[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)
-------------------------------------------------+-------------------------
 Reporter:  gk                                   |          Owner:  gk
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Immediate                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Critical                             |     Resolution:
 Keywords:  tbb-9.0-must, tbb-9.0-issues, tbb-   |  Actual Points:  11.5
  regression, tbb-9.0.1-can,                     |
  TorBrowserTeam201912R, GeorgKoppen201912       |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------
Changes (by gk):

 * keywords:
     tbb-9.0-must, tbb-9.0-issues, tbb-regression, tbb-9.0.1-can,
     TorBrowserTeam201912
     =>
     tbb-9.0-must, tbb-9.0-issues, tbb-regression, tbb-9.0.1-can,
     TorBrowserTeam201912R, GeorgKoppen201912
 * status:  assigned => needs_review
 * actualpoints:   => 11.5


Comment:

 `bug_32053_v5` (https://gitweb.torproject.org/user/gk/tor-browser-
 build.git/commit/?h=bug_32053_v5&id=b3863530eb585d849a1de0e4eba6690e589954e6)
 is up for review.

 I've been running into two reproducibility issues while debugging. The one
 Alex reported (bug 43909) we need to fix, I am not sure about the other
 one, bug 42574. The later got fixed in clang 9 and I only encountered it
 while testing an LLVM 8 `opt` on a non-optimized style bitcode file built
 with Rust 1.32.0. When built with 1.34.2 which we actually uses I don't
 hit the bug.

 However, it's not clear whether any of the issues (or mabye even unknown
 ones) we hit on other platforms than macOS and 32bit Linux is caused by
 bug 42575, thus I think it's safer to backport that fix as well.

 Alex: a big thank you to you for your invaluable help. Without it hunting
 down and fixing the bug(s) would have taken much longer.

 boklm: please add your points for #32052 to this ticket, too.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32053#comment:53>
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