Hi, I am having some troubles with serialization of shared_ptrs. The basic problem is that when I serialize a shared_ptr, then later deserialize into a new shared_ptr, the use_count of the new pointer is, incorrectly (as far as I can see), 2 rather than 1. I am using boost 1.33.1 and gcc 4.0.1. Here is some example code to demonstrate the problem: ----- // compile with: // gcc -o ptrser-test ptrser-test.cpp -lstdc++ -lboost_serialization-gcc #include <iostream> #include <fstream> #include #include #include using namespace std; using namespace boost; class Item { public: // Constructors/destructor-------------------------- Item(int n = 0) : _n(n) { cout << "In Item constructor" << endl; }; Item(const Item& other) { cout << "In Item copy constructor" << endl; _n = other._n; }; ~Item() { cout << "In Item destructor" << endl; }; // Data members------------------------------------- int _n; // Methods------------------------------------------ friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & _n; } }; class Bag { public: // Constructors/destructor-------------------------- Bag() { cout << "In Bag default constructor" << endl; }; Bag(shared_ptr<Item> item) : _item(item) { cout << "In Bag shared_ptr constructor" << endl; }; Bag(const Bag& other) { cout << "In Bag copy constructor" << endl; _item = other._item; }; ~Bag() { cout << "In Bag destructor" << endl; }; // Data members------------------------------------- shared_ptr<Item> _item; // Methods------------------------------------------ void printUseCount() const { cout << "Use count: " << _item.use_count() << endl; } friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & _item; } }; int main(int argc, char **argv) { const char *filename = "bag.ser"; // create a Bag object with a new Item in it Bag *pBag = new Bag(shared_ptr<Item>(new Item(1))); // now serialize the Bag cout << "About to serialize bag..." << endl; ofstream osSer(filename); boost::archive::text_oarchive oa(osSer); const Bag& constBag = *pBag; oa << constBag; osSer.close(); pBag->printUseCount(); // delete the original Bag cout << "About to delete bag 1..." << endl; delete pBag; // create a new Bag object cout << "About to create a new bag..." << endl; pBag = new Bag; pBag->printUseCount(); // and deserialize it into the new Bag object cout << "About to deserialize bag..." << endl; ifstream isSer(filename, std::ios::binary); boost::archive::text_iarchive ia(isSer); ia >> *pBag; isSer.close(); pBag->printUseCount(); // delete the second BSag cout << "About to delete bag 2..." << endl; delete pBag; return 0; } ----- This code produces the following output: ----- In Item constructor In Bag shared_ptr constructor About to serialize bag... Use count: 1 About to delete bag 1... In Bag destructor In Item destructor About to create a new bag... In Bag default constructor Use count: 0 About to deserialize bag... In Item constructor Use count: 2 About to delete bag 2... In Bag destructor In Item destructor ----- The series of constructor and destructor calls is as expected. After the first Bag object is created with a shared_ptr to an Item in it, the use_count of the shared_ptr is 1. When the first Bag object (including the shared_ptr) are deleted, and a new, empty Bag object created, the use_count is now (as expected) 0. However, when the serialization archive is deserialized into the new Bag object, the use_count of the shared_ptr jumps from 0 to 2. Am I doing something silly here, or is this a bug in the shared_ptr serialization code? For interest, the saved archive (bag.ser) produced by this code looks like this: ----- 22 serialization::archive 3 0 0 0 1 2 1 0 0 1 ----- Any help would be much appreciated. Tim