[Boost-bugs] [Boost C++ Libraries] #12620: Make boost::unique_lock::unlock respect BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED

Subject: [Boost-bugs] [Boost C++ Libraries] #12620: Make boost::unique_lock::unlock respect BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-11-23 20:48:04

#12620: Make boost::unique_lock::unlock respect
BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED
-------------------------------------------------+-------------------------
 Reporter:  Alexandre Pereira Nunes              |      Owner:  anthonyw
  <alexandre.nunes@…>                            |     Status:  new
     Type:  Bugs                                 |  Component:  thread
Milestone:  To Be Determined                     |   Severity:  Problem
  Version:  Boost 1.62.0                         |
 Keywords:                                       |
-------------------------------------------------+-------------------------
 For a C++11 conformant g++ with working C++11 threads, the following code
 works if LIB is defined to std and throws if defined to boost::

 #define LIB boost

 LIB::mutex mtx;
 LIB::unique_lock<LIB::mutex> l(mtx, LIB::defer_lock);
 LIB::condition_variable cnd;
 cnd.wait(l, []{ /*whatever*/ return true;}); // this throws.

 The attached patch makes boost::unique_lock::unlock respect
 BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED and not require the lock
 to be held (if you'll ever have only one thread waiting on a condition
 variable it seems that the mutex is useless as there's no race involved,
 c++11 threads at least when backed by pthread seems to follow that
 behavior).

 Even with this patch, boost *will* lock the mutex on exit - I didn't
 attempt to change that (as my code copes with that), but c++11 seems to
 avoid touching the mutex or correctly leaves it as it once was.

 I'm not sure what/if any of this behavior is standardized or
 implementation dependent, but it seems more coherent to respect
 BOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED - specially the common
 case where it's not defined.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12620>
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