197134 2019-04-19 21:01:09 -0700 Can't create a const attribute via the JSC C API 2019-04-22 15:39:13 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED WORKSFORME P2 Normal --- 197133 1 simon.fraser webkit-unassigned ggaren keith_miller saam sam simon.fraser ysuzuki oldest_to_newest 1529030 0 simon.fraser 2019-04-19 21:01:09 -0700 There's no way that I could find to create a readonly, const attribute on a class via the JSC C API. I need a I need the C equivalent of making an attribute with { JSC::PropertyAttribute::DontDelete | JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::ConstantInteger, NoIntrinsic } This is for DumpRenderTree/WebKitTestRunner. 1529122 1 sam 2019-04-20 19:39:52 -0700 I think you can do this with using the staticValues array for a class definition: static JSValueRef GetConstantValue(JSContextRef ctx, JSObjectRef, JSStringRef, JSValueRef*) { return JSValueMakeNumber(ctx, 7); } JSStaticValue StaticValueArray[] = { { "constantValue", GetConstantValue, 0, kJSPropertyAttributeReadOnly | kJSPropertyAttributeDontDelete }, { 0, 0, 0, 0 } }; If memory serves me, JSC::PropertyAttribute::ConstantInteger is an optimization, and doesn't change behavior. 1529123 2 sam 2019-04-20 19:44:37 -0700 Or, if you don't want to go the callback route, you can create the properties after the object has been created. JSObjectSetProperty(ctx, objectToAddPropertyTo, JSStringCreateWithUTF8CString("constantValue), JSValueMakeNumber(ctx, 7), kJSPropertyAttributeReadOnly | kJSPropertyAttributeDontDelete, &exceptionPtr); 1529299 3 saam 2019-04-22 10:49:35 -0700 (In reply to Sam Weinig from comment #2) > Or, if you don't want to go the callback route, you can create the > properties after the object has been created. > > JSObjectSetProperty(ctx, objectToAddPropertyTo, > JSStringCreateWithUTF8CString("constantValue), JSValueMakeNumber(ctx, 7), > kJSPropertyAttributeReadOnly | kJSPropertyAttributeDontDelete, > &exceptionPtr); I think this is what you want. From the JS spec, these things mean: - kJSPropertyAttributeReadOnly means you can't Put to the property. E.g, if you have kJSPropertyAttributeReadOnly property "foo", "x.foo = 42" won't succeed. This makes it a "writable: false" property. - kJSPropertyAttributeDontDelete means the property descriptor is non-configurable. E.g, "delete x.foo" will fail. So will "Object.defineProperty(x, "foo", { ... })" 1529438 4 simon.fraser 2019-04-22 15:39:13 -0700 OK, that seems to work.