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

Subject: Re: [Boost-users] Segmentation fault when using std::string in stl::maps in shared memory
From: hamsinv (hamsinv_at_[hidden])
Date: 2008-10-20 02:38:05

Hello All,

After a few search I found out that we cannot use std::string. Instead we
should try with interprocess::basic_string. Can anyone guide me through
this.

hamsinv wrote:
> 
> 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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