Make sure that when a SupportsUserData is destroyed, objects destroyed transitively see it as empty.

BUG=358707

Review URL: https://codereview.chromium.org/298023008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273568 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 46 insertions, 0 deletions

diff --git a/base/BUILD.gn b/base/BUILD.gn
index b4faecf..7a19b7a 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1173,6 +1173,7 @@ test("base_unittests") {
     "strings/sys_string_conversions_unittest.cc",
     "strings/utf_offset_string_conversions_unittest.cc",
     "strings/utf_string_conversions_unittest.cc",
+    "supports_user_data_unittest.cc",
     "sync_socket_unittest.cc",
     "synchronization/cancellation_flag_unittest.cc",
     "synchronization/condition_variable_unittest.cc",
diff --git a/base/base.gyp b/base/base.gyp
index df8c21b..710c229 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -578,6 +578,7 @@
         'strings/sys_string_conversions_unittest.cc',
         'strings/utf_offset_string_conversions_unittest.cc',
         'strings/utf_string_conversions_unittest.cc',
+        'supports_user_data_unittest.cc',
         'sync_socket_unittest.cc',
         'synchronization/cancellation_flag_unittest.cc',
         'synchronization/condition_variable_unittest.cc',
diff --git a/base/supports_user_data.cc b/base/supports_user_data.cc
index 2a0263e..9689014 100644
--- a/base/supports_user_data.cc
+++ b/base/supports_user_data.cc
@@ -35,6 +35,11 @@ void SupportsUserData::DetachUserDataThread() {
 
 SupportsUserData::~SupportsUserData() {
   DCHECK(thread_checker_.CalledOnValidThread() || user_data_.empty());
+  DataMap local_user_data;
+  user_data_.swap(local_user_data);
+  // Now this->user_data_ is empty, and any destructors called transitively from
+  // the destruction of |local_user_data| will see it that way instead of
+  // examining a being-destroyed object.
 }
 
 }  // namespace base
diff --git a/base/supports_user_data_unittest.cc b/base/supports_user_data_unittest.cc
new file mode 100644
index 0000000..f6afc37
--- /dev/null
+++ b/base/supports_user_data_unittest.cc
@@ -0,0 +1,39 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/supports_user_data.h"
+
+#include <vector>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+struct TestSupportsUserData : public SupportsUserData {};
+
+struct UsesItself : public SupportsUserData::Data {
+  UsesItself(SupportsUserData* supports_user_data, const void* key)
+      : supports_user_data_(supports_user_data),
+        key_(key) {
+  }
+
+  virtual ~UsesItself() {
+    EXPECT_EQ(NULL, supports_user_data_->GetUserData(key_));
+  }
+
+  SupportsUserData* supports_user_data_;
+  const void* key_;
+};
+
+TEST(SupportsUserDataTest, ClearWorksRecursively) {
+  TestSupportsUserData supports_user_data;
+  char key = 0;
+  supports_user_data.SetUserData(&key,
+                                 new UsesItself(&supports_user_data, &key));
+  // Destruction of supports_user_data runs the actual test.
+}
+
+}  // namespace
+}  // namespace base