAnonymousClass` was
>     deprecated in JDK 15 and deprecated for terminally removal in JDK 16.
>     >>
>     >> I propose to remove `sun.misc.Unsafe::defineAnonymousClass`
>     from JDK 17:
>     >> CSR: https://bugs.openjdk.java.net/browse/JDK-8266760
>     <https://bugs.openjdk.java.net/browse/JDK-8266760>
>     >>
>     >> Comments?
>     >>
>     >> Mandy
>