[tbb-bugs] #25087 [Obfuscation/Snowflake]: Snowflake broken if no libatomic on host (e.g. Lubuntu 17 64 bits)

Tor Bug Tracker & Wiki blackhole at torproject.org
Fri Feb 2 07:25:01 UTC 2018

#25087: Snowflake broken if no libatomic on host (e.g. Lubuntu 17 64 bits)
 Reporter:  cypherpunks            |          Owner:  tbb-team
     Type:  defect                 |         Status:  needs_information
 Priority:  Medium                 |      Milestone:
Component:  Obfuscation/Snowflake  |        Version:
 Severity:  Normal                 |     Resolution:
 Keywords:                         |  Actual Points:
Parent ID:                         |         Points:
 Reviewer:                         |        Sponsor:

Comment (by yawning):

 Replying to [comment:11 arma]:
 > Speaking of atomic, there's an intriguingly related ChangeLog entry to
 Tor itself in
 > {{{
 >     - Use stdatomic.h where available, rather than mutexes, to implement
 >       atomic_counter_t. Closes ticket 23953.
 > }}}
 > But on first glance it looks like that's headers, not the library. But,
 does that mean that if Tor Browser builds Tor on a system with libatomic
 headers, then Tor Browser's Tor will expect a libatomic it can use?

 "Depends".  libatomic is what GCC will fall back to if does not have
 native code generation capability for an atomic operation on a given
 target.  If Tor Browser is targeting something where GCC ends up doing
 that, then yes, Tor Browser's Tor will also expect a working libatomic.

 > as we wait maybe everybody will get libatomic.

 In an ideal world, GCC will support the relevant code generation for all
 the targets that the bundle is shipped for, and no one will need

 After thinking about this for a bit, I'm of the opinion that as long as
 the GCC used to build Tor Browser generates code that links to it, Tor
 Browser should bundle it, much like how libstdc++ is bundled.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25087#comment:12>
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