[Boost-users] question on boost::interprocess

Subject: [Boost-users] question on boost::interprocess
From: Markos.Perrakis_at_[hidden]
Date: 2008-10-22 16:21:10

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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