From a4609655535148e5e8766737125175fba0d19358
From: Kjell Ahlstedt <kjell.ahlstedt@bredband.net>
Date: Mon, 13 Feb 2017 19:00:41 +0100
Subject: [PATCH] slot_rep: Make destructor, destroy() and dup() virtual

* sigc++/functors/slot_base.h:
* sigc++/functors/slot.h: Make ~slot_rep(), slot_rep::destroy() and
slot_rep::dup() virtual. Bug 777618
---

Cebtenzzre: Modified patch to apply to a much older version of libsigc++.

diff -Naur a/sigc++/functors/slot_base.cc b/sigc++/functors/slot_base.cc
--- a/sigc++/functors/slot_base.cc	2019-01-19 22:40:31.602141215 -0500
+++ b/sigc++/functors/slot_base.cc	2019-01-19 22:41:18.853321720 -0500
@@ -41,8 +41,14 @@
 class dummy_slot_rep : public sigc::internal::slot_rep
 {
 public:
-  dummy_slot_rep() : slot_rep(nullptr, nullptr, &clone) {}
-  static void* clone(void*) { return new dummy_slot_rep(); }
+  dummy_slot_rep() : slot_rep(nullptr) {}
+
+  void destroy() override
+  {
+    call_ = nullptr;
+  }
+  
+  slot_rep* dup() const override { return new dummy_slot_rep(); }
 };
 } // anonymous namespace
 
diff -Naur a/sigc++/functors/slot_base.h b/sigc++/functors/slot_base.h
--- a/sigc++/functors/slot_base.h	2019-01-19 22:40:31.602141215 -0500
+++ b/sigc++/functors/slot_base.h	2019-01-19 22:41:18.856655137 -0500
@@ -71,28 +71,17 @@
    */
   hook call_;
 
-  /// Callback that detaches the slot_rep object from referred trackables and destroys it.
-  /* This could be a replaced by a virtual dtor. However since this struct is
-   * crucual for the efficiency of the whole library we want to avoid this.
-   */
-  hook destroy_;
-
-  /** Callback that makes a deep copy of the slot_rep object.
-   * @return A deep copy of the slot_rep object.
-   */
-  hook dup_;
-
   /** Callback of parent_. */
   hook cleanup_;
 
   /** Parent object whose callback cleanup_ is executed on notification. */
   void* parent_;
 
-  inline slot_rep(hook call__, hook destroy__, hook dup__) noexcept
-    : call_(call__), destroy_(destroy__), dup_(dup__), cleanup_(nullptr), parent_(nullptr) {}
+  inline slot_rep(hook call__) noexcept
+    : call_(call__), cleanup_(nullptr), parent_(nullptr) {}
 
-  inline ~slot_rep()
-    { destroy(); }
+  virtual ~slot_rep()
+    {}
 
   // only MSVC needs this to guarantee that all new/delete are executed from the DLL module
 #ifdef SIGC_NEW_DELETE_IN_LIBRARY_ONLY
@@ -102,14 +91,12 @@
 
   /** Destroys the slot_rep object (but doesn't delete it).
    */
-  inline void destroy()
-    { if (destroy_) (*destroy_)(this); }
+  virtual void destroy() = 0;
 
   /** Makes a deep copy of the slot_rep object.
    * @return A deep copy of the slot_rep object.
    */
-  inline slot_rep* dup() const
-    { return reinterpret_cast<slot_rep*>((*dup_)(const_cast<slot_rep*>(this))); }
+  virtual slot_rep* dup() const = 0;
 
   /** Set the parent with a callback.
    * slots have one parent exclusively.
diff -Naur a/sigc++/functors/slot.h b/sigc++/functors/slot.h
--- a/sigc++/functors/slot.h	2019-01-19 22:40:31.602141215 -0500
+++ b/sigc++/functors/slot.h	2019-01-20 15:35:47.152759393 -0500
@@ -50,54 +50,53 @@
 template <class T_functor>
 struct typed_slot_rep : public slot_rep
 {
-  typedef typed_slot_rep<T_functor> self;
-
   /* Use an adaptor type so that arguments can be passed as const references
    * through explicit template instantiation from slot_call#::call_it() */
   typedef typename adaptor_trait<T_functor>::adaptor_type adaptor_type;
 
   /** The functor contained by this slot_rep object. */
-  adaptor_type functor_;
+  adaptor_type *functor_;
 
