CPP-924 Pure virtual function called when Session object is being destructed (#483)

Created a smart pointer owning version of `Callback` to ensure that `Cluster`
lives as long as `PrepareHostHandler`.

Author: mpenick

src/callback.hpp

@@ -19,6 +19,7 @@
 
 #include "aligned_storage.hpp"
 #include "macros.hpp"
+#include "ref_counted.hpp"
 
 #include <new>
 #include <stddef.h>
@@ -41,6 +42,14 @@ class Callback {
     STATIC_ASSERT(ALIGN_OF(Storage) >= ALIGN_OF(MemberInvoker));
   }
 
+  template <class F, class T>
+  Callback(F func, SharedRefPtr<T> ptr)
+      : invoker_(new (&storage_) MemberPtrInvoker<F, T>(func, ptr)) {
+    typedef MemberInvoker<F, T> MemberPtrInvoker;
+    STATIC_ASSERT(sizeof(Storage) >= sizeof(MemberPtrInvoker));
+    STATIC_ASSERT(ALIGN_OF(Storage) >= ALIGN_OF(MemberPtrInvoker));
+  }
+
   template <class F>
   explicit Callback(F func)
       : invoker_(new (&storage_) FunctionInvoker<F>(func)) {
@@ -96,6 +105,20 @@ class Callback {
     T* object;
   };
 
+  template <class F, class T>
+  struct MemberPtrInvoker : public Invoker {
+    MemberPtrInvoker(F func, const SharedRefPtr<T>& ptr)
+        : func(func)
+        , ptr(ptr) {}
+
+    R invoke(const Arg& arg) const { return (ptr.get()->*func)(arg); }
+
+    Invoker* copy(Storage* storage) { return new (storage) MemberPtrInvoker<F, T>(func, ptr); }
+
+    F func;
+    SharedRefPtr<T> ptr;
+  };
+
   template <class F>
   struct FunctionInvoker : public Invoker {
     FunctionInvoker(F func)
@@ -134,6 +157,11 @@ Callback<R, Arg> bind_callback(R (T::*func)(Arg), T* object) {
   return Callback<R, Arg>(func, object);
 }
 
+template <class R, class Arg, class T>
+Callback<R, Arg> bind_callback(R (T::*func)(Arg), const SharedRefPtr<T>& ptr) {
+  return Callback<R, Arg>(func, ptr);
+}
+
 template <class R, class Arg>
 Callback<R, Arg> bind_callback(R (*func)(Arg)) {
   return Callback<R, Arg>(func);

src/cluster.cpp

@@ -504,7 +504,7 @@ void Cluster::internal_notify_host_up(const Address& address) {
     return; // Ignore host
   }
 
-  if (!prepare_host(host, bind_callback(&Cluster::on_prepare_host_up, this))) {
+  if (!prepare_host(host, bind_callback(&Cluster::on_prepare_host_up, Cluster::Ptr(this)))) {
     notify_host_up_after_prepare(host);
   }
 }
@@ -597,7 +597,7 @@ void Cluster::notify_host_add(const Host::Ptr& host) {
     return; // Ignore host
   }
 
-  if (!prepare_host(host, bind_callback(&Cluster::on_prepare_host_add, this))) {
+  if (!prepare_host(host, bind_callback(&Cluster::on_prepare_host_add, Cluster::Ptr(this)))) {
     notify_host_add_after_prepare(host);
   }
 }