Sorry for the spam.  I got the answer, how to do it. Ignore my previous mail. [quote] #include #include <iostream> using namespace std; class A {     public:     void hello () { cout << "Hello, friends...!" << endl; } }; typedef boost::shared_ptr<A> APtr; void* callbk (void* o) {     APtr a = *static_cast(o);     a->hello(); } int main() { A* rawPtr = new A; boost::shared_ptr<A>sPtr(rawPtr); callbk((void*)&sPtr); return 0; } [/quote] warm regars, RV ________________________________ From: Mupparthy Ravindranath To: "boost-users@lists.boost.org" Sent: Tuesday, 10 May 2011 1:26 PM Subject: How to cast a boost::shared_ptr to void* Hi all, My requirement is to cast an object of type shared_ptr as void*, so that I can send it to a callback function that accepts a void*.  I cannot change callback the function signature because it is part of an existing legacy code. In the existing code, I am sending a raw object pointer (instead of shared_ptr).  Now, if I want to pass a shared_ptr, it won't compile because I cannot cast the shared ptr to void*.  Can anyone suggest some workaround for this.  I tried searching the mailing lists and internet, but not much luck. regards, RV