I tried a lot of things and it all comes down to the question below. First I'll give an overview about what I want to do. First some typedefs and then the class that should be written to the shared_memory: typedef boost::interprocess::managed_shared_memory::segment_manager segment_manager_t; typedef boost::interprocess::allocator<void, segment_manager_t> void_allocator; typedef boost::interprocess::allocator<char, segment_manager_t> char_allocator; typedef boost::interprocess::basic_string<char, std::char_traits<char>, char_allocator> char_string; class A { A(const void_allocator &void_alloc); : str("", void_alloc) {}; char_string str; //... other datatypes ... }; const void_allocator * _void_alloc = _managed_shm->get_segment_manager(); ObjectType * pointer; One object of class A is now written to shared_mem via: template<typename ObjectType> void createObjWithAllocator(ObjectType & obj) { pointer = _managed_shm->construct<ObjectType>(boost::interprocess::unique_instance)(*_void_alloc); }; The real communication is something like this. And here is the real problem: template <typename ObjectType> void write_object(ObjectType & data) { (*pointer) = data; }; The problem now is that I cannot instantiate an object of class A without an Allocator void_allocator. So the final question of all my posts before is, if (and how) I can create an void_allocator that allocates memory from the heap and not from the shared_mem that fits the declaration of void_allocator. Any hints? Thanks in advance Best regards, Mortz