[Bug 40285] Re: libgcc_s.so.1 must be installed for pthread_cancel to work

[Juergen Perlinger]

I was probably wrong -- it seems this is not related to running as
restricted user per se.

Using ldd shows no reference to libgcc_s in the binary, even if I build
from source and explicitly add '-lgcc_s' to the linker command line.
strace shows no signs of using libgcc_s unless put into the preload
environment. And ntpd always comes to a grinding halt when not run as
root unless the preload environment is used. Running as root does not
crash just by lucky chance, I think.

I get the same results  with gcc-4.7 and gcc-4.8 on a freshly installed
x64/amd64 Saucy.

As a workaround, I put libgcc_s.so.1 into /etc/ld.so.preload, since this
should help most applications that run into this problem. Though this
only cures the symptom: It's still not clear WHY there is no reference
to the SO in the binary... Could there be some toolchain trouble?

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https://bugs.launchpad.net/bugs/40285

Title:
  libgcc_s.so.1 must be installed for pthread_cancel to work

Status in “gcc-3.3” package in Ubuntu:
  Fix Released
Status in “gcc-4.4” package in Ubuntu:
  Confirmed
Status in “gcc-4.6” package in Ubuntu:
  Confirmed
Status in “pound” package in Ubuntu:
  Invalid

Bug description:
  the error:

   libgcc_s.so.1 must be installed for pthread_cancel to work

  is printed by applications using pthreads and calling:

  set the thread to check or cancel:
  thread_setcancelstate (PTHREAD_CANCEL_ENABLE, NULL);
          pthread_setcanceltype (PTHREAD_CANCEL_DEFERRED, NULL);

  and then in a tight loop try to lock a mutex and call test cancel like:
  while (pthread_mutex_trylock (&progress_lock) ==
                                 EBUSY)
                                  pthread_testcancel ();

  if the thread is exited because the parent thread sent a pthread_exit
  (NULL); for instance, you will see that error.

  gcc thinks that this file is in:
  $> gcc --print-file-name=libgcc_s.so.1
  /lib/../lib/libgcc_s.so.1

  and not /lib/libgcc_s.so.1. though the path should really point to the
  same file in the end.

  This error is fixed by adding /lib to /etc/ld.so.conf and running
  ldconfig

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