/*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#pragma once
-#include <memory>
+#include <functional>
#include <limits>
+#include <memory>
#include <type_traits>
-#include <functional>
#include <folly/Portability.h>
#include <bits/c++config.h>
#endif
-#include <boost/type_traits.hpp>
-
#define FOLLY_CREATE_HAS_MEMBER_TYPE_TRAITS(classname, type_name) \
template <typename TTheClass_> \
struct classname##__folly_traits_impl__ { \
template <typename UTheClass_> \
- static std::true_type test(typename UTheClass_::type_name*); \
+ static constexpr bool test(typename UTheClass_::type_name*) { \
+ return true; \
+ } \
template <typename> \
- static std::false_type test(...); \
+ static constexpr bool test(...) { \
+ return false; \
+ } \
}; \
template <typename TTheClass_> \
- using classname = decltype( \
+ using classname = typename std::conditional< \
classname##__folly_traits_impl__<TTheClass_>::template test<TTheClass_>( \
- nullptr))
+ nullptr), \
+ std::true_type, \
+ std::false_type>::type;
#define FOLLY_CREATE_HAS_MEMBER_FN_TRAITS_IMPL(classname, func_name, cv_qual) \
template <typename TTheClass_, typename RTheReturn_, typename... TTheArgs_> \
namespace folly {
+/***
+ * _t
+ *
+ * Instead of:
+ *
+ * using decayed = typename std::decay<T>::type;
+ *
+ * With the C++14 standard trait aliases, we could use:
+ *
+ * using decayed = std::decay_t<T>;
+ *
+ * Without them, we could use:
+ *
+ * using decayed = _t<std::decay<T>>;
+ *
+ * Also useful for any other library with template types having dependent
+ * member types named `type`, like the standard trait types.
+ */
+template <typename T>
+using _t = typename T::type;
+
+/**
+ * type_t
+ *
+ * A type alias for the first template type argument. `type_t` is useful for
+ * controlling class-template and function-template partial specialization.
+ *
+ * Example:
+ *
+ * template <typename Value>
+ * class Container {
+ * public:
+ * template <typename... Args>
+ * Container(
+ * type_t<in_place_t, decltype(Value(std::declval<Args>()...))>,
+ * Args&&...);
+ * };
+ *
+ * void_t
+ *
+ * A type alias for `void`. `void_t` is useful for controling class-template
+ * and function-template partial specialization.
+ *
+ * Example:
+ *
+ * // has_value_type<T>::value is true if T has a nested type `value_type`
+ * template <class T, class = void>
+ * struct has_value_type
+ * : std::false_type {};
+ *
+ * template <class T>
+ * struct has_value_type<T, folly::void_t<typename T::value_type>>
+ * : std::true_type {};
+ */
+
+/**
+ * There is a bug in libstdc++, libc++, and MSVC's STL that causes it to
+ * ignore unused template parameter arguments in template aliases and does not
+ * cause substitution failures. This defect has been recorded here:
+ * http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1558.
+ *
+ * This causes the implementation of std::void_t to be buggy, as it is likely
+ * defined as something like the following:
+ *
+ * template <typename...>
+ * using void_t = void;
+ *
+ * This causes the compiler to ignore all the template arguments and does not
+ * help when one wants to cause substitution failures. Rather declarations
+ * which have void_t in orthogonal specializations are treated as the same.
+ * For example, assuming the possible `T` types are only allowed to have
+ * either the alias `one` or `two` and never both or none:
+ *
+ * template <typename T,
+ * typename std::void_t<std::decay_t<T>::one>* = nullptr>
+ * void foo(T&&) {}
+ * template <typename T,
+ * typename std::void_t<std::decay_t<T>::two>* = nullptr>
+ * void foo(T&&) {}
+ *
+ * The second foo() will be a redefinition because it conflicts with the first
+ * one; void_t does not cause substitution failures - the template types are
+ * just ignored.
