Export of internal Abseil changes.

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ac7508120c60dfe689c40929e416b6a486f83ee3 by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 206912089

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bd709faba88565367b6d337466e6456481b5f3e8 by Matt Calabrese <calabrese@google.com>:

Implement `std::experimental::is_detected` in type_traits internals and move `is_detected_convertible` from variant's internals to type_traits internals. This is in preparation of creating workarounds for broken standard traits.

PiperOrigin-RevId: 206825598

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0dbddea569370eb9b6348cee172d1874f9046eb4 by Jorg Brown <jorg@google.com>:

Support users who turn on floating-point conversion warnings

PiperOrigin-RevId: 206813209

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30991f757c8f0100584619d8a9c41897d029f112 by Jorg Brown <jorg@google.com>:

Speed up the absl::Seconds() function for floating-point values, roughly by 4.5x, since
we can take advantage of the fact that we're just taking a floating-point number and
splitting it into its integral and fractional parts.

PiperOrigin-RevId: 206806270

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6883837176838aa5a517e7a8cb4c99afd24c0d12 by Jon Cohen <cohenjon@google.com>:

Remove the DISABLE_INSTALL from absl_container.  It doesn't do anything.

PiperOrigin-RevId: 206802544

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92ab14fed06e6dd1f01a0284bd7f95d3e2c0c3d8 by Jon Cohen <cohenjon@google.com>:

Internal change

PiperOrigin-RevId: 206776244

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17b76c7f364ac562d9e0faeca0320f63aa3fdb85 by Jorg Brown <jorg@google.com>:

Fix absl/strings:numbers_test flakiness due to exceeding the 1-minute timeout

PiperOrigin-RevId: 206763175

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6637843f2e198b8efd90e5577fbc86bdea43b2cc by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206354178

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bced22f81add828c9b4c60eb45554d36c22e2f96 by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206347377

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75be14a71d2d5e335812d5b7670120271fb5bd79 by Abseil Team <absl-team@google.com>:

Internal change.

PiperOrigin-RevId: 206326935

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6929e43f4c7898b1f51e441911a19092a06fbf97 by Abseil Team <absl-team@google.com>:

Adds templated allocator to absl::FixedArray with corresponding tests

PiperOrigin-RevId: 206326368

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55ae34b75ff029eb267f9519e577bab8a575b487 by Abseil Team <absl-team@google.com>:

Internal change.

PiperOrigin-RevId: 206233448

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6950a8ccddf35d451eec2d02cd28a797c8b7cf6a by Matt Kulukundis <kfm@google.com>:

Internal change

PiperOrigin-RevId: 206035613
GitOrigin-RevId: ac7508120c60dfe689c40929e416b6a486f83ee3
Change-Id: I675605abbedab6b3ac9aa82195cbd059ff7c82b1

