Merge pull request #4441 from Dechcaudron/15341

Fixes issue 15341

Author: andralex

std/signals.d

@@ -153,21 +153,31 @@ mixin template Signal(T1...)
      */
     final void disconnect(slot_t slot)
     {
-        debug (signal) writefln("Signal.disconnect(slot)");
+        size_t disconnectedSlots = 0;
+        size_t instancePreviousSlots = 0;
+
         for (size_t i = 0; i < slots_idx; )
         {
-            if (slots[i] == slot)
-            {   slots_idx--;
+            if (slots[i].ptr == slot.ptr &&
+                ++instancePreviousSlots &&
+                slots[i] == slot)
+            {
+                slots_idx--;
+                disconnectedSlots++;
                 slots[i] = slots[slots_idx];
                 slots[slots_idx] = null;        // not strictly necessary
-
-                Object o = _d_toObject(slot.ptr);
-                rt_detachDisposeEvent(o, &unhook);
             }
             else
                 i++;
         }
-    }
+
+         // detach object from dispose event if all its slots have been removed
+        if (instancePreviousSlots == disconnectedSlots)
+        {
+            Object o = _d_toObject(slot.ptr);
+            rt_detachDisposeEvent(o, &unhook);
+        }
+     }
 
     /* **
      * Special function called when o is destroyed.
@@ -555,6 +565,34 @@ void linkin() { }
     a.value6 = 46;
 }
 
+// Triggers bug from issue 15341
+unittest
+{
+    class Observer
+    {
+       void watch() { }
+       void watch2() { }
+    }
+
+    class Bar
+    {
+       mixin Signal!();
+    }
+
+   auto a = new Bar;
+   auto o = new Observer;
+
+   //Connect both observer methods for the same instance
+   a.connect(&o.watch);
+   a.connect(&o.watch2); // not connecting watch2() or disconnecting it manually fixes the issue
+
+   //Disconnect a single method of the two
+   a.disconnect(&o.watch); // NOT disconnecting watch() fixes the issue
+
+   destroy(o); // destroying o should automatically call unhook and disconnect the slot for watch2
+   a.emit(); // should not raise segfault since &o.watch2 is no longer connected
+}
+
 version(none) // Disabled because of dmd @@@BUG5028@@@
 @system unittest
 {