[Boost-users] Segmentation fault when using std::string in stl::maps in shared memory

Subject: [Boost-users] Segmentation fault when using std::string in stl::maps in shared memory
From: hamsinv (hamsinv_at_[hidden])
Date: 2008-10-20 00:30:24

Hello All,

I have been trying boost library for sharing stl::maps using shared memory.
I am able to run the example code on sharing stl::maps successfully. It uses
int-float pair to store in map. I have to store std::string-int pair.
Writing into the map, works fine, yet reading the same from a different
process results in Segmentation fault.

Both the Process are as follows:
Process1.cpp
---------------------
//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2007. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#include <iostream.h>
#include "boost/interprocess/detail/config_begin.hpp"
#include "boost/interprocess/detail/workaround.hpp"
//[doc_map
#include "boost/interprocess/managed_shared_memory.hpp"
#include "boost/interprocess/containers/map.hpp"
#include "boost/interprocess/allocators/allocator.hpp"
#include <functional>
#include <utility>
int main ()
{
   using namespace boost::interprocess;
   shared_memory_object::remove("MySharedMemory");
   try{
      managed_shared_memory segment
         (create_only
         ,"MySharedMemory" //segment name
         ,65536);          //segment size in bytes

      typedef int    KeyType;
      typedef std::string  MappedType;
      typedef std::pair<const int, std::string> ValueType;
      typedef allocator<ValueType, managed_shared_memory::segment_manager>
         ShmemAllocator;
      typedef map<KeyType, MappedType, std::less<KeyType>, ShmemAllocator>
MyMap;
     ShmemAllocator alloc_inst (segment.get_segment_manager());
 MyMap *mymap =
         segment.construct<MyMap>("MyMap")      //object name
                                    (std::less<int>() //first  ctor
parameter
                                    ,alloc_inst);     //second ctor
parameter

      //Insert data in the map
      for(int i = 0; i < 10; ++i){
        cout<<"I value is: "<<i<<endl;
         mymap->insert(std::pair<const int,std::string>(i,"Hello"));
      }
     mymap = segment.find<MyMap>("MyMap").first;
      cout<<"Shared memory map created"<< mymap<<endl;
        for( MyMap::iterator it = mymap->begin();it != mymap->end();++it)
        {
                 cout<<"key: "<<(*it).first<<"  Value:
"<<(*it).second<<endl;
        }
   }
   catch(...){
      shared_memory_object::remove("MySharedMemory");
      throw;
   }
   return 0;
}

Process2.cpp
--------------------
//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2007. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#include <iostream.h>
#include "boost/interprocess/detail/config_begin.hpp"
#include "boost/interprocess/detail/workaround.hpp"
//[doc_map
#include "boost/interprocess/managed_shared_memory.hpp"
#include "boost/interprocess/containers/map.hpp"
#include "boost/interprocess/allocators/allocator.hpp"
#include <functional>
#include <utility>
int main ()
{
   using namespace boost::interprocess;

   try{
      managed_shared_memory segment
         (open_only
         ,"MySharedMemory" //segment name
         );
      typedef int    KeyType;
      typedef std::string  MappedType;
      typedef std::pair<const int, std::string> ValueType;
     typedef allocator<ValueType, managed_shared_memory::segment_manager>
         ShmemAllocator;
      typedef map<KeyType, MappedType, std::less<KeyType>, ShmemAllocator>
MyMap;
 MyMap *mymap =
         segment.find<MyMap>("MyMap").first;      //object name
     for( MyMap::iterator it = mymap->begin();it != mymap->end();++it)
        {
                 cout<<"key: "<<(*it).first<<"  Value:
"<<(*it).second<<endl;
        }
   }
   catch(...){
      shared_memory_object::remove("MySharedMemory");
      throw;
   }
   return 0;
}

Could anyone please tell me what's going wrong and how can i use std::string
as key and int as value.

Thank you.
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