I have created a shared memory segment with the boost::interprocess library and have created and populated a boost::interprocess::map in that segment.  The key for the map is the boost::interprocess::string class.

If I want to search for an element in the map I obviously have to supply the key for the element. Here is what I do:

{
        std::string key;
        // assign here a value to key string object

        const Char_Alloc char_alloc( (shared_memory_segment_obj.get_segment_manager() ) );
        boost::interprocess::string some_string( char_alloc );

        some_string.assign( key.c_str() );
}

where Char_Alloc is a suitable shared memory allocator for plain characters.

As you can see from the code the key (the some_string object) for the map is created in local memory (in-process memory) but the contents of the string are allocated in shared memory.

If two threads access this shared memory segment and execute the above code at the same time, is this thread safe? Will the two concurrent assign() statements use the same location in shared memory and cause overlaps? Or is the shared memory allocator smart enough to synchronize the two assign() calls and execute them sequencially?

In case the shared memory allocator is not smart enough to guarantee synchronization can I use a boost::interprocess mutex for thread synchronization?


Regards,
Markos Perrakis


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