Revert "slot, signal: Avoid compiler warnings from function pointer conversions"

kjellahl · kjellahl · commit efe4089f7dec · 2018-07-16T13:18:31.000+02:00
This reverts commit c6262e0. This can be done in a better way by keeping the union in a template function.
diff --git a/sigc++/functors/macros/slot.h.m4 b/sigc++/functors/macros/slot.h.m4
@@ -63,17 +63,7 @@ FOR(1, $1,[
   inline T_return operator()(LOOP(arg%1_type_ _A_a%1, $1)) const
     {
       if (!empty() && !blocked())
-      {
-        // Conversion between different types of function pointers with
-        // reinterpret_cast can make gcc8 print a warning.
-        // https://github.com/libsigcplusplus/libsigcplusplus/issues/1
-        union {
-          internal::hook ph;
-          call_type pc;
-        } u;
-        u.ph = slot_base::rep_->call_;
-        return (u.pc)(LIST(slot_base::rep_, LOOP(_A_a%1, $1)));
-      }
+        return (reinterpret_cast<call_type>(slot_base::rep_->call_))(LIST(slot_base::rep_, LOOP(_A_a%1, $1)));
       return T_return();
     }
 
@@ -365,14 +355,7 @@ ifelse($1,0,[
    * @return A function pointer formed from call_it().
    */
   static hook address()
-  {
-    union {
-      hook ph;
-      decltype(&call_it) pc;
-    } u;
-    u.pc = &call_it;
-    return u.ph;
-  }
+    { return reinterpret_cast<hook>(&call_it); }
 };
 
 ])
@@ -500,14 +483,7 @@ struct slot_call
    * @return A function pointer formed from call_it().
    */
   static hook address()
-  {
-    union {
-      hook ph;
-      decltype(&call_it) pc;
-    } u;
-    u.pc = &call_it;
-    return u.ph;
-  }
+    { return reinterpret_cast<hook>(&call_it); }
 };
 
 /** Abstracts functor execution.
@@ -539,14 +515,7 @@ struct slot_call<T_functor, T_return>
    * @return A function pointer formed from call_it().
    */
   static hook address()
-  {
-    union {
-      hook ph;
-      decltype(&call_it) pc;
-    } u;
-    u.pc = &call_it;
-    return u.ph;
-  }
+    { return reinterpret_cast<hook>(&call_it); }
 };
 
 } /* namespace internal */
@@ -606,14 +575,7 @@ public:
   inline T_return operator()(type_trait_take_t<T_arg>... _A_a) const
     {
       if (!empty() && !blocked())
-      {
-        union {
-          internal::hook ph;
-          call_type pc;
-        } u;
-        u.ph = slot_base::rep_->call_;
-        return (u.pc)(slot_base::rep_, _A_a...);
-      }
+        return (reinterpret_cast<call_type>(slot_base::rep_->call_))(slot_base::rep_, _A_a...);
       return T_return();
     }
 
diff --git a/sigc++/macros/signal.h.m4 b/sigc++/macros/signal.h.m4
@@ -51,17 +51,7 @@ ifelse($1,0,[dnl
    * @return The slot's return value.
    */
   T_return operator()(const slot_type& _A_slot) const
-  {
-    // Conversion between different types of function pointers with
-    // reinterpret_cast can make gcc8 print a warning.
-    // https://github.com/libsigcplusplus/libsigcplusplus/issues/1
-    union {
-      internal::hook ph;
-      typename slot_type::call_type pc;
-    } u;
-    u.ph = _A_slot.rep_->call_;
-    return (u.pc)(LIST(_A_slot.rep_, LOOP(_A_a%1_, $1)));
-  }
+    { return (reinterpret_cast<typename slot_type::call_type>(_A_slot.rep_->call_))(LIST(_A_slot.rep_, LOOP(_A_a%1_, $1))); }
 dnl  T_return operator()(const slot_type& _A_slot) const
 dnl    { return _A_slot(LOOP(_A_a%1_, $1)); }
 
