The following test asserts on mozilla-central revision 17af008937e3 (options -m -a -n): a = 'a'; b = [,]; exhaustiveSliceTest("exhaustive slice test 1", a); exhaustiveSliceTest("exhaustive slice test 2", b); function exhaustiveSliceTest(testname, a){ x = 0 var y = 0; countHeap(); for (y=a.length; y + a.length; y--) var b = a.slice(x,y); } This one involves the shell-only function "countHeap", but I don't know if this is a shell-only bug or just revealing a real bug. Maybe related to bug 746150? S-s until triaged.
taking a guess that countHeap() shouldn't affect inference correctness and assigning sg:critical
autoBisect shows this is probably related to the following changeset: The first bad revision is: changeset: 86695:fbef6a165cf8 user: Bill McCloskey date: Fri Feb 10 18:32:08 2012 -0800 summary: Bug 723313 - Stop using conservative stack scanner for VM stack marking (r=luke,bhackett)
Marking flags based on regression window in comment 2.
Created attachment 619797 [details] [diff] [review] patch Here's the scenario: 1. Code sets y to 0. 2. GC happens. y is dead, so we overwrite it with undefined. 3. Code sets y to 1. As an optimization, it doesn't update the type tag. It incorrectly assumes it hasn't changed since step 1. The easiest thing to do is to leave the type tag alone in step 2 while fixing up any pointers. The only tags we actually need to worry about are object and string. And we can come up with a dummy string and a dummy object as replacements. The only concern is that this code shouldn't cause the dummy object to be leaked. For objects, I used the global as the dummy. Luke says that the stack frame shouldn't outlive its global, so this seems safe.
*** Bug 746150 has been marked as a duplicate of this bug. ***
https://hg.mozilla.org/integration/mozilla-inbound/rev/c296a4cfe0d6
https://hg.mozilla.org/mozilla-central/rev/c296a4cfe0d6
JSBugMon: This bug has been automatically verified fixed.
Comment on attachment 619797 [details] [diff] [review] patch [Approval Request Comment] Regression caused by (bug #): bug 723313 User impact if declined: This may cause crashes or be exploitable. Testing completed (on m-c, etc.): On m-c. Risk to taking this patch (and alternatives if risky): Low. We used to overwrite a stack slot with a dummy value, now we overwrite it with a slightly different dummy value. String changes made by this patch: None
https://hg.mozilla.org/releases/mozilla-aurora/rev/6114cf84a407 https://hg.mozilla.org/releases/mozilla-beta/rev/7dfc84b36390
*** Bug 747334 has been marked as a duplicate of this bug. ***
*** Bug 748547 has been marked as a duplicate of this bug. ***
A testcase for this bug was automatically identified at js/src/jit-test/tests/basic/bug747926.js.
or
