138859 2014-11-18 19:10:45 -0800 global function declaration should be throwing a TypeError if trying to override a readonly property 2025-12-02 23:33:44 -0800 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) Mac (Intel) OS X 10.9 NEW EasyFix, GoodFirstBug, InRadar P2 Normal --- 1 daejunpark webkit-unassigned ggaren kling msaboff oliver vasan.s webkit-bug-importer oldest_to_newest 1049698 0 daejunpark 2014-11-18 19:10:45 -0800 According to ES5, Section 10.5 Declaration Binding Instantiation, Step 5.e.iv, http://es5.github.io/#x10.5 a duplicate global function declaration throws a TypeError exception, when the existing property is not configurable and: - an accessor descriptor, - or, not writable, - or, not enumerable. For example, the following code is supposed to throw a TypeError exception for each duplicate function declaration, "f0", "f1", "f2", and "f3": Object.defineProperty(this, "f0", { "get" : undefined, "set" : undefined, "enumerable" : false, "configurable" : false }); eval(" function f0() { return 0; } "); // TypeError Object.defineProperty(this, "f1", { "value" : 0, "writable" : false, "enumerable" : false, "configurable" : false }); eval(" function f1() { return 0; } "); // TypeError Object.defineProperty(this, "f2", { "value" : 0, "writable" : true, "enumerable" : false, "configurable" : false }); eval(" function f2() { return 0; } "); // TypeError Object.defineProperty(this, "f3", { "value" : 0, "writable" : false, "enumerable" : true, "configurable" : false }); eval(" function f3() { return 0; } "); // TypeError However, Safari does not report any exception, while Chrome and Firefox correctly throw the TypeError exceptions. I've tested this using the Web Inspector console of Safari 7.0.4. Thanks, Daejun 1049786 1 oliver 2014-11-19 08:51:54 -0800 Retitling to reflect actual bug - it's not due to a duplicate function. We're short circuiting creation of a new global property when we decide to shadow and that means we skip the readonly check on the existing property. Whoops. 1049846 2 webkit-bug-importer 2014-11-19 11:17:52 -0800 <rdar://problem/19032865> 2162843 3 vasan.s 2025-12-02 23:33:44 -0800 I think this is already fixed in 355e9d25900a300375b1b68576f926278d8b5903. JavaScriptCore from Safari Version 26.1 (21622.2.11.11.9) does throw TypeError for all four cases.