1 files changed, 175 insertions, 0 deletions

diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h
new file mode 100644
index 000000000000..cc52614f5b37
--- /dev/null
+++ b/absl/container/internal/compressed_tuple.h
@@ -0,0 +1,175 @@
+// Copyright 2018 The Abseil Authors.
+//
+// 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.
+//
+// Helper class to perform the Empty Base Optimization.
+// Ts can contain classes and non-classes, empty or not. For the ones that
+// are empty classes, we perform the optimization. If all types in Ts are empty
+// classes, then CompressedTuple<Ts...> is itself an empty class.
+//
+// To access the members, use member get<N>() function.
+//
+// Eg:
+//   absl::container_internal::CompressedTuple<int, T1, T2, T3> value(7, t1, t2,
+//                                                                    t3);
+//   assert(value.get<0>() == 7);
+//   T1& t1 = value.get<1>();
+//   const T2& t2 = value.get<2>();
+//   ...
+//
+// http://en.cppreference.com/w/cpp/language/ebo
+
+#ifndef ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_
+#define ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "absl/utility/utility.h"
+
+#ifdef _MSC_VER
+// We need to mark these classes with this declspec to ensure that
+// CompressedTuple happens.
+#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC __declspec(empty_bases)
+#else  // _MSC_VER
+#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
+#endif  // _MSC_VER
+
+namespace absl {
+namespace container_internal {
+
+template <typename... Ts>
+class CompressedTuple;
+
+namespace internal_compressed_tuple {
+
+template <typename D, size_t I>
+struct Elem;
+template <typename... B, size_t I>
+struct Elem<CompressedTuple<B...>, I>
+    : std::tuple_element<I, std::tuple<B...>> {};
+template <typename D, size_t I>
+using ElemT = typename Elem<D, I>::type;
+
+// Use the __is_final intrinsic if available. Where it's not available, classes
+// declared with the 'final' specifier cannot be used as CompressedTuple
+// elements.
+// TODO(sbenza): Replace this with std::is_final in C++14.
+template <typename T>
+constexpr bool IsFinal() {
+#if defined(__clang__) || defined(__GNUC__)
+  return __is_final(T);
+#else
+  return false;
+#endif
+}
+
+template <typename T>
+constexpr bool ShouldUseBase() {
+  return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>();
+}
+
+// The storage class provides two specializations:
+//  - For empty classes, it stores T as a base class.
+//  - For everything else, it stores T as a member.
+template <typename D, size_t I, bool = ShouldUseBase<ElemT<D, I>>()>
+struct Storage {
+  using T = ElemT<D, I>;
+  T value;
+  constexpr Storage() = default;
+  explicit constexpr Storage(T&& v) : value(absl::forward<T>(v)) {}
+  constexpr const T& get() const { return value; }
+  T& get() { return value; }
+};
+
+template <typename D, size_t I>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<D, I, true>
+    : ElemT<D, I> {
+  using T = internal_compressed_tuple::ElemT<D, I>;
+  constexpr Storage() = default;
+  explicit constexpr Storage(T&& v) : T(absl::forward<T>(v)) {}
+  constexpr const T& get() const { return *this; }
+  T& get() { return *this; }
+};
+
+template <typename D, typename I>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl;
+
+template <typename... Ts, size_t... I>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
+    CompressedTupleImpl<CompressedTuple<Ts...>, absl::index_sequence<I...>>
+    // We use the dummy identity function through std::integral_constant to
+    // convince MSVC of accepting and expanding I in that context. Without it
+    // you would get:
+    //   error C3548: 'I': parameter pack cannot be used in this context
+    : Storage<CompressedTuple<Ts...>,
+              std::integral_constant<size_t, I>::value>... {
+  constexpr CompressedTupleImpl() = default;
+  explicit constexpr CompressedTupleImpl(Ts&&... args)
+      : Storage<CompressedTuple<Ts...>, I>(absl::forward<Ts>(args))... {}
+};
+
+}  // namespace internal_compressed_tuple
+
+// Helper class to perform the Empty Base Class Optimization.
+// Ts can contain classes and non-classes, empty or not. For the ones that
+// are empty classes, we perform the CompressedTuple. If all types in Ts are
+// empty classes, then CompressedTuple<Ts...> is itself an empty class.
+//
+// To access the members, use member .get<N>() function.
+//
+// Eg:
+//   absl::container_internal::CompressedTuple<int, T1, T2, T3> value(7, t1, t2,
+//                                                                    t3);
+//   assert(value.get<0>() == 7);
+//   T1& t1 = value.get<1>();
+//   const T2& t2 = value.get<2>();
+//   ...
+//
+// http://en.cppreference.com/w/cpp/language/ebo
+template <typename... Ts>
+class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple
+    : private internal_compressed_tuple::CompressedTupleImpl<
+          CompressedTuple<Ts...>, absl::index_sequence_for<Ts...>> {
+ private:
+  template <int I>
+  using ElemT = internal_compressed_tuple::ElemT<CompressedTuple, I>;
+
+ public:
+  constexpr CompressedTuple() = default;
+  explicit constexpr CompressedTuple(Ts... base)
+      : CompressedTuple::CompressedTupleImpl(absl::forward<Ts>(base)...) {}
+
+  template <int I>
+  ElemT<I>& get() {
+    return internal_compressed_tuple::Storage<CompressedTuple, I>::get();
+  }
+
+  template <int I>
+  constexpr const ElemT<I>& get() const {
+    return internal_compressed_tuple::Storage<CompressedTuple, I>::get();
+  }
+};
+
+// Explicit specialization for a zero-element tuple
+// (needed to avoid ambiguous overloads for the default constructor).
+template <>
+class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple<> {};
+
+}  // namespace container_internal
+}  // namespace absl
+
+#undef ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
+
+#endif  // ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_