[Boost-bugs] [Boost C++ Libraries] #12489: file_lock and fstream read causes "permission denied"

Subject: [Boost-bugs] [Boost C++ Libraries] #12489: file_lock and fstream read causes "permission denied"
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-09-28 09:34:18

#12489: file_lock and fstream read causes "permission denied"
------------------------------+--------------------------
 Reporter:  anonymous         |      Owner:  igaztanaga
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  interprocess
  Version:  Boost 1.61.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+--------------------------
 The following code causes an exception in the std::getline. The error
 message received by strerror() is "permission denied".

 The exception goes away by removing the lock and unlock line.

 This issue is related to to https://svn.boost.org/trac/boost/ticket/2796

 which focuses on writing to the filelock. A "workaround" for that issue is
 to unlock before flushing the stream. It is not an option to read file
 before locking it.

 How can this issue be fixed? Any possible workaround?

 #include "stdafx.h"

 #include <iostream>

 #include <fstream>

 #include <boost/interprocess/sync/file_lock.hpp>

 int main(int argc, char* argv[])

 {
   std::fstream stream("lock", std::fstream::in | std::fstream::out);

   stream.exceptions(std::fstream::badbit | std::fstream::failbit);

   boost::interprocess::file_lock lock("lock");

   lock.lock();

   std::string content;
   try
   {
     std::getline(stream, content);
   }
   catch (std::exception)
   {
     auto desc = strerror(errno);
   }

   std::cout << content << std::endl;

   lock.unlock();

   stream.close();

   return 0;
 }

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12489>
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