Bug 40355 – Exception loading Google Wave in Safari 5

• Component: WebCore JavaScript
• Status: RESOLVED DUPLICATE

[noel gordon]

Load Google Wave in Safari 5 (win32, and/or mac/osx 10.5), the
javascript console reports:

   RangeError: Maximum call stack size exceeded.

and Google Wave stops working. Test results/reduction attached

  OSX Firefox 3.6    OK  
  OSX Safari 4.0.4   OK
  OSX Chrome 5.0.375 OK
  OSX Safari 5.0     FAIL

[noel gordon]

Created attachment 58221 [details]
Test Case

[Gavin Barraclough]

<rdar://problem/8076614>

[Steve Dunham]

This issue seems to only occur when Safari 5 is run in 32-bit mode.

[Steve Dunham]

If you replace:

    tmp = (tmp >> 1);

with

   var tmp2 = (tmp >> 1);
   tmp = tmp2;

the testcase passes.

If you instrument the original testcase with print statements, tmp.toString() is "3" before the shift operation and "3.0000000000000004" afterwards.

[Joel Webber]

The following is a related, but slightly narrower form of the bug:

function merge(d,e,f) {
  var h,i,j,k;
  h = e - d;
  if (h < 3) {
    return
  }
  j = d + f;
  i = e + f;
  k = j + (i - j >> 1);
  merge(j,k,-f);
  merge(k,i,-f);
}
merge(0, 5, 0);

From the console, when you set a breakpoint in merge(2, 5, 0):
> i
   5
> j
   2
> (i - j)
   3
> ((i - j) >> 1)
   1
> j + ((i - j) >> 1)
   5 <= WTF?!

[Steve Dunham]

Further reduced test case:

function test() {
    var off = -0;
    var tmp = 5 + off;
    var tmp2 = (tmp >> 1);
    tmp = tmp >> 1;
    if (tmp != tmp2)
        document.getElementById("result").innerHTML = "fail "+tmp+" != "+tmp2;
    else
        document.getElementById("result").innerHTML = "pass";
}

Gives:
  fail 5.000000000000002 != 2

It looks like adding "-0" to an integer results in a value that will right shift correctly in some contexts but not in others.  (Note that tmp2 holds the correct value, but tmp does not.)

[Oliver Hunt]

*** This bug has been marked as a duplicate of bug 40367 ***