[Webkit-unassigned] [Bug 201366] New: Tail Deleted Frames shown in Web Inspector are sometimes incorrect (Shadow Chicken)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=201366

            Bug ID: 201366
           Summary: Tail Deleted Frames shown in Web Inspector are
                    sometimes incorrect (Shadow Chicken)
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: joepeck at webkit.org
                CC: drousso at apple.com, fpizlo at apple.com,
                    keith_miller at apple.com, mark.lam at apple.com,
                    sbarati at apple.com

Created attachment 377763

  --> https://bugs.webkit.org/attachment.cgi?id=377763&action=review

[TEST PAGE] test.html

Tail Deleted Frames shown in Web Inspector are sometimes incorrect (Shadow Chicken)

Steps to reproduce:
1. Inspect test page
  => Show Call Stack in Web Inspector debugger sidebar

Expected:

  Call Stack:
  [green f] a
  [gray  f] b
  [gray  f] c
  [green f] startABC

Actual:

  Call Stack:
  [green f] a
  [gray  f] b
  [gray  f] c
  [gray  f] THIS_DOES_NOT_CALL_c
  [gray  f] THIS_DOES_NOT_CALL_c
  ...
  [gray  f] THIS_DOES_NOT_CALL_c
  [green f] startABC


Test page:

<script>
"use strict";
function a() {
    let x = 20;
    debugger;
    x;
    return x;
}
function b() {
    let y = 40;
    return a.call({aThis: 2});
}
function c() {
    let z = 60;
    return b.call({bThis: 1}); 
}
function startABC() {
    for (let i = 0; i < 500; ++i)
        THIS_DOES_NOT_CALL_c();
    c.call({cThis: 0});
}
function THIS_DOES_NOT_CALL_c() {
    return Math.random();
}
setInterval(startABC);
</script>

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