@@ -160,19 +150,13 @@ FOR(1, $1,[
         if (it == slots.end())
           return T_return(); // note that 'T_return r_();' doesn't work => define 'r_' after this line and initialize as follows:
   
-        union {
-          internal::hook ph;
-          call_type pc;
-        } u;
-        u.ph = it->rep_->call_;
-        r_ = (u.pc)(LIST(it->rep_, LOOP(_A_a%1, $1)));
+        r_ = (reinterpret_cast<call_type>(it->rep_->call_))(LIST(it->rep_, LOOP(_A_a%1, $1)));
         for (++it; it != slots.end(); ++it)
-        {
-          if (it->empty() || it->blocked())
-            continue;
-          u.ph = it->rep_->call_;
-          r_ = (u.pc)(LIST(it->rep_, LOOP(_A_a%1, $1)));
-        }
+          {
+            if (it->empty() || it->blocked())
+              continue;
+            r_ = (reinterpret_cast<call_type>(it->rep_->call_))(LIST(it->rep_, LOOP(_A_a%1, $1)));
+          }
       }
       
       return r_;
@@ -217,19 +201,13 @@ FOR(1, $1,[
         if (it == reverse_iterator_type(slots.begin()))
           return T_return(); // note that 'T_return r_();' doesn't work => define 'r_' after this line and initialize as follows:
   
-        union {
-          internal::hook ph;
-          call_type pc;
-        } u;
-        u.ph = it->rep_->call_;
-        r_ = (u.pc)(LIST(it->rep_, LOOP(_A_a%1, $1)));
+        r_ = (reinterpret_cast<call_type>(it->rep_->call_))(LIST(it->rep_, LOOP(_A_a%1, $1)));
         for (++it; it != reverse_iterator_type(slots.begin()); ++it)
-        {
-          if (it->empty() || it->blocked())
-            continue;
-          u.ph = it->rep_->call_;
-          r_ = (u.pc)(LIST(it->rep_, LOOP(_A_a%1, $1)));
-        }
+          {
+            if (it->empty() || it->blocked())
+              continue;
+            r_ = (reinterpret_cast<call_type>(it->rep_->call_))(LIST(it->rep_, LOOP(_A_a%1, $1)));
+          }
       }
       
       return r_;
@@ -265,17 +243,12 @@ FOR(1, $1,[
       signal_exec exec(impl);
       temp_slot_list slots(impl->slots_);
 
-      union {
-        internal::hook ph;
-        call_type pc;
-      } u;
       for (const auto& slot : slots)
-      {
-        if (slot.empty() || slot.blocked())
-          continue;
-        u.ph = slot.rep_->call_;
-        (u.pc)(LIST(slot.rep_, LOOP(_A_a%1, $1)));
-      }
+        {
+          if (slot.empty() || slot.blocked())
+            continue;
+          (reinterpret_cast<call_type>(slot.rep_->call_))(LIST(slot.rep_, LOOP(_A_a%1, $1)));
+        }
     }
 
 _DEPRECATE_IFDEF_START
@@ -301,17 +274,12 @@ FOR(1, $1,[
       typedef std::reverse_iterator<signal_impl::iterator_type, std::random_access_iterator_tag,
                                      slot_base, slot_base&, slot_base*, std::ptrdiff_t> reverse_iterator_type;
 #endif
-      union {
-        internal::hook ph;
-        call_type pc;
-      } u;
       for (auto it = reverse_iterator_type(slots.end()); it != reverse_iterator_type(slots.begin()); ++it)
-      {
-        if (it->empty() || it->blocked())
-          continue;
-        u.ph = it->rep_->call_;
-        (u.pc)(LIST(it->rep_, LOOP(_A_a%1, $1)));
-      }
+        {
+          if (it->empty() || it->blocked())
+            continue;
+          (reinterpret_cast<call_type>(it->rep_->call_))(LIST(it->rep_, LOOP(_A_a%1, $1)));
+        }
     }
 _DEPRECATE_IFDEF_END
 };
