/usr/include/boost/interprocess/sync/ is in libboost1.65-dev 1.65.1+dfsg-0ubuntu5.
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..
/usr/include/boost/interprocess/sync/detail/
/usr/include/boost/interprocess/sync/detail/common_algorithms.hpp
/usr/include/boost/interprocess/sync/detail/condition_algorithm_8a.hpp
/usr/include/boost/interprocess/sync/detail/condition_any_algorithm.hpp
/usr/include/boost/interprocess/sync/detail/locks.hpp
/usr/include/boost/interprocess/sync/file_lock.hpp
/usr/include/boost/interprocess/sync/interprocess_condition.hpp
/usr/include/boost/interprocess/sync/interprocess_condition_any.hpp
/usr/include/boost/interprocess/sync/interprocess_mutex.hpp
/usr/include/boost/interprocess/sync/interprocess_recursive_mutex.hpp
/usr/include/boost/interprocess/sync/interprocess_semaphore.hpp
/usr/include/boost/interprocess/sync/interprocess_sharable_mutex.hpp
/usr/include/boost/interprocess/sync/interprocess_upgradable_mutex.hpp
/usr/include/boost/interprocess/sync/lock_options.hpp
/usr/include/boost/interprocess/sync/mutex_family.hpp
/usr/include/boost/interprocess/sync/named_condition.hpp
/usr/include/boost/interprocess/sync/named_condition_any.hpp
/usr/include/boost/interprocess/sync/named_mutex.hpp
/usr/include/boost/interprocess/sync/named_recursive_mutex.hpp
/usr/include/boost/interprocess/sync/named_semaphore.hpp
/usr/include/boost/interprocess/sync/named_sharable_mutex.hpp
/usr/include/boost/interprocess/sync/named_upgradable_mutex.hpp
/usr/include/boost/interprocess/sync/null_mutex.hpp
/usr/include/boost/interprocess/sync/posix/
/usr/include/boost/interprocess/sync/posix/condition.hpp
/usr/include/boost/interprocess/sync/posix/mutex.hpp
/usr/include/boost/interprocess/sync/posix/named_mutex.hpp
/usr/include/boost/interprocess/sync/posix/named_semaphore.hpp
/usr/include/boost/interprocess/sync/posix/pthread_helpers.hpp
/usr/include/boost/interprocess/sync/posix/ptime_to_timespec.hpp
/usr/include/boost/interprocess/sync/posix/recursive_mutex.hpp
/usr/include/boost/interprocess/sync/posix/semaphore.hpp
/usr/include/boost/interprocess/sync/posix/semaphore_wrapper.hpp
/usr/include/boost/interprocess/sync/scoped_lock.hpp
/usr/include/boost/interprocess/sync/sharable_lock.hpp
/usr/include/boost/interprocess/sync/shm/
/usr/include/boost/interprocess/sync/shm/named_condition.hpp
/usr/include/boost/interprocess/sync/shm/named_condition_any.hpp
/usr/include/boost/interprocess/sync/shm/named_creation_functor.hpp
/usr/include/boost/interprocess/sync/shm/named_mutex.hpp
/usr/include/boost/interprocess/sync/shm/named_recursive_mutex.hpp
/usr/include/boost/interprocess/sync/shm/named_semaphore.hpp
/usr/include/boost/interprocess/sync/shm/named_upgradable_mutex.hpp
/usr/include/boost/interprocess/sync/spin/
/usr/include/boost/interprocess/sync/spin/condition.hpp
/usr/include/boost/interprocess/sync/spin/interprocess_barrier.hpp
/usr/include/boost/interprocess/sync/spin/mutex.hpp
/usr/include/boost/interprocess/sync/spin/recursive_mutex.hpp
/usr/include/boost/interprocess/sync/spin/semaphore.hpp
/usr/include/boost/interprocess/sync/spin/wait.hpp
/usr/include/boost/interprocess/sync/upgradable_lock.hpp
/usr/include/boost/interprocess/sync/windows/
/usr/include/boost/interprocess/sync/windows/condition.hpp
/usr/include/boost/interprocess/sync/windows/mutex.hpp
/usr/include/boost/interprocess/sync/windows/named_condition.hpp
/usr/include/boost/interprocess/sync/windows/named_condition_any.hpp
/usr/include/boost/interprocess/sync/windows/named_mutex.hpp
/usr/include/boost/interprocess/sync/windows/named_recursive_mutex.hpp
/usr/include/boost/interprocess/sync/windows/named_semaphore.hpp
/usr/include/boost/interprocess/sync/windows/named_sync.hpp
/usr/include/boost/interprocess/sync/windows/recursive_mutex.hpp
/usr/include/boost/interprocess/sync/windows/semaphore.hpp
/usr/include/boost/interprocess/sync/windows/sync_utils.hpp
/usr/include/boost/interprocess/sync/windows/winapi_mutex_wrapper.hpp
/usr/include/boost/interprocess/sync/windows/winapi_semaphore_wrapper.hpp
/usr/include/boost/interprocess/sync/windows/winapi_wrapper_common.hpp