Add internal properties [[ArrayBufferData]] and [[ArrayBufferByteLength]]

New internal properties expose the byte length of an ArrayBuffer as well
as the pointer to the backing store, which will serve as a unique ID
to show when SharedArrayBuffers in different workers are the same buffer.

Bug: chromium:1163800
Change-Id: I49930765cb38f75ba5c6cee5a0a6827f4fec42d5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2618242
Commit-Queue: Eric Leese <leese@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72000}

src/runtime/runtime-debug.cc

@@ -324,7 +324,8 @@ MaybeHandle<JSArray> Runtime::GetInternalProperties(Isolate* isolate,
         kExternalInt16Array,
         kExternalInt32Array,
     };
-    Handle<FixedArray> result = factory->NewFixedArray(arraysize(kTypes) * 2);
+    Handle<FixedArray> result =
+        factory->NewFixedArray((2 + arraysize(kTypes)) * 2);
     int index = 0;
     for (auto type : kTypes) {
       switch (type) {
@@ -346,6 +347,23 @@ MaybeHandle<JSArray> Runtime::GetInternalProperties(Isolate* isolate,
           UNREACHABLE();
       }
     }
+    Handle<String> byte_length_str =
+        factory->NewStringFromAsciiChecked("[[ArrayBufferByteLength]]");
+    result->set(index++, *byte_length_str);
+    Handle<Object> byte_length_obj = factory->NewNumberFromSize(byte_length);
+    result->set(index++, *byte_length_obj);
+    Handle<String> buffer_data_str =
+        factory->NewStringFromAsciiChecked("[[ArrayBufferData]]");
+    result->set(index++, *buffer_data_str);
+    // Use the backing store pointer as a unique ID
+    EmbeddedVector<char, 32> buffer_data_vec;
+    int len =
+        SNPrintF(buffer_data_vec, V8PRIxPTR_FMT,
+                 reinterpret_cast<Address>(js_array_buffer->backing_store()));
+    Handle<String> buffer_id =
+        factory->InternalizeUtf8String(buffer_data_vec.SubVector(0, len));
+    result->set(index++, *buffer_id);
+
     return factory->NewJSArrayWithElements(result, PACKED_ELEMENTS, index);
   } else if (object->IsWasmModuleObject()) {
     auto module_object = Handle<WasmModuleObject>::cast(object);

test/inspector/debugger/get-properties-paused-expected.txt

@@ -56,5 +56,7 @@ Running test: testArrayBuffer
 Running test: testArrayBufferWithBrokenUintCtor
   __proto__ own object undefined
 Internal properties
+  [[ArrayBufferByteLength]] number 7
+  [[ArrayBufferData]] string 0x...
   [[Int8Array]] object undefined
   [[Uint8Array]] object undefined

test/inspector/debugger/get-properties-paused.js

@@ -98,7 +98,11 @@ let { Protocol } = InspectorTest.start('Checks Runtime.getProperties method whil
       for (var i = 0; i < internalPropertyArray.length; i++) {
         var p = internalPropertyArray[i];
         var v = p.value;
-        InspectorTest.log(`  ${p.name} ${v.type} ${v.value}`);
+        if (p.name === "[[ArrayBufferData]]")
+          // Hex value for pointer is non-deterministic
+          InspectorTest.log(`  ${p.name} ${v.type} ${v.value.substr(0, 2)}...`);
+        else
+          InspectorTest.log(`  ${p.name} ${v.type} ${v.value}`);
       }
     }
 

test/inspector/runtime/get-properties-expected.txt

@@ -102,6 +102,8 @@ Running test: testArrayBuffer
   0 own number 16843009
   1 own number 16843009
   __proto__ own object undefined
+[[ArrayBufferByteLength]]
+[[ArrayBufferData]]
 
 Running test: testDetachedArrayBuffer
 [[IsDetached]] true
@@ -109,5 +111,7 @@ Running test: testDetachedArrayBuffer
 Running test: testArrayBufferWithBrokenUintCtor
   __proto__ own object undefined
 Internal properties
+  [[ArrayBufferByteLength]] number 7
+  [[ArrayBufferData]] string 0x...
   [[Int8Array]] object undefined
   [[Uint8Array]] object undefined

test/inspector/runtime/get-properties.js

@@ -52,7 +52,8 @@ InspectorTest.runAsyncTestSuite([
     }
     for (let prop of props.result.internalProperties) {
       InspectorTest.log(prop.name);
-      await logGetPropertiesResult(prop.value.objectId);
+      if (prop.value.objectId)
+        await logGetPropertiesResult(prop.value.objectId);
     }
   },
 
@@ -112,7 +113,7 @@ async function logGetPropertiesResult(objectId, flags = { ownProperties: true })
     var v = p.value;
     var own = p.isOwn ? "own" : "inherited";
     if (v)
-      InspectorTest.log("  " + p.name + " " + own + " " + v.type + " " + v.value);
+      InspectorTest.log(`  ${p.name} ${own} ${v.type} ${v.value}`);
     else
       InspectorTest.log("  " + p.name + " " + own + " no value" +
         (hasGetterSetter(p, "get") ? ", getter" : "") + (hasGetterSetter(p, "set") ? ", setter" : ""));
@@ -125,7 +126,11 @@ async function logGetPropertiesResult(objectId, flags = { ownProperties: true })
     for (var i = 0; i < array.length; i++) {
       var p = array[i];
       var v = p.value;
-      InspectorTest.log('  ' + p.name + ' ' + v.type + ' ' + v.value);
+      if (p.name == "[[ArrayBufferData]]")
+        // Hex value for pointer is non-deterministic
+        InspectorTest.log(`  ${p.name} ${v.type} ${v.value.substr(0, 2)}...`);
+      else
+        InspectorTest.log(`  ${p.name} ${v.type} ${v.value}`);
     }
   }