   /** Constructs an invalid typed slot_rep object.
    * The notification callback is registered using visit_each().
    * @param functor The functor contained by the new slot_rep object.
    */
   inline typed_slot_rep(const T_functor& functor)
-    : slot_rep(nullptr, &destroy, &dup), functor_(functor)
-    { sigc::visit_each_type<trackable*>(slot_do_bind(this), functor_); }
+    : slot_rep(nullptr), functor_(new adaptor_type(functor))
+    { sigc::visit_each_type<trackable*>(slot_do_bind(this), *functor_); }
 
   inline typed_slot_rep(const typed_slot_rep& cl)
-    : slot_rep(cl.call_, &destroy, &dup), functor_(cl.functor_)
-    { sigc::visit_each_type<trackable*>(slot_do_bind(this), functor_); }
+    : slot_rep(cl.call_), functor_(new adaptor_type(*cl.functor_))
+    { sigc::visit_each_type<trackable*>(slot_do_bind(this), *functor_); }
 
   typed_slot_rep& operator=(const typed_slot_rep& src) = delete;
 
   typed_slot_rep(typed_slot_rep&& src) = delete;
   typed_slot_rep& operator=(typed_slot_rep&& src) = delete;
 
-  inline ~typed_slot_rep()
+  ~typed_slot_rep() override
     {
-      call_ = nullptr;
-      destroy_ = nullptr;
-      sigc::visit_each_type<trackable*>(slot_do_unbind(this), functor_);
+      // Call destroy() non-virtually.
+      // It's unwise to make virtual calls in a constructor or destructor.
+      typed_slot_rep::destroy();
     }
 
   /** Detaches the stored functor from the other referred trackables and destroys it.
    * This does not destroy the base slot_rep object.
    */
-  static void* destroy(void* data)
+  void destroy() override
     {
-      self* self_ = static_cast<self*>(reinterpret_cast<slot_rep*>(data));
-      self_->call_ = nullptr;
-      self_->destroy_ = nullptr;
-      sigc::visit_each_type<trackable*>(slot_do_unbind(self_), self_->functor_);
-      self_->functor_.~adaptor_type();
+      call_ = nullptr;
+      if (functor_)
+      {
+        sigc::visit_each_type<trackable*>(slot_do_unbind(this), *functor_);
+        delete functor_;
+        functor_ = nullptr;
+      }
       /* don't call disconnect() here: destroy() is either called
        * a) from the parent itself (in which case disconnect() leads to a segfault) or
        * b) from a parentless slot (in which case disconnect() does nothing)
        */
-      return nullptr;
     }
 
   /** Makes a deep copy of the slot_rep object.
@@ -105,11 +104,8 @@
    * slot_rep object is registered in the referred trackables.
    * @return A deep copy of the slot_rep object.
    */
-  static void* dup(void* data)
-    {
-      slot_rep* a_rep = reinterpret_cast<slot_rep*>(data);
-      return static_cast<slot_rep*>(new self(*static_cast<self*>(a_rep)));
-    }
+  slot_rep* dup() const override
+  { return new typed_slot_rep(*this); }
 };
 
 /** Abstracts functor execution.
@@ -133,7 +129,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_)();
+      return (*typed_rep->functor_)();
     }
 
   /** Forms a function pointer from call_it().
@@ -166,7 +162,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>>
                (a_1);
     }
 
@@ -202,7 +198,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>>
                (a_1, a_2);
     }
 
@@ -240,7 +236,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>>
                (a_1, a_2, a_3);
     }
 
@@ -280,7 +276,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>>
                (a_1, a_2, a_3, a_4);
     }
 
@@ -322,7 +318,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>>
                (a_1, a_2, a_3, a_4, a_5);
     }
 
@@ -366,7 +362,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>, type_trait_take_t<T_arg6>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>, type_trait_take_t<T_arg6>>
                (a_1, a_2, a_3, a_4, a_5, a_6);
     }
 
@@ -412,7 +408,7 @@
     {
       typedef typed_slot_rep<T_functor> typed_slot;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>, type_trait_take_t<T_arg6>, type_trait_take_t<T_arg7>>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg1>, type_trait_take_t<T_arg2>, type_trait_take_t<T_arg3>, type_trait_take_t<T_arg4>, type_trait_take_t<T_arg5>, type_trait_take_t<T_arg6>, type_trait_take_t<T_arg7>>
                (a_1, a_2, a_3, a_4, a_5, a_6, a_7);
     }
 
@@ -447,7 +443,7 @@
     {
       using typed_slot = typed_slot_rep<T_functor>;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_).SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg>...>
+      return (typed_rep->functor_)->SIGC_WORKAROUND_OPERATOR_PARENTHESES<type_trait_take_t<T_arg>...>
                (a_...);
     }
 
@@ -480,7 +476,7 @@
     {
       using typed_slot = typed_slot_rep<T_functor>;
       typed_slot *typed_rep = static_cast<typed_slot*>(rep);
-      return (typed_rep->functor_)();
+      return (*typed_rep->functor_)();
     }
 
   /** Forms a function pointer from call_it().