G++ does not like "non-template functions as friends of class templates. So I change the operator== into member function. :-|

src/wrapper.hh

@@ -29,9 +29,16 @@ public:
     ~Wrapper();
 
     Wrapper<T> copy() const;
-
-    friend
-    bool operator==(const Wrapper<T>& a, const Wrapper<T>& b);
+    
+    bool operator==(const Wrapper<T>& b) const
+    {
+        return value==b.value;
+    }
+    
+    bool operator!=(const Wrapper<T>& b) const
+    {
+        return value!=b.value;
+    }
 
 private:
     // must be defined for each wrapped type:
@@ -78,11 +85,18 @@ public:
         _free(value);
     }
     
+    bool operator==(const Wrapper<T*>& b) const
+    {
+        return value==b.value;
+    }
+    
+    bool operator!=(const Wrapper<T*>& b) const
+    {
+        return value!=b.value;
+    }
+    
     const T* get() const { return value; }
     T*  move_out()       { T* r = value; value=nullptr; return r;}
-    
-    friend
-    bool operator==(const Wrapper<T*>& a, const Wrapper<T*>& b);
 
 protected:
 
@@ -97,12 +111,6 @@ protected:
     T* value;
 };
 
-template<class T>
-inline
-bool operator!=(const Wrapper<T>& a, const Wrapper<T>& b)
-{
-    return !(a==b);
-}
 
 
 // Wraps single-linked lists and provides an interface compatible