Bug 1303714 - Always Unwrap ArrayBuffer in TypedArray constructor. r=bholley

js/src/vm/TypedArrayObject.cpp

@@ -765,15 +765,6 @@ class TypedArrayObjectTemplate : public TypedArrayObject
     fromBufferWithProto(JSContext* cx, HandleObject bufobj, uint32_t byteOffset, int32_t lengthInt,
                         HandleObject proto)
     {
-        ESClass cls;
-        if (!GetBuiltinClass(cx, bufobj, &cls))
-            return nullptr;
-        if (cls != ESClass::ArrayBuffer && cls != ESClass::SharedArrayBuffer) {
-            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_BAD_ARGS);
-            return nullptr;
-        }
-
-        MOZ_ASSERT(IsArrayBuffer(bufobj) || IsSharedArrayBuffer(bufobj) || bufobj->is<ProxyObject>());
         if (bufobj->is<ProxyObject>()) {
             /*
              * Normally, NonGenericMethodGuard handles the case of transparent
@@ -791,44 +782,48 @@ class TypedArrayObjectTemplate : public TypedArrayObject
                 JS_ReportErrorASCII(cx, "Permission denied to access object");
                 return nullptr;
             }
-            if (IsArrayBuffer(wrapped) || IsSharedArrayBuffer(wrapped)) {
-                /*
-                 * And for even more fun, the new view's prototype should be
-                 * set to the origin compartment's prototype object, not the
-                 * target's (specifically, the actual view in the target
-                 * compartment will use as its prototype a wrapper around the
-                 * origin compartment's view.prototype object).
-                 *
-                 * Rather than hack some crazy solution together, implement
-                 * this all using a private helper function, created when
-                 * ArrayBufferObject was initialized and cached in the global.
-                 * This reuses all the existing cross-compartment crazy so we
-                 * don't have to do anything *uniquely* crazy here.
-                 */
 
-                RootedObject protoRoot(cx, proto);
-                if (!protoRoot) {
-                    if (!GetBuiltinPrototype(cx, JSCLASS_CACHED_PROTO_KEY(instanceClass()), &protoRoot))
-                        return nullptr;
-                }
-
-                FixedInvokeArgs<3> args(cx);
-
-                args[0].setNumber(byteOffset);
-                args[1].setInt32(lengthInt);
-                args[2].setObject(*protoRoot);
-
-                RootedValue fval(cx);
-                if (!getOrCreateCreateArrayFromBufferFunction(cx, &fval))
-                    return nullptr;
-
-                RootedValue thisv(cx, ObjectValue(*bufobj));
-                RootedValue rval(cx);
-                if (!js::Call(cx, fval, thisv, args, &rval))
-                    return nullptr;
-
-                return &rval.toObject();
+            if (!IsArrayBuffer(wrapped) && !IsSharedArrayBuffer(wrapped)) {
+                JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_TYPED_ARRAY_BAD_ARGS);
+                return nullptr; // must be arrayBuffer
             }
+
+            /*
+             * And for even more fun, the new view's prototype should be
+             * set to the origin compartment's prototype object, not the
+             * target's (specifically, the actual view in the target
+             * compartment will use as its prototype a wrapper around the
+             * origin compartment's view.prototype object).
+             *
+             * Rather than hack some crazy solution together, implement
+             * this all using a private helper function, created when
+             * ArrayBufferObject was initialized and cached in the global.
+             * This reuses all the existing cross-compartment crazy so we
+             * don't have to do anything *uniquely* crazy here.
+             */
+
+            RootedObject protoRoot(cx, proto);
+            if (!protoRoot) {
+                if (!GetBuiltinPrototype(cx, JSCLASS_CACHED_PROTO_KEY(instanceClass()), &protoRoot))
+                    return nullptr;
+            }
+
+            FixedInvokeArgs<3> args(cx);
+
+            args[0].setNumber(byteOffset);
+            args[1].setInt32(lengthInt);
+            args[2].setObject(*protoRoot);
+
+            RootedValue fval(cx);
+            if (!getOrCreateCreateArrayFromBufferFunction(cx, &fval))
+                return nullptr;
+
+            RootedValue thisv(cx, ObjectValue(*bufobj));
+            RootedValue rval(cx);
+            if (!js::Call(cx, fval, thisv, args, &rval))
+                return nullptr;
+
+            return &rval.toObject();
         }
 
         if (!IsArrayBuffer(bufobj) && !IsSharedArrayBuffer(bufobj)) {

js/xpconnect/tests/chrome/test_xrayToJS.xul

@@ -753,6 +753,10 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=933681
       is(t.length, 10, "Length accessor works over Xrays")
       is(t.byteLength, t.length * window[c].prototype.BYTES_PER_ELEMENT, "byteLength accessor works over Xrays")
 
+      // Can create TypedArray from content ArrayBuffer
+      var buffer = new iwin.ArrayBuffer(8);
+      eval(`new ${c}(buffer);`);
+
       var xray = new iwin[c](0);
       var xrayTypedArrayProto = Object.getPrototypeOf(Object.getPrototypeOf(xray));
       testProtoCallables(inheritedCallables, new iwin[c](0), xrayTypedArrayProto, typedArrayProto);