[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:  dcf
     Type:  defect                    |         Status:  assigned
 Priority:  Very High                 |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Major                     |     Resolution:
 Keywords:  tbb-gitian                |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by dcf):

 I searched for the date strings in a build I had lying around from
 #19001/#22831 (Snowflake for mac), and they weren't there. I think the
 difference is [https://gitweb.torproject.org/user/dcf/tor-browser-
 bundle.git/commit/?h=snowflake-
 mac-4&id=80b8e83b0d6ae349df4bcaeba34d6002e1bc7ea3 this commit] which
 reduces the scope of .o files that get included into libwebrtc-magic.a. I
 discovered, while working on the mac descriptor, that we could reduce the
 number of .o files (because some of them are unit tests or build helpers).
 I did it for size reasons, but as a side effect it seems that it also
 excludes build_time.o. The commit I linked was just to make the linux
 descriptor uniform with the new mac descriptor.

 Let me know if that commit works for you (feel free to edit as necessary).
 If we want to set `override_build_date` as well (even though it seems
 unnecessary it might be a good idea for future insurance), this seems to
 be the expected format (taken from build/write_build_date_header.py). I
 haven't tested it, but I'm starting a build to do so now.
 {{{
 GN_ARGS+=" override_build_date=\"$(date --utc --date="$REFERENCE_DATETIME"
 +"%b %d %Y %H:%M:%S")\""
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22832#comment:3>
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