[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, GeorgKoppen201808,          |  Actual Points:
  TorBrowserTeam201808                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Alright, so, the problematic commit is
 6b7b6b63a928479a29d9fc1282e553e409c66934. I tried to bisect LLVM to find
 out the bad revision. I compiled just LLVM separately and used `--llvm-
 root` to point to it during the rust build. It turns out that doing that,
 even with just the llvm code copied out of rust/src/llvm being on commit
 6b7b6b63a928479a29d9fc1282e553e409c66934 is fine. However, double-
 checking, building LLVM during the usual rust build (i.e. without `--llvm-
 root`) still reproduces the bug.

 Thus, I can only think of two reasons causing the reprouducibility issue:

 1) The LLVM part is compiled differently within rust than I did. The
 compiler used is the same, though, not sure what other flags could cause
 this. I am doing
 {{{
 cmake .. -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$distdir
 -DCMAKE_BUILD_TYPE:STRING=Release -DLLVM_INSTALL_UTILS=on $LLVM_HOME
 }}}
 in the `--llvm-root` build which seems to be not overly fancy.

 2) There are additional pieces getting compiled in/used during the LLVM
 compilation done during the rust build that are causing the problem.

 I need to think more about how to proceed but, Alex, if you have any ideas
 that would be appreciated. :)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26475#comment:33>
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