Add the concept of a V8 extras exports object

Exposed to the extras as extrasExports (on the builtins object), on
which they can put things that should be accessible from C++. Exposed
to C++ through the V8 API as v8::Context::GetExtrasExportsObject().

Adding a test (in test-api.cc) required adding a simple extra,
test-extra.js, which we build into the standalone builds.

R=yangguo@chromium.org, jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1128113006

Cr-Commit-Position: refs/heads/master@{#28317}

build/standalone.gypi

@@ -100,6 +100,9 @@
     'msan%': '<(msan)',
     'tsan%': '<(tsan)',
 
+    # Add a simple extra solely for the purpose of the cctests
+    'v8_extra_library_files': ['../test/cctest/test-extra.js'],
+
     # .gyp files or targets should set v8_code to 1 if they build V8 specific
     # code, as opposed to external code.  This variable is used to control such
     # things as the set of warnings to enable, and whether warnings are treated

include/v8.h

@@ -6370,6 +6370,12 @@ class V8_EXPORT Context {
    */
   V8_INLINE Local<Value> GetEmbedderData(int index);
 
+  /**
+   * Gets the exports object used by V8 extras. Extra natives get a reference
+   * to this object and can use it to export functionality.
+   */
+  Local<Object> GetExtrasExportsObject();
+
   /**
    * Sets the embedder data with the given index, growing the data as
    * needed. Note that index 0 currently has a special meaning for Chrome's

src/api.cc

@@ -5492,6 +5492,14 @@ void Context::DetachGlobal() {
 }
 
 
+Local<v8::Object> Context::GetExtrasExportsObject() {
+  i::Handle<i::Context> context = Utils::OpenHandle(this);
+  i::Isolate* isolate = context->GetIsolate();
+  i::Handle<i::JSObject> exports(context->extras_exports_object(), isolate);
+  return Utils::ToLocal(exports);
+}
+
+
 void Context::AllowCodeGenerationFromStrings(bool allow) {
   i::Handle<i::Context> context = Utils::OpenHandle(this);
   i::Isolate* isolate = context->GetIsolate();

src/bootstrapper.cc

@@ -201,6 +201,7 @@ class Genesis BASE_EMBEDDED {
   void InitializeGlobal(Handle<GlobalObject> global_object,
                         Handle<JSFunction> empty_function);
   void InitializeExperimentalGlobal();
+  void InitializeExtrasExportsObject();
   // Installs the contents of the native .js files on the global objects.
   // Used for creating a context from scratch.
   void InstallNativeFunctions();
@@ -1441,6 +1442,20 @@ void Genesis::InitializeExperimentalGlobal() {
 }
 
 
+void Genesis::InitializeExtrasExportsObject() {
+  Handle<JSObject> exports =
+      factory()->NewJSObject(isolate()->object_function(), TENURED);
+
+  native_context()->set_extras_exports_object(*exports);
+
+  Handle<JSBuiltinsObject> builtins(native_context()->builtins());
+  Handle<String> exports_string =
+      factory()->InternalizeOneByteString(STATIC_CHAR_VECTOR("extrasExports"));
+  Runtime::SetObjectProperty(isolate(), builtins, exports_string, exports,
+                             STRICT).Assert();
+}
+
+
 bool Genesis::CompileBuiltin(Isolate* isolate, int index) {
   Vector<const char> name = Natives::GetScriptName(index);
   Handle<String> source_code =
@@ -2962,6 +2977,7 @@ Genesis::Genesis(Isolate* isolate,
   // them after they have already been deserialized would also fail.
   if (!isolate->serializer_enabled()) {
     InitializeExperimentalGlobal();
+    InitializeExtrasExportsObject();
     if (!InstallExperimentalNatives()) return;
     if (!InstallExtraNatives()) return;
   }

src/contexts.h

@@ -185,7 +185,8 @@ enum BindingFlags {
   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
   V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map)                             \
   V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)            \
-  V(SCRIPT_CONTEXT_TABLE_INDEX, ScriptContextTable, script_context_table)
+  V(SCRIPT_CONTEXT_TABLE_INDEX, ScriptContextTable, script_context_table)      \
+  V(EXTRAS_EXPORTS_OBJECT_INDEX, JSObject, extras_exports_object)
 
 
 // A table of all script contexts. Every loaded top-level script with top-level
@@ -422,6 +423,7 @@ class Context: public FixedArray {
     SCRIPT_CONTEXT_TABLE_INDEX,
     MAP_CACHE_INDEX,
     TO_LENGTH_FUN_INDEX,
+    EXTRAS_EXPORTS_OBJECT_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.

src/runtime/runtime-test.cc

@@ -364,6 +364,12 @@ RUNTIME_FUNCTION(Runtime_NativeScriptsCount) {
 }
 
 
+RUNTIME_FUNCTION(Runtime_NativeExtrasCount) {
+  DCHECK(args.length() == 0);
+  return Smi::FromInt(ExtraNatives::GetBuiltinsCount());
+}
+
+
 // Returns V8 version as a string.
 RUNTIME_FUNCTION(Runtime_GetV8Version) {
   HandleScope scope(isolate);

src/runtime/runtime.h

@@ -592,6 +592,7 @@ namespace internal {
   F(Abort, 1, 1)                              \
   F(AbortJS, 1, 1)                            \
   F(NativeScriptsCount, 0, 1)                 \
+  F(NativeExtrasCount, 0, 1)                  \
   F(GetV8Version, 0, 1)                       \
   F(DisassembleFunction, 1, 1)                \
   F(TraceEnter, 0, 1)                         \

test/cctest/test-api.cc

@@ -21029,3 +21029,21 @@ TEST(SealHandleScopeNested) {
     USE(obj);
   }
 }
+
+
+TEST(ExtrasExportsObject) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope handle_scope(isolate);
+  LocalContext env;
+
+  // standalone.gypi ensures we include the test-extra.js file, which should
+  // add the testExtraShouldReturnFive export
+  v8::Local<v8::Object> exports = env->GetExtrasExportsObject();
+
+  auto func =
+      exports->Get(v8_str("testExtraShouldReturnFive")).As<v8::Function>();
+  auto undefined = v8::Undefined(isolate);
+  auto result = func->Call(undefined, 0, {}).As<v8::Number>();
+
+  CHECK(result->Value() == 5.0);
+}

test/cctest/test-extra.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+(function () {
+    'use strict';
+
+    extrasExports.testExtraShouldReturnFive = function () {
+        return 5;
+    };
+})();

test/mjsunit/debug-script.js

@@ -66,7 +66,7 @@ for (i = 0; i < scripts.length; i++) {
 }
 
 // This has to be updated if the number of native scripts change.
-assertEquals(%NativeScriptsCount(), named_native_count);
+assertEquals(%NativeScriptsCount() + %NativeExtrasCount(), named_native_count);
 // Only the 'gc' extension is loaded.
 assertEquals(1, extension_count);
 // This script and mjsunit.js has been loaded.  If using d8, d8 loads