Merge pull request #1455 from yuriks/ResultVal-union

core: Use unrestricted union to hold storage of ResultVal value

src/core/hle/result.h

@@ -269,7 +269,6 @@ public:
         : result_code(error_code)
     {
         ASSERT(error_code.IsError());
-        UpdateDebugPtr();
     }
 
     /**
@@ -287,40 +286,37 @@ public:
         : result_code(o.result_code)
     {
         if (!o.empty()) {
-            new (&storage) T(*o.GetPointer());
+            new (&object) T(o.object);
         }
-        UpdateDebugPtr();
     }
 
     ResultVal(ResultVal&& o)
         : result_code(o.result_code)
     {
         if (!o.empty()) {
-            new (&storage) T(std::move(*o.GetPointer()));
+            new (&object) T(std::move(o.object));
         }
-        UpdateDebugPtr();
     }
 
     ~ResultVal() {
         if (!empty()) {
-            GetPointer()->~T();
+            object.~T();
         }
     }
 
     ResultVal& operator=(const ResultVal& o) {
         if (!empty()) {
             if (!o.empty()) {
-                *GetPointer() = *o.GetPointer();
+                object = o.object;
             } else {
-                GetPointer()->~T();
+                object.~T();
             }
         } else {
             if (!o.empty()) {
-                new (&storage) T(*o.GetPointer());
+                new (&object) T(o.object);
             }
         }
         result_code = o.result_code;
-        UpdateDebugPtr();
 
         return *this;
     }
@@ -333,11 +329,10 @@ public:
     void emplace(ResultCode success_code, Args&&... args) {
         ASSERT(success_code.IsSuccess());
         if (!empty()) {
-            GetPointer()->~T();
+            object.~T();
         }
-        new (&storage) T(std::forward<Args>(args)...);
+        new (&object) T(std::forward<Args>(args)...);
         result_code = success_code;
-        UpdateDebugPtr();
     }
 
     /// Returns true if the `ResultVal` contains an error code and no value.
@@ -350,15 +345,15 @@ public:
 
     ResultCode Code() const { return result_code; }
 
-    const T& operator* () const { return *GetPointer(); }
-          T& operator* ()       { return *GetPointer(); }
-    const T* operator->() const { return  GetPointer(); }
-          T* operator->()       { return  GetPointer(); }
+    const T& operator* () const { return object; }
+          T& operator* ()       { return object; }
+    const T* operator->() const { return &object; }
+          T* operator->()       { return &object; }
 
     /// Returns the value contained in this `ResultVal`, or the supplied default if it is missing.
     template <typename U>
     T ValueOr(U&& value) const {
-        return !empty() ? *GetPointer() : std::move(value);
+        return !empty() ? object : std::move(value);
     }
 
     /// Asserts that the result succeeded and returns a reference to it.
@@ -372,31 +367,10 @@ public:
     }
 
 private:
-    typedef typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type StorageType;
-
-    StorageType storage;
+    // A union is used to allocate the storage for the value, while allowing us to construct and
+    // destruct it at will.
+    union { T object; };
     ResultCode result_code;
-#ifdef _DEBUG
-    // The purpose of this pointer is to aid inspecting the type with a debugger, eliminating the
-    // need to cast `storage` to a pointer or pay attention to `result_code`.
-    const T* debug_ptr;
-#endif
-
-    void UpdateDebugPtr() {
-#ifdef _DEBUG
-        debug_ptr = empty() ? nullptr : static_cast<const T*>(static_cast<const void*>(&storage));
-#endif
-    }
-
-    const T* GetPointer() const {
-        ASSERT(!empty());
-        return static_cast<const T*>(static_cast<const void*>(&storage));
-    }
-
-    T* GetPointer() {
-        ASSERT(!empty());
-        return static_cast<T*>(static_cast<void*>(&storage));
-    }
 };
 
 /**