From a5244d3a392d68e86e88b960c5b15c3c69f04d31 Mon Sep 17 00:00:00 2001
From: Fedor Indutny <fedor@indutny.com>
Date: Sat, 11 Apr 2015 16:02:22 +0200
Subject: [PATCH] deps: backport 1f8555 from v8's upstream

Original commit message:

    api: introduce SealHandleScope

    When debugging Handle leaks in io.js we found it very convenient to be
    able to Seal some specific (root in our case) scope to prevent Handle
    allocations in it, and easily find leakage.

    R=yangguo
    BUG=

    Review URL: https://codereview.chromium.org/1079713002

    Cr-Commit-Position: refs/heads/master@{#27766}

Should help us identify and fix Handle leaks in core and user-space code.

NOTE: Works only in Debug build now, but is still better than nothing.

PR-URL: https://github.com/iojs/io.js/pull/1395
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
---
 deps/v8/include/v8.h              | 18 +++++++++++++++++
 deps/v8/src/api.cc                | 21 ++++++++++++++++++++
 deps/v8/src/api.h                 |  5 +----
 deps/v8/test/cctest/cctest.status |  1 +
 deps/v8/test/cctest/test-api.cc   | 32 +++++++++++++++++++++++++++++++
 5 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/deps/v8/include/v8.h b/deps/v8/include/v8.h
index 32730ebc5f13..218e919a1677 100644
--- a/deps/v8/include/v8.h
+++ b/deps/v8/include/v8.h
@@ -1006,6 +1006,24 @@ class ScriptOrigin {
   Handle<Integer> script_id_;
 };
 
+class V8_EXPORT SealHandleScope {
+ public:
+  SealHandleScope(Isolate* isolate);
+  ~SealHandleScope();
+
+ private:
+  // Make it hard to create heap-allocated or illegal handle scopes by
+  // disallowing certain operations.
+  SealHandleScope(const SealHandleScope&);
+  void operator=(const SealHandleScope&);
+  void* operator new(size_t size);
+  void operator delete(void*, size_t);
+
+  internal::Isolate* isolate_;
+  int prev_level_;
+  internal::Object** prev_limit_;
+};
+
 
 /**
  * A compiled JavaScript script, not yet tied to a Context.
diff --git a/deps/v8/src/api.cc b/deps/v8/src/api.cc
index 88d3c889b96c..c3f84534b4b5 100644
--- a/deps/v8/src/api.cc
+++ b/deps/v8/src/api.cc
@@ -515,6 +515,27 @@ i::Object** EscapableHandleScope::Escape(i::Object** escape_value) {
 }
 
 
+SealHandleScope::SealHandleScope(Isolate* isolate) {
+  i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
+
+  isolate_ = internal_isolate;
+  i::HandleScopeData* current = internal_isolate->handle_scope_data();
+  prev_limit_ = current->limit;
+  current->limit = current->next;
+  prev_level_ = current->level;
+  current->level = 0;
+}
+
+
+SealHandleScope::~SealHandleScope() {
+  i::HandleScopeData* current = isolate_->handle_scope_data();
+  DCHECK_EQ(0, current->level);
+  current->level = prev_level_;
+  DCHECK_EQ(current->next, current->limit);
+  current->limit = prev_limit_;
+}
+
+
 void Context::Enter() {
   i::Handle<i::Context> env = Utils::OpenHandle(this);
   i::Isolate* isolate = env->GetIsolate();
diff --git a/deps/v8/src/api.h b/deps/v8/src/api.h
index 1d2a8c8e8282..62f9f1e0b351 100644
--- a/deps/v8/src/api.h
+++ b/deps/v8/src/api.h
@@ -650,7 +650,7 @@ void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
   while (!blocks_.is_empty()) {
     internal::Object** block_start = blocks_.last();
     internal::Object** block_limit = block_start + kHandleBlockSize;
-#ifdef DEBUG
+
     // SealHandleScope may make the prev_limit to point inside the block.
     if (block_start <= prev_limit && prev_limit <= block_limit) {
 #ifdef ENABLE_HANDLE_ZAPPING
@@ -658,9 +658,6 @@ void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
 #endif
       break;
     }
-#else
-    if (prev_limit == block_limit) break;
-#endif
 
     blocks_.RemoveLast();
 #ifdef ENABLE_HANDLE_ZAPPING
diff --git a/deps/v8/test/cctest/cctest.status b/deps/v8/test/cctest/cctest.status
index cc5414da2736..95fb839aa623 100644
--- a/deps/v8/test/cctest/cctest.status
+++ b/deps/v8/test/cctest/cctest.status
@@ -40,6 +40,7 @@
   # they don't fail then test.py has failed.
   'test-serialize/TestThatAlwaysFails': [FAIL],
   'test-serialize/DependentTestThatAlwaysFails': [FAIL],
+  'test-api/SealHandleScope': [FAIL],
 
   # This test always fails.  It tests that LiveEdit causes abort when turned off.
   'test-debug/LiveEditDisabled': [FAIL],
diff --git a/deps/v8/test/cctest/test-api.cc b/deps/v8/test/cctest/test-api.cc
index 06cf5532e244..17de186b9c4c 100644
--- a/deps/v8/test/cctest/test-api.cc
+++ b/deps/v8/test/cctest/test-api.cc
@@ -21895,6 +21895,38 @@ void CallCompletedCallbackException() {
 }
 
 
+TEST(SealHandleScope) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope handle_scope(isolate);
+  LocalContext env;
+
+  v8::SealHandleScope seal(isolate);
+
+  // Should fail
+  v8::Local<v8::Object> obj = v8::Object::New(isolate);
+
+  USE(obj);
+}
+
+
+TEST(SealHandleScopeNested) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope handle_scope(isolate);
+  LocalContext env;
+
+  v8::SealHandleScope seal(isolate);
+
+  {
+    v8::HandleScope handle_scope(isolate);
+
+    // Should work
+    v8::Local<v8::Object> obj = v8::Object::New(isolate);
+
+    USE(obj);
+  }
+}
+
+
 TEST(CallCompletedCallbackOneException) {
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());