Hi, I am running the program below (Vista with boost 1.43, mingw/gcc 4.5.1). I would expect slot.x to be 5 but it is zero. Why boost::signal creates another instance of the slot object ? What am I missing here ? Thank you in advance for your attention, Mau. ---------------------------------------------------------------- #include <iostream> #include <boost/signal.hpp> struct S { int x; S (): x(0) {} void operator () (int i) { std::cout << "&slot1 = " << this << std::endl; x = i; std::cout << "slot1.x = " << this->x << std::endl; } }; int main () { S slot; boost::signal<void (int)> sig; std::cout << "&slot2 = " << &slot << std::endl; sig.connect (slot); sig (5); std::cout << "slot2.x = " << slot.x << std::endl; return 0; } -------------------------------------------------------------------- Output: &slot2 = 0x22fee4 &slot1 = 0x341448 slot1.x = 5 slot2.x = 0