[MacPorts] #46775: tmux hangs on Yosemite

[MacPorts]

#46775: tmux hangs on Yosemite
-----------------------------+------------------------
  Reporter:  arne.schmitz@…  |      Owner:  tessarek@…
      Type:  defect          |     Status:  new
  Priority:  Normal          |  Milestone:
 Component:  ports           |    Version:  2.3.3
Resolution:                  |   Keywords:
      Port:  tmux            |
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Comment (by chris_johnsen@…):

 I can confirm that using `__DARWIN_VERS_1050` does offer a ''partial''
 workaround for older OS X releases. The problem is that where that
 workaround simply stopped working on older releases, it causes significant
 problems on Yosemite. The scenario in question is this:

 1. In a GUI session (e.g. a ''Terminal'' or ''iTerm'' window), start a
 fresh ''tmux'' server.
 1. Observe that some special commands still work normally from inside the
 ''tmux'' session (i.e. the same as in a plain ''Terminal'' window):
     * `pbpaste` and `pbcopy` both work to access the pasteboard
     * `open` can open files, folders, URLs in the normal GUI-based
 applications
     * various other things: https://github.com/ChrisJohnsen/tmux-MacOSX-
 pasteboard/blob/master/Usage.md#beyond-pasteboard-access
 1. Logout of the GUI session (while leaving the ''tmux'' server running).
 1. Start a new GUI session, attach to the previously started ''tmux''
 session.
 1. Create a new ''tmux'' window.

 On previous OS X releases this would work OK, but new and existing
 ''tmux'' children would have lost the ability to use those “special
 commands” above (i.e. the `__DARWIN_VERS_1050` workaround is no longer
 effective at this point). On Yosemite, creating the new window in the last
 step hangs. The hang actually happens inside some internal GCD/XPC/Mach
 invocations that happen to be built into several basic library calls (e.g.
 getpwuid and localtime). The following backtrace was captured from running
 `date` in the above-described context:

 {{{
 (lldb) pr at -p 36663
 Process 36663 stopped
 warning: Executable module changed from "/bin/ls" to "/bin/date".
 (lldb) bt
 * thread #1: tid = 0x17a432, 0x00007fff8d2c74de
 libsystem_kernel.dylib`mach_msg_trap + 10, queue = 'com.apple.main-
 thread', stop reason = signal SIGSTOP
   * frame #0: 0x00007fff8d2c74de libsystem_kernel.dylib`mach_msg_trap + 10
     frame #1: 0x00007fff8d2c664f libsystem_kernel.dylib`mach_msg + 55
     frame #2: 0x00007fff8646627e libxpc.dylib`xpc_pipe_routine + 252
     frame #3: 0x00007fff8646ee02 libxpc.dylib`_xpc_interface_routine + 163
     frame #4: 0x00007fff86473c45 libxpc.dylib`bootstrap_look_up3 + 248
     frame #5: 0x00007fff86473b36 libxpc.dylib`bootstrap_look_up2 + 47
     frame #6: 0x00007fff8955dd2e
 libsystem_notify.dylib`___notify_lib_init_block_invoke + 58
     frame #7: 0x00007fff8e389c13
 libdispatch.dylib`_dispatch_client_callout + 8
     frame #8: 0x00007fff8e389b26 libdispatch.dylib`dispatch_once_f + 117
     frame #9: 0x00007fff8955a3fc libsystem_notify.dylib`_notify_lib_init +
 944
     frame #10: 0x00007fff8955b24c
 libsystem_notify.dylib`notify_register_check + 159
     frame #11: 0x00007fff81d1cb9c libsystem_c.dylib`notify_register_tz +
 204
     frame #12: 0x00007fff81d1c6c4 libsystem_c.dylib`tzsetwall_basic + 213
     frame #13: 0x00007fff81d1c880 libsystem_c.dylib`_st_tzset_basic + 363
     frame #14: 0x00007fff81d1dfb0 libsystem_c.dylib`localtime + 206
     frame #15: 0x000000010c5ac4b3 date`___lldb_unnamed_function13$$date +
 1827
     frame #16: 0x00007fff8d5625c9 libdyld.dylib`start + 1
 }}}


 So, `__DARWIN_VERS_1050` is somewhat helpful on older releases (I just re-
 tested this on 10.9, but I can not currently go back any further; though I
 remember testing on 10.6 when I first wrote ''reattach-to-user-namespace''
 almost four years ago).

 But `__DARWIN_VERS_1050` is harmful on Yosemite in a context that could be
 a quite common for ''tmux'' users (i.e. leaving a ''tmux''-based terminal
 session running while logging out the main GUI session).

 I would suggest only using `__DARWIN_VERS_1050` on pre-Yosemite releases.
 Yosemite seems to have its own fix for accessing the pasteboard in the
 above-described context, so that at least mitigates some of the problems
 that `__DARWIN_VERS_1050` would normally help with (pre-logout; other
 commands like `open` will fail post-logout, but this is arguably better
 than causing every child of ''tmux'' to eventually hang).

-- 
Ticket URL: <https://trac.macports.org/ticket/46775#comment:2>
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