[Bug libstdc++/57975] Core dump caused by linking with -lpthread

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57975

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It only "works" without -lpthread because the implementation of
pthread_mutex_lock() in libc.so is a no-op, so your program is a busy loop that
spins using 100% CPU, not waiting patiently on the condvar.

When you link to libpthread you get a real implementation of pthread_mutex_lock
that fails because when you call condvar.wait(lock) you fail to meet the
precondition that lock.owns_lock() is true, so it's undefined behaviour.