Move the type_traits portability header into its own portability header

Summary: Split up the big, all-inclusive Portability header a bit

Reviewed By: yfeldblum

Differential Revision: D3723253

fbshipit-source-id: a91c38775825626f3c13853ac8168daa078a169a

folly/Makefile.am

@@ -296,6 +296,7 @@ nobase_follyinclude_HEADERS = \
 	portability/SysTypes.h \
 	portability/SysUio.h \
 	portability/Time.h \
+	portability/TypeTraits.h \
 	portability/Windows.h \
 	portability/Unistd.h \
 	Preprocessor.h \

folly/Portability.h

@@ -245,28 +245,6 @@ namespace std { typedef ::max_align_t max_align_t; }
 #include <folly/detail/FunctionalExcept.h>
 #endif
 
-#if defined(__cplusplus)
-// Unfortunately, boost::has_trivial_copy<T> is broken in libc++ due to its
-// usage of __has_trivial_copy(), so we can't use it as a
-// least-common-denominator for C++11 implementations that don't support
-// std::is_trivially_copyable<T>.
-//
-//      http://stackoverflow.com/questions/12754886/has-trivial-copy-behaves-differently-in-clang-and-gcc-whos-right
-//
-// As a result, use std::is_trivially_copyable() where it exists, and fall back
-// to Boost otherwise.
-#if FOLLY_HAVE_STD__IS_TRIVIALLY_COPYABLE
-#include <type_traits>
-#define FOLLY_IS_TRIVIALLY_COPYABLE(T)                   \
-  (std::is_trivially_copyable<T>::value)
-#else
-#include <boost/type_traits.hpp>
-#define FOLLY_IS_TRIVIALLY_COPYABLE(T)                   \
-  (boost::has_trivial_copy<T>::value &&                  \
-   boost::has_trivial_destructor<T>::value)
-#endif
-#endif // __cplusplus
-
 // MSVC specific defines
 // mainly for posix compat
 #ifdef _MSC_VER

folly/experimental/LockFreeRingBuffer.h

@@ -24,8 +24,9 @@
 #include <string.h>
 #include <type_traits>
 
-#include <folly/detail/TurnSequencer.h>
 #include <folly/Portability.h>
+#include <folly/detail/TurnSequencer.h>
+#include <folly/portability/TypeTraits.h>
 #include <folly/portability/Unistd.h>
 
 namespace folly {

folly/portability/TypeTraits.h

+/*
+ * Copyright 2016 Facebook, Inc.
+ *
+ * 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
+
+// Unfortunately, boost::has_trivial_copy<T> is broken in libc++ due to its
+// usage of __has_trivial_copy(), so we can't use it as a
+// least-common-denominator for C++11 implementations that don't support
+// std::is_trivially_copyable<T>.
+//
+//      http://stackoverflow.com/questions/12754886/has-trivial-copy-behaves-differently-in-clang-and-gcc-whos-right
+//
+// As a result, use std::is_trivially_copyable() where it exists, and fall back
+// to Boost otherwise.
+#if FOLLY_HAVE_STD__IS_TRIVIALLY_COPYABLE
+#include <type_traits>
+#define FOLLY_IS_TRIVIALLY_COPYABLE(T) (std::is_trivially_copyable<T>::value)
+#else
+#include <boost/type_traits.hpp>
+#define FOLLY_IS_TRIVIALLY_COPYABLE(T) \
+  (boost::has_trivial_copy<T>::value && boost::has_trivial_destructor<T>::value)
+#endif

folly/small_vector.h

@@ -49,6 +49,7 @@
 #include <folly/SmallLocks.h>
 #include <folly/portability/Constexpr.h>
 #include <folly/portability/Malloc.h>
+#include <folly/portability/TypeTraits.h>
 
 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
 #pragma GCC diagnostic push

folly/test/small_vector_test.cpp

@@ -28,6 +28,7 @@
 #include <gtest/gtest.h>
 
 #include <folly/Conv.h>
+#include <folly/portability/TypeTraits.h>
 
 using folly::small_vector;
 using namespace folly::small_vector_policy;