Hi there, If I connect a signal to a slot (functor or lambda), and the signal is then run, it calls the slot. What if the slot now has code that causes the signal to destruct? Will this "self-destruct" the slot (functor or lambda), by calling it's destructor BEFORE the slot-call has finished executing??? This would be a disaster! But it seems like is is safe. It seems: Even if the signal is destructed (from it's own slot-call), the slot destructor does not yet get called, until the slot-call has finished. Which would be safe. (Code example below) But is this really the case? Is this always safe? (If so: how does this roughly work?) Thanks. ///////////////////////////////////////////////////////////////////// #include <iostream> #include <string> #include #include <functional> #include <map> using namespace std; using FuncSig = void(); class BaseWrapper { public: BaseWrapper() { cout << "BaseWrapper() " << ++mm[""] << endl; } BaseWrapper(const string &n) : name{n} { cout << "BaseWrapper() " << name << ' ' << ++mm[name] << endl; } BaseWrapper(const BaseWrapper &other) : name{other.name} { cout << "BaseWrapper(const BaseWrapper &other) " << name << ' ' << ++mm[name] << endl; } virtual ~BaseWrapper() { cout << "~BaseWrapper() " << name << ' ' << mm[name]-- << endl; } private: static map mm; // static counter const string name; }; map BaseWrapper::mm; class MySig : BaseWrapper, public boost::signals2::signal<FuncSig> { }; using Sig = MySig; //boost::signals2::signal<FuncSig>; class A { public: A() {} boost::signals2::connection add_listener(const string &str, const Sig::slot_type &slot) { //my_map.emplace(str, Sig{}); auto x = my_map.emplace(std::piecewise_construct, std::forward_as_tuple(str), std::forward_as_tuple()); return x.first->second.connect(slot); } void remove_listener(const string &str) { auto it = my_map.find(str); if (it != my_map.cend()) { my_map.erase(it); } } void call(const string &str) { auto it = my_map.find(str); if (it != my_map.cend()) { it->second(); } } private: map my_map; }; class Functor : BaseWrapper { public: Functor(A *a_, int x_) : BaseWrapper{"Functor"}, a{a_}, x{x_} {} void operator()() const { cout << " this == " << this << endl; cout << " x == " << x << endl; a->remove_listener("hello"); cout << " this == " << this << endl; cout << " x == " << x << endl; } private: A *a; int x; }; int main() { A a; { Functor fun{&a, 4}; a.add_listener("hello", fun); } a.call("hello"); std::cout << "end" << endl; return 0; } /////////////////////////////////////////////////////////////////////