[tbb-bugs] #21328 [Applications/Tor Browser]: Move to clang 3.8.0 for Tor Browser's clang-based macOS toolchain

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#21328: Move to clang 3.8.0 for Tor Browser's clang-based macOS toolchain
-------------------------------------------------+-------------------------
 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  task                                 |         Status:  new
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-gitian, ff52-esr, tbb-7.0-must,  |  Actual Points:
  TorBrowserTeam201703, GeorgKoppen201703        |
Parent ID:  #21147                               |         Points:
 Reviewer:                                       |        Sponsor:
                                                 |  Sponsor4
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Changes (by gk):

 * cc: boklm (added)


Comment:

 Replying to [comment:10 gk]:
 > It seems moving to the new toolchain has reproducibility problems as a
 result. :( I just bumped the Debian distro to Jessie and put clang
 together according to https://bugzilla.mozilla.org/show_bug.cgi?id=1273981
 and the resulting dmgs don't match anymore. Using the old clang compiler
 does not have the same problems.

 Okay, attached is the diff. I used https://gitweb.torproject.org/user/gk
 /tor-browser-bundle.git/log/?h=bug_21328_v3. The problematic commit is:
 https://gitweb.torproject.org/user/gk/tor-browser-
 bundle.git/commit/?h=bug_21328_v3&id=868433db05b3dc57926e32b79213383483f15f59.
 Testing with the ones before that one gives me matching builds on the same
 build machine. Some things we could do to find the problem:

 1) We could try to pinpoint where exactly the issue is. Is it in tor code
 or in openssl code, or...?
 2) We could test whether the update to Jessie is causing this (by taking
 https://gitweb.torproject.org/user/gk/tor-browser-
 bundle.git/commit/?h=bug_21328_v3&id=6ff54b812b08f3b64fb277f0541dfd9562bf3d6e
 and just bump everything to Jessie)
 3) We could just use the clang part for compiling the remaining utils and
 tor (and not include `libcxx` nor `libcxxabi` which should not be needed
 anyway) to make sure the issue is inside `clang`.
 4) Assuming this is indeed in `clang`, because the investigation done in
 1) - 3) shows that, we could do some bisecting finding the problematic
 commit.

 boklm: Can you take that one from here?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21328#comment:12>
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