variable_watch: Add a deleter for the client data

The client data is arbitrary and the callback may be called an
unspecified number of times, so the cmVariableWatch must be the one to
delete the client data in the end (if it is needed at all).

1 files changed, 11 insertions, 2 deletions

diff --git a/Source/cmVariableWatch.h b/Source/cmVariableWatch.h
index 45273e5ae2..d666815982 100644
--- a/Source/cmVariableWatch.h
+++ b/Source/cmVariableWatch.h
@@ -26,6 +26,7 @@ class cmVariableWatch
 public:
   typedef void (*WatchMethod)(const std::string& variable, int access_type,
     void* client_data, const char* newValue, const cmMakefile* mf);
+  typedef void (*DeleteData)(void* client_data);
 
   cmVariableWatch();
   ~cmVariableWatch();
@@ -34,7 +35,7 @@ public:
    * Add watch to the variable
    */
   void AddWatch(const std::string& variable, WatchMethod method,
-                void* client_data=0);
+                void* client_data=0, DeleteData delete_data=0);
   void RemoveWatch(const std::string& variable, WatchMethod method);
 
   /**
@@ -67,7 +68,15 @@ protected:
   {
     WatchMethod Method;
     void*        ClientData;
-    Pair() : Method(0), ClientData(0) {}
+    DeleteData   DeleteDataCall;
+    Pair() : Method(0), ClientData(0), DeleteDataCall(0) {}
+    ~Pair()
+      {
+      if (this->DeleteDataCall && this->ClientData)
+        {
+        this->DeleteDataCall(this->ClientData);
+        }
+      }
   };
 
   typedef std::vector< Pair* > VectorOfPairs;