From a21e90eb61f8010fe669d43f625532be007f6025 Mon Sep 17 00:00:00 2001
From: Polina Cherkasova <polinach@google.com>
Date: Tue, 11 Jul 2023 12:29:17 -0700
Subject: [PATCH] Protect from identityHashCode equal to 0. (#90)

---
 doc/TROUBLESHOOT.md                           |  5 +++--
 pkgs/leak_tracker/CHANGELOG.md                |  4 ++++
 .../src/leak_tracking/_object_tracker.dart    |  1 +
 .../lib/src/leak_tracking/orchestration.dart  |  3 +++
 .../retaining_path/_retaining_path.dart       | 20 ++++++++++++++++++-
 pkgs/leak_tracker/pubspec.yaml                |  2 +-
 6 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/doc/TROUBLESHOOT.md b/doc/TROUBLESHOOT.md
index e7eb008f..268a11cd 100644
--- a/doc/TROUBLESHOOT.md
+++ b/doc/TROUBLESHOOT.md
@@ -82,8 +82,9 @@ if (ref.target == null) {
 ```
 
 IMPORTANT: this code will not work in release mode, so
-you need to run it with flag `--debug` or `--profile`, or,
-if it is test, by clicking `Debug` near your test name in IDE.
+you need to run it with flag `--debug` or `--profile`
+([not available](https://github.com/flutter/flutter/issues/127331) for Flutter tests),
+or, if it is a test, by clicking `Debug` near the test name in IDE.
 
 ## Known complicated cases
 
diff --git a/pkgs/leak_tracker/CHANGELOG.md b/pkgs/leak_tracker/CHANGELOG.md
index aa4d7e8f..429d66cf 100644
--- a/pkgs/leak_tracker/CHANGELOG.md
+++ b/pkgs/leak_tracker/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 7.0.7
+
+* Protect from identityHashCode equal to 0.
+
 # 7.0.6
 
 * Add helpers for troubleshooting.
diff --git a/pkgs/leak_tracker/lib/src/leak_tracking/_object_tracker.dart b/pkgs/leak_tracker/lib/src/leak_tracking/_object_tracker.dart
index 89b36487..7a2242f8 100644
--- a/pkgs/leak_tracker/lib/src/leak_tracking/_object_tracker.dart
+++ b/pkgs/leak_tracker/lib/src/leak_tracking/_object_tracker.dart
@@ -54,6 +54,7 @@ class ObjectTracker implements LeakProvider {
   }) {
     throwIfDisposed();
     final code = _coder(object);
+    assert(code > 0);
     if (_checkForDuplicate(code)) return;
 
     _finalizer.attach(object, code);
diff --git a/pkgs/leak_tracker/lib/src/leak_tracking/orchestration.dart b/pkgs/leak_tracker/lib/src/leak_tracking/orchestration.dart
index 37783ba1..2ee24017 100644
--- a/pkgs/leak_tracker/lib/src/leak_tracking/orchestration.dart
+++ b/pkgs/leak_tracker/lib/src/leak_tracking/orchestration.dart
@@ -168,6 +168,9 @@ Future<void> forceGC({
 /// If the object is garbage collected or not retained, returns null.
 ///
 /// Does not work in web and in release mode.
+///
+/// Also does not work for objects that are not returned by getInstances.
+/// https://github.com/dart-lang/sdk/blob/3e80d29fd6fec56187d651ce22ea81f1e8732214/runtime/vm/object_graph.cc#L1803
 Future<String?> formattedRetainingPath(WeakReference ref) async {
   if (ref.target == null) return null;
   final path = await obtainRetainingPath(
diff --git a/pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_retaining_path.dart b/pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_retaining_path.dart
index 48777478..a649a7f5 100644
--- a/pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_retaining_path.dart
+++ b/pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_retaining_path.dart
@@ -9,7 +9,13 @@ import 'package:vm_service/vm_service.dart';
 
 import '_connection.dart';
 
+/// Obtains retainig path for an object.
+///
+/// Does not work for objects that have [identityHashCode] equal to 0.
+/// https://github.com/dart-lang/sdk/blob/3e80d29fd6fec56187d651ce22ea81f1e8732214/runtime/vm/object_graph.cc#L1803
 Future<RetainingPath?> obtainRetainingPath(Type type, int code) async {
+  assert(code > 0);
+
   final connection = await connect();
 
   final fp = _ObjectFingerprint(type, code);
@@ -26,7 +32,7 @@ Future<RetainingPath?> obtainRetainingPath(Type type, int code) async {
 }
 
 class _ObjectFingerprint {
-  _ObjectFingerprint(this.type, this.code);
+  _ObjectFingerprint(this.type, this.code) : assert(code > 0);
 
   final Type type;
   final int code;
@@ -39,6 +45,11 @@ class _ObjectFingerprint {
   }
 }
 
+/// Finds and object in an isolate.
+///
+/// This method will NOT find objects, that have [identityHashCode] equal to 0
+/// in result of `getInstances`.
+/// https://github.com/dart-lang/sdk/blob/3e80d29fd6fec56187d651ce22ea81f1e8732214/runtime/vm/object_graph.cc#L1803
 Future<_ItemInIsolate?> _objectInIsolate(
   Connection connection,
   _ObjectFingerprint object,
@@ -58,6 +69,9 @@ Future<_ItemInIsolate?> _objectInIsolate(
             .instances ??
         <ObjRef>[];
 
+    if (instances.isEmpty) continue;
+    assert(_refIsIdentifiable(instances.first));
+
     final result = instances.firstWhereOrNull(
       (objRef) =>
           objRef is InstanceRef && objRef.identityHashCode == object.code,
@@ -73,6 +87,10 @@ Future<_ItemInIsolate?> _objectInIsolate(
   return null;
 }
 
+bool _refIsIdentifiable(ObjRef ref) {
+  return ref is InstanceRef && (ref.identityHashCode ?? 0) > 0;
+}
+
 /// Represents an item in an isolate.
 ///
 /// It can be class or object.
diff --git a/pkgs/leak_tracker/pubspec.yaml b/pkgs/leak_tracker/pubspec.yaml
index 15f975f3..cd71ad5e 100644
--- a/pkgs/leak_tracker/pubspec.yaml
+++ b/pkgs/leak_tracker/pubspec.yaml
@@ -1,5 +1,5 @@
 name: leak_tracker
-version: 7.0.6
+version: 7.0.7
 description: A framework for memory leak tracking for Dart and Flutter applications.
 repository: https://github.com/dart-lang/leak_tracker/tree/main/pkgs/leak_tracker