+ */
+
+namespace traits_detail {
+template <class T, class...>
+struct type_t_ {
+ using type = T;
+};
+} // namespace traits_detail
+
+template <class T, class... Ts>
+using type_t = typename traits_detail::type_t_<T, Ts...>::type;
+template <class... Ts>
+using void_t = type_t<void, Ts...>;
+
/**
* IsRelocatable<T>::value describes the ability of moving around
* memory a value of type T by using memcpy (as opposed to the
template <class T>
using is_trivially_copyable = std::is_trivially_copyable<T>;
#endif
-}
+} // namespace traits_detail
struct Ignore {
+ Ignore() = default;
template <class T>
- /* implicit */ Ignore(const T&) {}
+ constexpr /* implicit */ Ignore(const T&) {}
template <class T>
const Ignore& operator=(T const&) const { return *this; }
};
decltype(std::declval<T>() == std::declval<U>()),
bool
> {};
-}
+} // namespace traits_detail_IsEqualityComparable
/* using override */ using traits_detail_IsEqualityComparable::
IsEqualityComparable;
decltype(std::declval<T>() < std::declval<U>()),
bool
> {};
-}
+} // namespace traits_detail_IsLessThanComparable
/* using override */ using traits_detail_IsLessThanComparable::
IsLessThanComparable;
namespace traits_detail_IsNothrowSwappable {
-#if defined(_MSC_VER) || defined(__cpp_lib_is_swappable)
-// MSVC already implements the C++17 P0185R1 proposal which
-// adds std::is_nothrow_swappable, so use it instead.
+#if defined(__cpp_lib_is_swappable) || (_CPPLIB_VER && _HAS_CXX17)
+// MSVC 2015+ already implements the C++17 P0185R1 proposal which
+// adds std::is_nothrow_swappable, so use it instead if C++17 mode
+// is enabled.
template <typename T>
using IsNothrowSwappable = std::is_nothrow_swappable<T>;
+#elif _CPPLIB_VER
+// MSVC 2015+ defines the base even if C++17 is disabled, and
+// MSVC 2015 has issues with our fallback implementation due to
+// over-eager evaluation of noexcept.
+template <typename T>
+using IsNothrowSwappable = std::_Is_nothrow_swappable<T>;
#else
/* using override */ using std::swap;
noexcept(swap(std::declval<T&>(), std::declval<T&>()))
> {};
#endif
-}
+} // namespace traits_detail_IsNothrowSwappable
/* using override */ using traits_detail_IsNothrowSwappable::IsNothrowSwappable;
// Lighter-weight than Conjunction, but evaluates all sub-conditions eagerly.
template <class... Ts>
-using StrictConjunction =
- std::is_same<Bools<Ts::value..., true>, Bools<true, Ts::value...>>;
+struct StrictConjunction
+ : std::is_same<Bools<Ts::value...>, Bools<(Ts::value || true)...>> {};
+
+template <class... Ts>
+struct StrictDisjunction
+ : Negation<
+ std::is_same<Bools<Ts::value...>, Bools<(Ts::value && false)...>>
+ > {};
} // namespace folly
* regular type, use it like this:
*
* // Make sure you're at namespace ::folly scope
- * template<> FOLLY_ASSUME_RELOCATABLE(MyType)
+ * template <> FOLLY_ASSUME_RELOCATABLE(MyType)
*
* When using it with a template type, use it like this:
*
* // Make sure you're at namespace ::folly scope
- * template<class T1, class T2>
+ * template <class T1, class T2>
* FOLLY_ASSUME_RELOCATABLE(MyType<T1, T2>)
*/
#define FOLLY_ASSUME_RELOCATABLE(...) \
struct IsRelocatable< __VA_ARGS__ > : std::true_type {};
/**
- * Use this macro ONLY inside namespace boost. When using it with a
- * regular type, use it like this:
- *
- * // Make sure you're at namespace ::boost scope
- * template<> FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(MyType)
- *
- * When using it with a template type, use it like this:
- *
- * // Make sure you're at namespace ::boost scope
- * template<class T1, class T2>
- * FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(MyType<T1, T2>)
- */
-#define FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(...) \
- struct has_nothrow_constructor< __VA_ARGS__ > : ::boost::true_type {};
-
-/**
- * The FOLLY_ASSUME_FBVECTOR_COMPATIBLE* macros below encode two
- * assumptions: first, that the type is relocatable per IsRelocatable
- * above, and that it has a nothrow constructor. Most types can be
- * assumed to satisfy both conditions, but it is the responsibility of
- * the user to state that assumption. User-defined classes will not
- * work with fbvector (see FBVector.h) unless they state this
- * combination of properties.
