Question

I had a problem with some of my code with the following function calls:

User::User(const Socket::SocketAddress& addr) {
    address = addr;
    _usersListBySession.insert(std::pair<uint32_t, std::shared_ptr<User>>(sessionID, std::shared_ptr<User>(this)));
    assert(this->address == addr); // succeeds
    _userListByAddress.insert(std::pair<Socket::SocketAddress, std::shared_ptr<User>>(addr, std::shared_ptr<User>(this)));
    assert(this->address == addr); // fails
}

I fixed the issue by doing this:

User::User(const Socket::SocketAddress& addr) {
    address = addr;
    std::shared_ptr<User> user(this);
    _usersListBySession.insert(std::pair<uint32_t, std::shared_ptr<User>>(sessionID, user));
    assert(this->address == addr); // succeeds
    _userListByAddress.insert(std::pair<Socket::SocketAddress, std::shared_ptr<User>>(addr, user));
    assert(this->address == addr); // succeeds
}

What did I do and why does it work?

Answer 1

In your first example, you assign this to two different std::shared_ptrs, resulting in a double delete.

In your second example, you assign this to one std::shared_ptr user, which gets ref-counted properly, when you give it as a parameter to insert.