[Boost-bugs] [Boost C++ Libraries] #8536: Repeated shared_mutex.unlock_shared() can underflow

Subject: [Boost-bugs] [Boost C++ Libraries] #8536: Repeated shared_mutex.unlock_shared() can underflow
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-05-01 17:27:35

#8536: Repeated shared_mutex.unlock_shared() can underflow
-----------------------------------------------+----------------------------
 Reporter:  Zack Moratto <zmoratto@…>          |       Owner:  anthonyw
     Type:  Bugs                               |      Status:  new     
Milestone:  To Be Determined                   |   Component:  thread  
  Version:  Boost 1.53.0                       |    Severity:  Problem 
 Keywords:  shared, mutex, underflow           |  
-----------------------------------------------+----------------------------
 Boost 1.53's shared_mutex can underflow if the user calls unlock_shared
 twice or right after construction.

 shared_mutex m();[[BR]]
 m.unlock_shared();

 The problem is specifically this line which can be found inside
 boost/thread/pthread/shared_mutex.hpp. ''(should be line 148)''

 {{{
             bool const last_reader=!--state.shared_count;
 }}}

 It doesn't check that state.shared_count is nonzero before decrementing.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8536>
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