[tor-bugs] #32053 [Applications/Tor Browser]: Tor Browser bundles based on Firefox 68 ESR are not reproducible (LLVM optimization issue)

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#32053: Tor Browser bundles based on Firefox 68 ESR are not reproducible (LLVM
optimization issue)
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 Reporter:  gk                                   |          Owner:  gk
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  Immediate                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Critical                             |     Resolution:
 Keywords:  TorBrowserTeam201911, tbb-9.0-must,  |  Actual Points:
  tbb-9.0-issues, tbb-regression, tbb-9.0.1-can  |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Okay, some good news. Testing with clang 9 + the patch for
 https://reviews.llvm.org/D70376 gives me reproducible output while without
 it it does not. Thus, the bug we are chasing seems to got fixed somewhere
 between 8.0.0 and 9.0.0 (assuming that the https://reviews.llvm.org/D70376
 fix is equivalent to Eli's [https://bugs.llvm.org/attachment.cgi?id=22803
 backported patch for 8.0.0] which I'll check soon). I'll do another
 bisecting figuring out which commit actually fixed the issue we hit while
 still trying pin the exact optimization down that is troubling us.

 Another good news is that Mozilla seems to be
 [https://bugs.llvm.org/show_bug.cgi?id=44147 ready to find this kind of
 bugs, too], and potentially earlier than we from now on so that we
 hopefully have been dealing with this kind of stuff for the last time. I
 guess that got solved on Mozilla's side by
 https://bugzilla.mozilla.org/show_bug.cgi?id=1577212.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32053#comment:50>
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