Is boost::interprocess::shared_ptr threadsafe (and interprocess-safe)?

Question

I want to share data between threads, and have it automatically deleted when the last user is done with it. This seems to work, most of the time, using boost::interpro

Answer 1

Looking through the code in shared_ptr.hpp, and at the docs on the boost website, it would seem as though dereferencing a single instance may or may not be threadsafe depending on the second template parameter, which determines the internal pointer type to be used. Specifically, "The internal pointer will be of the same pointer type as typename VoidAllocator::pointer type (that is, if typename VoidAllocator::pointer is offset_ptr, the internal pointer will be offset_ptr)." And since dereferences merely return the result of get()/get_pointer() method of this class, it should probably depend entirely on that. Boost::shared_ptr will work if you want simultaneous read-only access. For write access from multiple threads, you might have to write your own wrapper modelled after offset_ptr.