[tor-bugs] #17858 [Applications/Tor Browser]: Creating incremental MAR files for the hardened builds is broken

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#17858: Creating incremental MAR files for the hardened builds is broken
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 Reporter:  gk                                   |          Owner:  mcs
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-gitian, tbb-hardened,            |  Actual Points:
  GeorgKoppen201512, TorBrowserTeam201608R       |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------
Changes (by mcs):

 * status:  assigned => needs_review
 * keywords:  tbb-gitian, tbb-hardened, GeorgKoppen201512,
     TorBrowserTeam201608 => tbb-gitian, tbb-hardened, GeorgKoppen201512,
     TorBrowserTeam201608R


Comment:

 My ASan-enabled mbsdiff ran for hours without completing while trying to
 generate diffs for libXUL (eventually I gave up and killed it). The
 problem appeared to be CPU usage, not VM exhaustion.

 I think the simplest solution is to avoid using ASan when generating the
 MAR files. Here is a patch:
 https://gitweb.torproject.org/user/brade/tor-
 browser.git/commit/?h=bug17858-01&id=2126d94c8191880bdb20370566c5acc13b817ff3

 When I tested this, my system took 187 seconds to finish a 'make
 incrementals-alpha' command and produced a tor-browser-
 linux64-6.5a1-hardened-6.5a2-hardened_ALL.incremental.mar file of size
 23MB (the full MAR file is 110MB).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17858#comment:17>
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