8369451: Debug agent support for USE_ITERATE_THROUGH_HEAP is broken and should be removed

src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 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
@@ -890,8 +890,6 @@ printUsage(void)
  " everything = 0xfff"));
 
  TTY_MESSAGE((
- "debugflags=flags debug flags (bitmask) none\n"
- " USE_ITERATE_THROUGH_HEAP 0x01\n"
  "\n"
  "Environment Variables\n"
  "---------------------\n"
@@ -1192,13 +1190,6 @@ parseOptions(char *options)
  }
  /*LINTED*/
  logflags = (unsigned)strtol(current, NULL, 0);
- } else if (strcmp(buf, "debugflags") == 0) {
- /*LINTED*/
- if (!get_tok(&str, current, (int)(end - current), ',')) {
- goto syntax_error;
- }
- /*LINTED*/
- gdata->debugflags = (unsigned)strtol(current, NULL, 0);
  } else if ( strcmp(buf, "suspend")==0 ) {
  if ( !get_boolean(&str, &suspendOnInit) ) {
  goto syntax_error;

src/jdk.jdwp.agent/share/native/libjdwp/util.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 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
@@ -2730,10 +2730,6 @@ typedef struct ClassCountData {
  jvmtiError error;
 } ClassCountData;
 
-/* Two different cbObjectCounter's, one for FollowReferences, one for
- * IterateThroughHeap. Pick a card, any card.
- */
-
 /* Callback for object count heap traversal (heap_reference_callback) */
 static jint JNICALL
 cbObjectCounterFromRef(jvmtiHeapReferenceKind reference_kind,
@@ -2795,38 +2791,6 @@ cbObjectCounterFromRef(jvmtiHeapReferenceKind reference_kind,
  return JVMTI_VISIT_OBJECTS;
 }
 
-/* Callback for instance count heap traversal (heap_iteration_callback) */
-static jint JNICALL
-cbObjectCounter(jlong class_tag, jlong size, jlong* tag_ptr, jint length,
- void* user_data)
-{
- ClassCountData *data;
- int index;
-
- /* Check data structure */
- data = (ClassCountData*)user_data;
- if (data == NULL) {
- return JVMTI_VISIT_ABORT;
- }
-
- /* Classes with no tag should be filtered out. */
- if ( class_tag == (jlong)0 ) {
- data->error = AGENT_ERROR_INTERNAL;
- return JVMTI_VISIT_ABORT;
- }
-
- /* Class tag is actually an index into data arrays */
- index = CLASSTAG2INDEX(class_tag);
- if (index < 0 || index >= data->classCount) {
- data->error = AGENT_ERROR_ILLEGAL_ARGUMENT;
- return JVMTI_VISIT_ABORT;
- }
-
- /* Bump instance count on this class */
- data->counts[index]++;
- return JVMTI_VISIT_OBJECTS;
-}
-
 /* Get instance counts for a set of classes */
 jvmtiError
 classInstanceCounts(jint classCount, jclass *classes, jlong *counts)
@@ -2879,53 +2843,27 @@ classInstanceCounts(jint classCount, jclass *classes, jlong *counts)
  /* Clear out callbacks structure */
  (void)memset(&heap_callbacks,0,sizeof(heap_callbacks));
 
- /* Check debug flags to see how to do this. */
- if ( (gdata->debugflags & USE_ITERATE_THROUGH_HEAP) == 0 ) {
-
- /* Using FollowReferences only gives us live objects, but we
- * need to tag the objects to avoid counting them twice since
- * the callback is per reference.
- * The jclass objects have been tagged with their index in the
- * supplied list, and that tag may flip to negative if it
- * is also an object of interest.
- * All other objects being counted that weren't in the
- * supplied classes list will have a negative classCount
- * tag value. So all objects counted will have negative tags.
- * If the absolute tag value is an index in the supplied
- * list, then it's one of the supplied classes.
- */
- data.negObjTag = -INDEX2CLASSTAG(classCount);
-
- /* Setup callbacks, only using object reference callback */
- heap_callbacks.heap_reference_callback = &cbObjectCounterFromRef;
-
- /* Follow references, no initiating object, tagged classes only */
- error = JVMTI_FUNC_PTR(jvmti,FollowReferences)
- (jvmti, JVMTI_HEAP_FILTER_CLASS_UNTAGGED,
- NULL, NULL, &heap_callbacks, &data);
-
- } else {
-
- /* Using IterateThroughHeap means that we will visit each object
- * once, so no special tag tricks here. Just simple counting.
- * However in this case the object might not be live, so we do
- * a GC beforehand to make sure we minimize this.
- */
-
- /* FIXUP: Need some kind of trigger here to avoid excessive GC's? */
- error = JVMTI_FUNC_PTR(jvmti,ForceGarbageCollection)(jvmti);
- if ( error != JVMTI_ERROR_NONE ) {
-
- /* Setup callbacks, just need object callback */
- heap_callbacks.heap_iteration_callback = &cbObjectCounter;
+ /* Using FollowReferences only gives us live objects, but we
+ * need to tag the objects to avoid counting them twice since
+ * the callback is per reference.
+ * The jclass objects have been tagged with their index in the
+ * supplied list, and that tag may flip to negative if it
+ * is also an object of interest.
+ * All other objects being counted that weren't in the
+ * supplied classes list will have a negative classCount
+ * tag value. So all objects counted will have negative tags.
+ * If the absolute tag value is an index in the supplied
+ * list, then it's one of the supplied classes.
+ */
+ data.negObjTag = -INDEX2CLASSTAG(classCount);
 
- /* Iterate through entire heap, tagged classes only */
- error = JVMTI_FUNC_PTR(jvmti,IterateThroughHeap)
- (jvmti, JVMTI_HEAP_FILTER_CLASS_UNTAGGED,
- NULL, &heap_callbacks, &data);
+ /* Setup callbacks, only using object reference callback */
+ heap_callbacks.heap_reference_callback = &cbObjectCounterFromRef;
 
- }
- }
+ /* Follow references, no initiating object, tagged classes only */
+ error = JVMTI_FUNC_PTR(jvmti,FollowReferences)
+ (jvmti, JVMTI_HEAP_FILTER_CLASS_UNTAGGED,
+ NULL, NULL, &heap_callbacks, &data);
 
  /* Use data error if needed */
  if ( error == JVMTI_ERROR_NONE ) {

src/jdk.jdwp.agent/share/native/libjdwp/util.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 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
@@ -92,12 +92,6 @@ typedef struct {
  jboolean quiet;
  jboolean jvmti_data_dump; /* If true, then support JVMTI DATA_DUMP_REQUEST events. */
 
- /* Debug flags (bit mask) */
- int debugflags;
-
- /* Possible debug flags */
- #define USE_ITERATE_THROUGH_HEAP 0X001
-
  char * options;
 
  jclass classClass;