id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
12489,"file_lock and fstream read causes ""permission denied""",anonymous,Ion Gaztañaga,"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;
}
",Bugs,new,To Be Determined,interprocess,Boost 1.61.0,Problem,,,