added hook for object reachability notifications

Author: dougxc

sdk/src/org.graalvm.nativeimage/snapshot.sigtest

@@ -1051,6 +1051,7 @@ CLSS public abstract interface static org.graalvm.nativeimage.hosted.Feature$Dur
  outer org.graalvm.nativeimage.hosted.Feature
 intf org.graalvm.nativeimage.hosted.Feature$FeatureAccess
 meth public abstract void registerObjectReplacer(java.util.function.Function<java.lang.Object,java.lang.Object>)
+meth public abstract void registerObjectReachabilityHandler(java.util.function.Consumer<T>,java.lang.Class<T>)
 
 CLSS public abstract interface static org.graalvm.nativeimage.hosted.Feature$FeatureAccess
  outer org.graalvm.nativeimage.hosted.Feature

sdk/src/org.graalvm.nativeimage/src/org/graalvm/nativeimage/hosted/Feature.java

@@ -191,6 +191,14 @@ interface DuringSetupAccess extends FeatureAccess {
          * @since 19.0
          */
         void registerObjectReplacer(Function<Object, Object> replacer);
+
+        /**
+         * Register a callback that is executed when an object of type {@code clazz}, or any of its
+         * subtypes, is marked as reachable during heap scanning.
+         *
+         * @since 24.2
+         */
+        <T> void registerObjectReachabilityHandler(Consumer<T> callback, Class<T> clazz);
     }
 
     /**

substratevm/CHANGELOG.md

@@ -3,6 +3,7 @@
 This changelog summarizes major changes to GraalVM Native Image.
 
 ## GraalVM for JDK 24 (Internal Version 24.2.0)
+* (GR-59717) Added `DuringSetupAccess.registerObjectReachabilityHandler` to allow registering a callback that is executed when an object of a specified type is marked as reachable during heap scanning.
 * (GR-55708) (Alibaba contribution) Support for running premain methods of Java agents at runtime as an experimental feature. At build time, `-H:PremainClasses` is used to set the premain classes.
 At runtime, premain runtime options are set along with main class' arguments in the format of `-XXpremain:[class]:[options]`.
 * (GR-54476): Issue a deprecation warning on first use of a legacy `graal.` prefix (see GR-49960 in [Compiler changelog](../compiler/CHANGELOG.md)).

substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalFeature.java

@@ -53,9 +53,7 @@
 import org.graalvm.nativeimage.hosted.RuntimeReflection;
 
 import com.oracle.graal.pointsto.BigBang;
-import com.oracle.graal.pointsto.ObjectScanner;
 import com.oracle.graal.pointsto.meta.AnalysisType;
-import com.oracle.graal.pointsto.meta.ObjectReachableCallback;
 import com.oracle.graal.pointsto.reports.CallTreePrinter;
 import com.oracle.svm.core.SubstrateTargetDescription;
 import com.oracle.svm.core.hub.ClassForNameSupport;
@@ -256,8 +254,8 @@ public void duringSetup(DuringSetupAccess access) {
         DuringSetupAccessImpl accessImpl = (DuringSetupAccessImpl) access;
         accessImpl.registerClassReachabilityListener(this::registerPhaseStatistics);
         optionCollector = new OptionCollector(LibGraalEntryPoints.vmOptionDescriptors);
-        accessImpl.registerObjectReachableCallback(OptionKey.class, optionCollector::doCallback);
-        accessImpl.registerObjectReachableCallback(loadClassOrFail(OptionKey.class.getName()), optionCollector::doCallback);
+        access.registerObjectReachabilityHandler(optionCollector::accept, OptionKey.class);
+        access.registerObjectReachabilityHandler(optionCollector::accept, loadClassOrFail(OptionKey.class.getName()));
         GetJNIConfig.register(loader);
     }
 
@@ -270,7 +268,7 @@ public void duringSetup(DuringSetupAccess access) {
      * compiler options are instances of {@link OptionKey} loaded by the
      * {@code HostedLibGraalClassLoader}.
      */
-    private class OptionCollector implements ObjectReachableCallback<Object> {
+    private class OptionCollector implements Consumer<Object> {
         private final Set<Object> options = Collections.newSetFromMap(new ConcurrentHashMap<>());
 
         /**
@@ -297,7 +295,7 @@ private class OptionCollector implements ObjectReachableCallback<Object> {
         }
 
         @Override
-        public void doCallback(DuringAnalysisAccess access, Object option, ObjectScanner.ScanReason reason) {
+        public void accept(Object option) {
             if (sealed) {
                 VMError.guarantee(options.contains(option), "All options must have been discovered during static analysis: %s", option);
             } else {

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/FeatureImpl.java

@@ -317,6 +317,12 @@ public <T> void registerObjectReachableCallback(Class<T> clazz, ObjectReachableC
             getMetaAccess().lookupJavaType(clazz).registerObjectReachableCallback(callback);
         }
 
+        @Override
+        public <T> void registerObjectReachabilityHandler(Consumer<T> callback, Class<T> clazz) {
+            ObjectReachableCallback<T> wrapper = (access, obj, reason) -> callback.accept(obj);
+            getMetaAccess().lookupJavaType(clazz).registerObjectReachableCallback(wrapper);
+        }
+
         public void registerSubstitutionProcessor(SubstitutionProcessor substitution) {
             getUniverse().registerFeatureSubstitution(substitution);
         }