[tor-bugs] #22832 [Applications/Tor Browser]: libwebrtc and snowflake are not being built reproducibly (unless you build in the same month)

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#22832: libwebrtc and snowflake are not being built reproducibly (unless you build
in the same month)
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     Reporter:  gk                        |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Very High                 |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Major                     |   Keywords:  tbb-gitian
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 I already ran into this problem when building 7.0a4 but did not have time
 to investigate it back then: I did only a partial rebuild (not touching
 snowflake as this was not necessary) but boklm did a full build. The
 result was a different `snowflake-client`.

 Now this happened with the build for 7.5a2 again. The diff is:
 {{{
 --- /dev/fd/63  2017-07-06 09:57:34.341983842 +0200
 +++ /dev/fd/62  2017-07-06 09:57:34.341983842 +0200
 @@ -750821,7 +750821,7 @@
  00b74e40: 6e6e 656c 3d25 642c 2025 6c75 2900 7468  nnel=%d, %lu).th
  00b74e50: 6973 203d 3d20 675f 746f 705f 6d61 6e61  is == g_top_mana
  00b74e60: 6765 7200 4368 6563 6b20 6661 696c 6564  ger.Check failed
 -00b74e70: 3a20 6675 6e63 2e20 004a 756e 2030 3420  : func. .Jun 04
 +00b74e70: 3a20 6675 6e63 2e20 004a 756c 2030 3220  : func. .Jul 02
  00b74e80: 3230 3137 2030 353a 3030 3a30 3000 4368  2017 05:00:00.Ch
  00b74e90: 6563 6b20 6661 696c 6564 3a20 6269 6e64  eck failed: bind
  00b74ea0: 5f73 7461 7465 5f2e 2000 2c3c 2a00 4368  _state_. .,<*.Ch
 }}}
 That seems to be a bit weird given the actual build date but boklm had the
 idea it could be the first Sunday of the month/week getting embedded.

 And, indeed, as boklm pointed out `/build/write_build_date_header.py`
 seems to do such a thing.

 I can trace the problem back to `build_time.o` in the libwebrtc .a file.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22832>
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