511998 - Arguments object properties no longer alias arguments after the function returns

Status: RESOLVED DUPLICATE of bug 478174

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

var get, put;
function f(a) {
    var args = arguments;
    get = function () { return a;};
    put = function (x) { args[0] = x; };
}
f('old');
put('new');
assertEq(get(), 'new');

When f returns, we call js_PutCallObject and js_PutArgsObject, and separate copies of the locals are stored in the two objects. put() only affects arguments, not the Call object.

I think ES3 requires `arguments[0]` and `a` to keep aliasing forever.

Comment 1

[Brendan Eich [:brendan]]

Yes, ES3 does specify that.

Richard Cornford pointed this out here:

https://mail.mozilla.org/pipermail/es-discuss/2008-July/006618.html

I forgot to file a bug. Kind of on purpose :-P.

/be

Comment 2

[Jason Orendorff [:jorendorff]]

478174 has a nicer test case.