+ * The FOLLY_ASSUME_FBVECTOR_COMPATIBLE* macros below encode the
+ * assumption that the type is relocatable per IsRelocatable
+ * above. Many types can be assumed to satisfy this condition, but
+ * it is the responsibility of the user to state that assumption.
+ * User-defined classes will not be optimized for use with
+ * fbvector (see FBVector.h) unless they state that assumption.
*
* Use FOLLY_ASSUME_FBVECTOR_COMPATIBLE with regular types like this:
*
*/
// Use this macro ONLY at global level (no namespace)
-#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE(...) \
- namespace folly { template<> FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__) } \
- namespace boost { \
- template<> FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(__VA_ARGS__) }
+#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE(...) \
+ namespace folly { \
+ template <> \
+ FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__) \
+ }
// Use this macro ONLY at global level (no namespace)
-#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(...) \
- namespace folly { \
- template <class T1> FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1>) } \
- namespace boost { \
- template <class T1> FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(__VA_ARGS__<T1>) }
+#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(...) \
+ namespace folly { \
+ template <class T1> \
+ FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1>) \
+ }
// Use this macro ONLY at global level (no namespace)
-#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(...) \
- namespace folly { \
- template <class T1, class T2> \
- FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2>) } \
- namespace boost { \
- template <class T1, class T2> \
- FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(__VA_ARGS__<T1, T2>) }
+#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(...) \
+ namespace folly { \
+ template <class T1, class T2> \
+ FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2>) \
+ }
// Use this macro ONLY at global level (no namespace)
-#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_3(...) \
- namespace folly { \
- template <class T1, class T2, class T3> \
- FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2, T3>) } \
- namespace boost { \
- template <class T1, class T2, class T3> \
- FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(__VA_ARGS__<T1, T2, T3>) }
+#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_3(...) \
+ namespace folly { \
+ template <class T1, class T2, class T3> \
+ FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2, T3>) \
+ }
// Use this macro ONLY at global level (no namespace)
-#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_4(...) \
- namespace folly { \
- template <class T1, class T2, class T3, class T4> \
- FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2, T3, T4>) } \
- namespace boost { \
- template <class T1, class T2, class T3, class T4> \
- FOLLY_ASSUME_HAS_NOTHROW_CONSTRUCTOR(__VA_ARGS__<T1, T2, T3, T4>) }
+#define FOLLY_ASSUME_FBVECTOR_COMPATIBLE_4(...) \
+ namespace folly { \
+ template <class T1, class T2, class T3, class T4> \
+ FOLLY_ASSUME_RELOCATABLE(__VA_ARGS__<T1, T2, T3, T4>) \
+ }
/**
* Instantiate FOLLY_ASSUME_FBVECTOR_COMPATIBLE for a few types. It is
FOLLY_NAMESPACE_STD_END
-namespace boost {
-
-template <class T> class shared_ptr;
-
-template <class T, class U>
-struct has_nothrow_constructor< std::pair<T, U> >
- : std::integral_constant<bool,
- has_nothrow_constructor<T>::value &&
- has_nothrow_constructor<U>::value> {};
-
-} // namespace boost
-
namespace folly {
// STL commonly-used types
IsRelocatable<U>::value> {};
// Is T one of T1, T2, ..., Tn?
-template <class T, class... Ts>
-struct IsOneOf {
- enum { value = false };
-};
-
-template <class T, class T1, class... Ts>
-struct IsOneOf<T, T1, Ts...> {
- enum { value = std::is_same<T, T1>::value || IsOneOf<T, Ts...>::value };
-};
+template <typename T, typename... Ts>
+using IsOneOf = StrictDisjunction<std::is_same<T, Ts>...>;
/*
* Complementary type traits for integral comparisons.
// types) that violate -Wsign-compare and/or -Wbool-compare so suppress them
// in order to not prevent all calling code from using it.
