Summary

The RegisterFinalizersAtInit option controls whether finalizers are registered after allocation or at return from the Object.<init> constructor. The default is to register at the end of Object.<init> and this has been the default for years.

Problem

Continuing to support the flag is counter to the increased Integrity push [0] and will be increasingly problematic when Project Valhalla merges in due to allowing larval objects to escape before they are frozen.

[0] https://openjdk.org/jeps/8305968

Solution

Deprecate the option in JDK22, obsolete in JDK23, and expire in JDK24.

Specification

diff --git a/src/hotspot/share/runtime/arguments.cpp b/src/hotspot/share/runtime/arguments.cpp
index dc1e15121b28..f6c1b0003e83 100644
--- a/src/hotspot/share/runtime/arguments.cpp
+++ b/src/hotspot/share/runtime/arguments.cpp
@@ -509,6 +509,7 @@ static SpecialFlag const special_jvm_flags[] = {
   { "DynamicDumpSharedSpaces",      JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::undefined() },
   { "RequireSharedSpaces",          JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::undefined() },
   { "UseSharedSpaces",              JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::undefined() },
+  { "RegisterFinalizersAtInit",     JDK_Version::jdk(22), JDK_Version::jdk(23), JDK_Version::jdk(24) },
 
   // --- Deprecated alias flags (see also aliased_jvm_flags) - sorted by obsolete_in then expired_in:
   { "DefaultMaxRAMFraction",        JDK_Version::jdk(8),  JDK_Version::undefined(), JDK_Version::undefined() },
diff --git a/src/hotspot/share/runtime/globals.hpp b/src/hotspot/share/runtime/globals.hpp
index 4ae156a773ea..f3c1ceab3d7f 100644
--- a/src/hotspot/share/runtime/globals.hpp
+++ b/src/hotspot/share/runtime/globals.hpp
@@ -667,8 +667,8 @@ const int ObjectAlignmentInBytes = 8;
           "Print JVM warnings to output stream")                            \
                                                                             \
   product(bool, RegisterFinalizersAtInit, true,                             \
-          "Register finalizable objects at end of Object.<init> or "        \
-          "after allocation")                                               \
+          "(Deprecated) Register finalizable objects at end of "            \
+          "Object.<init> or after allocation")                              \
                                                                             \
   develop(bool, RegisterReferences, true,                                   \
           "Tell whether the VM should register soft/weak/final/phantom "    \