Merge some features from gerbert into OwnPtr and RetainPtr.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/1203c327c71

AK/OwnPtr.h

@@ -1,7 +1,7 @@
 #pragma once
 
-#include <cstddef>
-#include <utility>
+#include "StdLib.h"
+#include "Types.h"
 
 namespace AK {
 
@@ -12,8 +12,17 @@ public:
     explicit OwnPtr(T* ptr) : m_ptr(ptr) { }
     OwnPtr(OwnPtr&& other) : m_ptr(other.leakPtr()) { }
     template<typename U> OwnPtr(OwnPtr<U>&& other) : m_ptr(static_cast<T*>(other.leakPtr())) { }
-    ~OwnPtr() { clear(); }
     OwnPtr(std::nullptr_t) { };
+    ~OwnPtr()
+    {
+        clear();
+#ifdef SANITIZE_PTRS
+        if constexpr(sizeof(T*) == 8)
+            m_ptr = (T*)(0xe1e1e1e1e1e1e1e1);
+        else
+            m_ptr = (T*)(0xe1e1e1e1);
+#endif
+    }
 
     OwnPtr& operator=(OwnPtr&& other)
     {
@@ -84,7 +93,7 @@ private:
 template<class T, class... Args> inline OwnPtr<T>
 make(Args&&... args)
 {
-    return OwnPtr<T>(new T(std::forward<Args>(args)...));
+    return OwnPtr<T>(new T(forward<Args>(args)...));
 }
 
 }

AK/RetainPtr.h

@@ -1,8 +1,6 @@
 #pragma once
 
-namespace std {
-typedef decltype(nullptr) nullptr_t;
-}
+#include "Types.h"
 
 namespace AK {
 
@@ -32,7 +30,16 @@ public:
     RetainPtr(AdoptTag, T& object) : m_ptr(&object) { }
     RetainPtr(RetainPtr&& other) : m_ptr(other.leakRef()) { }
     template<typename U> RetainPtr(RetainPtr<U>&& other) : m_ptr(static_cast<T*>(other.leakRef())) { }
-    ~RetainPtr() { clear(); }
+    ~RetainPtr()
+    {
+        clear();
+#ifdef SANITIZE_PTRS
+        if constexpr(sizeof(T*) == 8)
+            m_ptr = (T*)(0xe0e0e0e0e0e0e0e0);
+        else
+            m_ptr = (T*)(0xe0e0e0e0);
+#endif
+    }
     RetainPtr(std::nullptr_t) { }
 
     RetainPtr& operator=(RetainPtr&& other)

AK/StdLib.h

@@ -30,9 +30,31 @@ T&& move(T& arg)
     return static_cast<T&&>(arg);
 }
 
+template<typename T>
+struct identity {
+    typedef T type;
+};
+template<typename T>
+T&& forward(typename identity<T>::type&& param)
+{
+    return static_cast<typename identity<T>::type&&>(param);
+}
+
+template<typename T, typename U>
+T exchange(T& a, U&& b)
+{
+    T tmp = move(a);
+    a = move(b);
+    return tmp;
+}
+
+
 }
 
 using AK::min;
 using AK::max;
+using AK::move;
+using AK::forward;
+using AK::exchange;
 using AK::ceilDiv;