Hmm, I think Proxy being hidden in stacktraces might be an advantage; the same happens for lambdas. The main advantage of hidden classes compared to an explicit class with classData is that it supports flexible unloading, which might be useful for Proxy. I still believe the flexible unloading advantage justifies the migration to hidden classes.
Chen On Thu, May 23, 2024 at 6:43 AM Remi Forax <fo...@univ-mlv.fr> wrote: > ----- Original Message ----- > > From: "Chen Liang" <li...@openjdk.org> > > To: "core-libs-dev" <core-libs-dev@openjdk.org>, "hotspot-dev" < > hotspot-...@openjdk.org>, kulla-...@openjdk.org > > Sent: Thursday, May 23, 2024 1:28:01 PM > > Subject: Re: RFR: 8242888: Convert dynamic proxy to hidden classes > > > On Thu, 23 May 2024 03:28:30 GMT, Chen Liang <li...@openjdk.org> wrote: > > > >> Please review this change that convert dynamic proxies implementations > to hidden > >> classes, intended to target JDK 24. > >> > >> Summary: > >> 1. Adds new implementation while preserving the old implementation > behind > >> `-Djdk.reflect.useLegacyProxyImpl=true` in case there are compatibility > issues. > >> 2. ClassLoader.defineClass0 takes a ClassLoader instance but discards > it in > >> native code; I updated native code to reuse that ClassLoader for Proxy > support. > >> 3. ProxyGenerator changes mainly involve using Class data to pass > Method list > >> (accessed in a single condy) and removal of obsolete setup code > generation. > >> > >> Testing: tier1 and tier2 have no related failures. > >> > >> Comment: Since #8278, Proxy has been converted to ClassFile API, and > >> infrastructure has changed; now, the migration to hidden classes is much > >> cleaner and has less impact, such as preserving ProtectionDomain and > dynamic > >> module without "anchor classes", and avoiding java.lang.invoke package. > > > > A CSR targeting 24 describing the compatibility concerns and behavioral > > differences is here, somehow not linked by skara: > > https://bugs.openjdk.org/browse/JDK-8332770 > > The incompatibilities were much greater in the previous iterations of > this > > issue, such as in dynamic modules, serialization, and in proxy class > protection > > domain. Now these aspects are addressed by this patch, the only real one > left > > is the change in stack trace. Feel free to raise other incompatibilities > you > > have discovered. > > I wonder if instead of using hidden classes, we should not use usual named > classes and add a new Lookup.defineClass() that takes a classData as > parameter. > This will solve the both the problem of the stacktrace and the problem of > the roundtrip proxyClass != Class.forName(proxyClass.getName()). > > Rémi > > > > > ------------- > > > > PR Comment: > https://git.openjdk.org/jdk/pull/19356#issuecomment-2126869679 >
