8368799: [lworld] Heapwalking functions may report array classes several times

test/hotspot/jtreg/serviceability/jvmti/valhalla/HeapwalkDupClasses/HeapwalkDupClasses.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8368799
+ * @summary Verify heapwalking API does not report array classes several times.
+ * @requires vm.jvmti
+ * @modules java.base/jdk.internal.vm.annotation java.base/jdk.internal.value
+ * @enablePreview
+ * @run main/othervm/native -agentlib:HeapwalkDupClasses HeapwalkDupClasses
+ */
+
+import java.lang.ref.Reference;
+import jdk.internal.value.ValueClass;
+import jdk.internal.vm.annotation.NullRestricted;
+import jdk.internal.vm.annotation.Strict;
+
+public class HeapwalkDupClasses {
+
+    static native int tagWithFollowReferences(long tag);
+    static native int tagWithIterateOverReachableObjects(long tag);
+    static native Object[] getObjectsWithTags(long tag);
+
+    public static void main(String[] args) throws Exception {
+        System.loadLibrary("HeapwalkDupClasses");
+
+        Integer instance = new Integer(0);
+        Object[] testObjects = new Object[] {
+            new Integer[5],
+            ValueClass.newNullableAtomicArray(Integer.class, 5),
+            ValueClass.newNullRestrictedNonAtomicArray(Integer.class, 5, instance)
+        };
+
+        for (long tag = 1; tag <= 2; tag++) {
+            int taggedClasses;
+            if (tag == 1) {
+                System.out.println("FollowReferences");
+                taggedClasses = tagWithFollowReferences(tag);
+            } else {
+                System.out.println("IterateOverReachableObjects");
+                taggedClasses = tagWithIterateOverReachableObjects(tag);
+            }
+            System.out.println("Tagged " + taggedClasses + " classes");
+
+            Object[] taggedObjects = getObjectsWithTags(tag);
+            System.out.println("Tagged objects (total " + taggedObjects.length + "):");
+
+            int duplicates = 0;
+            boolean foundTestObjectClass[] = new boolean[testObjects.length];
+
+            for (int i = 0; i < taggedObjects.length; i++) {
+                System.out.println("[" + i + "] " + taggedObjects[i]);
+                for (int j = 0; j < i; j++) {
+                    if (taggedObjects[i].equals(taggedObjects[j])) {
+                        duplicates++;
+                        System.out.println("  ERROR: duplicate (" + j + ")");
+                    }
+                }
+                for (int j = 0; j < testObjects.length; j++) {
+                    if (taggedObjects[i].equals(testObjects[j].getClass())) {
+                        foundTestObjectClass[j] = true;
+                        System.out.println("  FOUND expected array class");
+                    }
+                }
+            }
+            if (duplicates != 0) {
+            throw new RuntimeException("Found " + duplicates + " duplicate classes");
+            }
+            for (int i = 0; i < foundTestObjectClass.length; i++) {
+                if (!foundTestObjectClass[i]) {
+                    throw new RuntimeException("Expected class not found: " + testObjects[i].getClass());
+                }
+            }
+        }
+    }
+}

test/hotspot/jtreg/serviceability/jvmti/valhalla/HeapwalkDupClasses/libHeapwalkDupClasses.cpp

@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include <jvmti.h>
+#include "jvmti_common.hpp"
+
+static jvmtiEnv *jvmti = nullptr;
+struct CallbackData {
+  jlong tag;
+  jint counter;
+
+  CallbackData(jlong tag): tag(tag), counter(0) {}
+};
+
+static jint JNICALL
+heap_reference_callback(jvmtiHeapReferenceKind reference_kind,
+                        const jvmtiHeapReferenceInfo* reference_info,
+                        jlong class_tag,
+                        jlong referrer_class_tag,
+                        jlong size,
+                        jlong* tag_ptr,
+                        jlong* referrer_tag_ptr,
+                        jint length,
+                        void* user_data) {
+  if (reference_kind == JVMTI_HEAP_REFERENCE_SYSTEM_CLASS) {
+    CallbackData* data = (CallbackData*)user_data;
+	data->counter++;
+    *tag_ptr = data->tag;
+  }
+  return JVMTI_VISIT_OBJECTS;
+}
+
+extern "C" JNIEXPORT jint JNICALL
+Java_HeapwalkDupClasses_tagWithFollowReferences(JNIEnv* jni, jclass clazz, jlong tag) {
+  jvmtiHeapCallbacks callbacks = {};
+  callbacks.heap_reference_callback = heap_reference_callback;
+
+  CallbackData data(tag);
+
+  jvmtiError err = jvmti->FollowReferences(0 /* filter nothing */,
+                                           nullptr /* no class filter */,
+                                           nullptr /* no initial object, follow roots */,
+                                           &callbacks,
+                                           &data);
+  check_jvmti_error(err, "FollowReferences failed");
+
+  return data.counter;
+}
+
+static jvmtiIterationControl JNICALL
+heap_root_callback(jvmtiHeapRootKind root_kind,
+                   jlong class_tag,
+                   jlong size,
+                   jlong* tag_ptr,
+                   void* user_data) {
+  if (root_kind == JVMTI_HEAP_ROOT_SYSTEM_CLASS) {
+    CallbackData* data = (CallbackData*)user_data;
+    data->counter++;
+    *tag_ptr = data->tag;
+  }
+  return JVMTI_ITERATION_CONTINUE;
+}
+
+extern "C" JNIEXPORT jint JNICALL
+Java_HeapwalkDupClasses_tagWithIterateOverReachableObjects(JNIEnv* jni, jclass clazz, jlong tag) {
+  CallbackData data(tag);
+  jvmtiError err = jvmti->IterateOverReachableObjects(heap_root_callback,
+                                                      nullptr,
+                                                      nullptr,
+                                                      &data);
+  check_jvmti_error(err, "IterateOverReachableObjects failed");
+
+  return data.counter;
+}
+
+extern "C" JNIEXPORT jobjectArray JNICALL
+Java_HeapwalkDupClasses_getObjectsWithTags(JNIEnv* jni, jclass clazz, jlong tag) {
+  jlong tags[1] = {tag};
+
+  jint count = 0;
+  jobject* objects = nullptr;
+
+  jvmtiError err = jvmti->GetObjectsWithTags(1, tags,
+                                  &count, &objects, nullptr);
+  check_jvmti_error(err, "GetObjectsWithTags failed");
+
+  jclass object_klass = jni->FindClass("java/lang/Object");
+  jobjectArray array = jni->NewObjectArray(count, object_klass, nullptr);
+
+  for (jint i = 0; i < count; i++) {
+    jni->SetObjectArrayElement(array, i, objects[i]);
+  }
+
+  deallocate(jvmti, jni, objects);
+
+  return array;
+}
+
+extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *vm, char *options, void *reserved) {
+  if (vm->GetEnv(reinterpret_cast<void**>(&jvmti), JVMTI_VERSION) != JNI_OK || !jvmti) {
+    LOG("Could not initialize JVMTI\n");
+    abort();
+  }
+  jvmtiCapabilities capabilities;
+  memset(&capabilities, 0, sizeof(capabilities));
+  capabilities.can_tag_objects = 1;
+  check_jvmti_error(jvmti->AddCapabilities(&capabilities), "adding capabilities");
+  return JVMTI_ERROR_NONE;
+}