[tbb-bugs] #26475 [Applications/Tor Browser]: ESR60-based .dmg images are not built reproducibly with Stylo enabled using rustc > 1.25.0

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#26475: ESR60-based .dmg images are not built reproducibly with Stylo enabled using
rustc > 1.25.0
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_information
 Priority:  Very High                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-rbm, TorBrowserTeam201807,       |  Actual Points:
  GeorgKoppen201807                              |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Replying to [comment:23 gk]:
 > Replying to [comment:22 alexcrichton]:
 > > Hm interesting! I wonder if this is perhaps related to
 https://github.com/rust-lang/rust/issues/52044? That claims it was fixed
 with the most recent LLVM upgrade. Are you able to reproduce the non-
 determinism on the most recent nightly?
 >
 > Aha! That sounds promising and I certainly feel glandium's "This is
 driving me crazy", so this should be the issue then, right? ;)
 >
 > That said, I compiled the nightly from 2018-07-13 which should contain
 the LLVM upgrade and I can't reproduce the problem anymore. However, I
 can't either when compiling the one from from 2018-07-11 which should
 *not* contain the LLVM upgrade (it's based on commit
 e5f6498d3d5c9dac841009d7b49738923826af75). So, it seem the LLVM uprade
 (alone) is not enough to explain this bug, or am I missing something?

 On the other hand testing your script from https://github.com/rust-
 lang/rust/issues/52044#issuecomment-402349038 shows easily that the one
 from 2018-07-13 is good while the one from 2018-07-11 is not. I guess I
 tried the Firefox build just not often enough with 2018-07-11...

 So, what's the suggested way to fix that? What until a new stable compiler
 with a fix for it is out (I guess that's 1.28.0) and use that one?

 Althought, tbh, it's scary to hope this is finally fixed without exactly
 knowing what the issue was. I might try to look closer at it.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26475#comment:25>
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