Bug 244190 – JSC DFG Number.prototype.toString should throw an exception when the parameter is undefined, null or true

• Status: NEW
• Component: JavaScriptCore

[EntryHi]

function foo(a) {
  try {
    print(Number.prototype.toString.call(a))
  } catch (e) {
    print("error")
  }
}
noInline(foo);
for (var i = 0; i < 200; i++) {
  foo(10); 
  foo(true); //throw an exception
  //foo(null); // throw an exception
  //foo(undefined); // throw an exception
}



With the above script as input to JSC, run JSC with the following parameters:
./jsc test.js --useConcurrentJIT=0 --jitPolicyScale=1

In interpreter, Number.prototype.toString throw an exception. However, in JIT, Number.prototype.toString does not throw an exception.

DFG JIT uses DoubleRep node to ensure that the parameter of Number.prototype.toString is a number, if not, OSRExit should occur.
However, undefined, null and true can pass the check of the DoubleRep node, no OSRExit occurs. These parameters are passed to toString, no exception is thrown.

[Radar WebKit Bug Importer]

<rdar://problem/99268958>

[EntryHi]

Hello, I am a PhD student majoring in computer security. Currently engaged in research related to JavaScript engine. I submitted 6 bugs to WebKit Bugmozilla three weeks ago. Currently only one has been confirmed to reply and commit. These bugs are very important to the results of my dissertation and whether I can graduate on time. Can I sincerely ask you to take time out of your busy schedule to confirm or reply. Thank you very much.

[Sosuke Suzuki]

Pull request: https://github.com/WebKit/WebKit/pull/25090