move thunk into its own header

Reviewed By: vitaut

Differential Revision: D27036041

fbshipit-source-id: 038b35b9690f17b59425c13c57176ac7dd017ea5

folly/Memory.h

@@ -34,6 +34,7 @@
 #include <folly/functional/Invoke.h>
 #include <folly/lang/Align.h>
 #include <folly/lang/Exception.h>
+#include <folly/lang/Thunk.h>
 #include <folly/memory/Malloc.h>
 #include <folly/portability/Config.h>
 #include <folly/portability/Malloc.h>

folly/Utility.h

@@ -415,39 +415,4 @@ T declval() noexcept;
 #define FOLLY_DECLVAL(...) ::folly::detail::declval<__VA_ARGS__>()
 #endif
 
-namespace detail {
-
-//  thunk
-//
-//  A carefully curated collection of generic general-purpose thunk templates:
-//  * make: operator new with given arguments
-//  * ruin: operator delete
-//  * ctor: in-place constructor with given arguments
-//  * dtor: in-place destructor
-//  * noop: no-op function with the given arguments
-struct thunk {
-  template <typename T, typename... A>
-  static void* make(A... a) {
-    return new T(static_cast<A>(a)...);
-  }
-  template <typename T>
-  static void ruin(void* const ptr) noexcept {
-    delete static_cast<T*>(ptr);
-  }
-
-  template <typename T, typename... A>
-  static void ctor(void* const ptr, A... a) {
-    ::new (ptr) T(static_cast<A>(a)...);
-  }
-  template <typename T>
-  static void dtor(void* const ptr) noexcept {
-    static_cast<T*>(ptr)->~T();
-  }
-
-  template <typename... T>
-  static void noop(T...) noexcept {}
-};
-
-} // namespace detail
-
 } // namespace folly

folly/detail/StaticSingletonManager.h

@@ -24,6 +24,7 @@
 #include <folly/Likely.h>
 #include <folly/Utility.h>
 #include <folly/detail/Singleton.h>
+#include <folly/lang/Thunk.h>
 #include <folly/lang/TypeInfo.h>
 
 namespace folly {

folly/io/async/EventBaseLocal.h

@@ -27,6 +27,7 @@
 #include <folly/Likely.h>
 #include <folly/Synchronized.h>
 #include <folly/io/async/EventBase.h>
+#include <folly/lang/Thunk.h>
 
 namespace folly {
 

folly/lang/Thunk.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+namespace folly {
+namespace detail {
+
+//  thunk
+//
+//  A carefully curated collection of generic general-purpose thunk templates:
+//  * make: operator new with given arguments
+//  * ruin: operator delete
+//  * ctor: in-place constructor with given arguments
+//  * dtor: in-place destructor
+//  * noop: no-op function with the given arguments
+struct thunk {
+  template <typename T, typename... A>
+  static void* make(A... a) {
+    return new T(static_cast<A>(a)...);
+  }
+  template <typename T>
+  static void ruin(void* const ptr) noexcept {
+    delete static_cast<T*>(ptr);
+  }
+
+  template <typename T, typename... A>
+  static void ctor(void* const ptr, A... a) {
+    ::new (ptr) T(static_cast<A>(a)...);
+  }
+  template <typename T>
+  static void dtor(void* const ptr) noexcept {
+    static_cast<T*>(ptr)->~T();
+  }
+
+  template <typename... T>
+  static void noop(T...) noexcept {}
+};
+
+} // namespace detail
+} // namespace folly