FOLLY_PUSH_WARNING
-FOLLY_GCC_DISABLE_WARNING(sign-compare)
+FOLLY_GCC_DISABLE_WARNING("-Wsign-compare")
#if __GNUC_PREREQ(5, 0)
-FOLLY_GCC_DISABLE_WARNING(bool-compare)
+FOLLY_GCC_DISABLE_WARNING("-Wbool-compare")
#endif
FOLLY_MSVC_DISABLE_WARNING(4388) // sign-compare
FOLLY_MSVC_DISABLE_WARNING(4804) // bool-compare
FOLLY_POP_WARNING
-} // namespace detail {
+} // namespace detail
// same as `x < 0`
template <typename T>
RHS, rhs, typename std::remove_reference<LHS>::type
>(lhs);
}
-
-namespace traits_detail {
-struct InPlaceTag {};
-template <class>
-struct InPlaceTypeTag {};
-template <std::size_t>
-struct InPlaceIndexTag {};
-}
-
-/**
- * Like std::piecewise_construct, a tag type & instance used for in-place
- * construction of non-movable contained types, e.g. by Synchronized.
- * Follows the naming and design of std::in_place suggested in
- * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0032r2.pdf
- */
-using in_place_t = traits_detail::InPlaceTag (&)(traits_detail::InPlaceTag);
-
-template <class T>
-using in_place_type_t =
- traits_detail::InPlaceTypeTag<T> (&)(traits_detail::InPlaceTypeTag<T>);
-
-template <std::size_t I>
-using in_place_index_t =
- traits_detail::InPlaceIndexTag<I> (&)(traits_detail::InPlaceIndexTag<I>);
-
-inline traits_detail::InPlaceTag in_place(traits_detail::InPlaceTag = {}) {
- return {};
-}
-
-template <class T>
-inline traits_detail::InPlaceTypeTag<T> in_place(
- traits_detail::InPlaceTypeTag<T> = {}) {
- return {};
-}
-
-template <std::size_t I>
-inline traits_detail::InPlaceIndexTag<I> in_place(
- traits_detail::InPlaceIndexTag<I> = {}) {
- return {};
-}
-
-// For backwards compatibility:
-using construct_in_place_t = in_place_t;
-
-inline traits_detail::InPlaceTag construct_in_place(
- traits_detail::InPlaceTag = {}) {
- return {};
-}
-
-/**
- * Initializer lists are a powerful compile time syntax introduced in C++11
- * but due to their often conflicting syntax they are not used by APIs for
- * construction.
- *
- * Further standard conforming compilers *strongly* favor an
- * std::initalizer_list overload for construction if one exists. The
- * following is a simple tag used to disambiguate construction with
- * initializer lists and regular uniform initialization.
- *
- * For example consider the following case
- *
- * class Something {
- * public:
- * explicit Something(int);
- * Something(std::intiializer_list<int>);
- *
- * operator int();
- * };
- *
- * ...
- * Something something{1}; // SURPRISE!!
- *
- * The last call to instantiate the Something object will go to the
- * initializer_list overload. Which may be surprising to users.
- *
- * If however this tag was used to disambiguate such construction it would be
- * easy for users to see which construction overload their code was referring
- * to. For example
- *
- * class Something {
- * public:
- * explicit Something(int);
- * Something(folly::initlist_construct_t, std::initializer_list<int>);
- *
- * operator int();
- * };
- *
- * ...
- * Something something_one{1}; // not the initializer_list overload
- * Something something_two{folly::initlist_construct, {1}}; // correct
- */
-struct initlist_construct_t {};
-constexpr initlist_construct_t initlist_construct{};
-
} // namespace folly
// Assume nothing when compiling with MSVC.
#ifndef _MSC_VER
-// gcc-5.0 changed string's implementation in libgcc to be non-relocatable
-#if __GNUC__ < 5
+// gcc-5.0 changed string's implementation in libstdc++ to be non-relocatable
+#if !_GLIBCXX_USE_CXX11_ABI
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_3(std::basic_string)
#endif
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::vector)
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_2(std::unique_ptr)
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(std::shared_ptr)
FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(std::function)
-
-// Boost
-FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(boost::shared_ptr)
#endif
/* Some combinations of compilers and C++ libraries make __int128 and