TraitsTest.cpp

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/*
 * Copyright 2012-present 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.
 */

#include <folly/Traits.h>

#include <cstring>
#include <string>
#include <type_traits>
#include <utility>

#include <folly/ScopeGuard.h>
#include <folly/portability/GTest.h>

using namespace folly;
using namespace std;

namespace {

FOLLY_CREATE_HAS_MEMBER_TYPE_TRAITS(has_member_type_x, x);
} // namespace

TEST(Traits, has_member_type) {
  struct membership_no {};
  struct membership_yes {
    using x = void;
  };

  EXPECT_TRUE((is_same<false_type, has_member_type_x<membership_no>>::value));
  EXPECT_TRUE((is_same<true_type, has_member_type_x<membership_yes>>::value));
}

//  Note: FOLLY_CREATE_HAS_MEMBER_FN_TRAITS tests are in
//  folly/test/HasMemberFnTraitsTest.cpp.

struct T1 {}; // old-style IsRelocatable, below
struct T2 {}; // old-style IsRelocatable, below
struct T3 {
  typedef std::true_type IsRelocatable;
};
struct T5 : T3 {};

struct F1 {};
struct F2 {
  typedef int IsRelocatable;
};
struct F3 : T3 {
  typedef std::false_type IsRelocatable;
};
struct F4 : T1 {};

namespace folly {
template <>
struct IsRelocatable<T1> : std::true_type {};
template <>
FOLLY_ASSUME_RELOCATABLE(T2);
} // namespace folly

TEST(Traits, scalars) {
  EXPECT_TRUE(IsRelocatable<int>::value);
  EXPECT_TRUE(IsRelocatable<bool>::value);
  EXPECT_TRUE(IsRelocatable<double>::value);
  EXPECT_TRUE(IsRelocatable<void*>::value);
}

TEST(Traits, containers) {
  EXPECT_TRUE(IsRelocatable<vector<F1>>::value);
  EXPECT_TRUE((IsRelocatable<pair<F1, F1>>::value));
  EXPECT_TRUE((IsRelocatable<pair<T1, T2>>::value));
}

TEST(Traits, original) {
  EXPECT_TRUE(IsRelocatable<T1>::value);
  EXPECT_TRUE(IsRelocatable<T2>::value);
}

TEST(Traits, typedefd) {
  EXPECT_TRUE(IsRelocatable<T3>::value);
  EXPECT_TRUE(IsRelocatable<T5>::value);
  EXPECT_FALSE(IsRelocatable<F2>::value);
  EXPECT_FALSE(IsRelocatable<F3>::value);
}

TEST(Traits, unset) {
  EXPECT_TRUE(IsRelocatable<F1>::value);
  EXPECT_TRUE(IsRelocatable<F4>::value);
}

TEST(Traits, bitAndInit) {
  EXPECT_TRUE(IsZeroInitializable<int>::value);
  EXPECT_FALSE(IsZeroInitializable<vector<int>>::value);
}

TEST(Trait, logicOperators) {
  static_assert(Conjunction<true_type>::value, "");
  static_assert(!Conjunction<false_type>::value, "");
  static_assert(is_same<Conjunction<true_type>::type, true_type>::value, "");
  static_assert(is_same<Conjunction<false_type>::type, false_type>::value, "");
  static_assert(Conjunction<true_type, true_type>::value, "");
  static_assert(!Conjunction<true_type, false_type>::value, "");

  static_assert(Disjunction<true_type>::value, "");
  static_assert(!Disjunction<false_type>::value, "");
  static_assert(is_same<Disjunction<true_type>::type, true_type>::value, "");
  static_assert(is_same<Disjunction<false_type>::type, false_type>::value, "");
  static_assert(Disjunction<true_type, true_type>::value, "");
  static_assert(Disjunction<true_type, false_type>::value, "");

  static_assert(!Negation<true_type>::value, "");
  static_assert(Negation<false_type>::value, "");
}

TEST(Traits, is_negative) {
  EXPECT_TRUE(folly::is_negative(-1));
  EXPECT_FALSE(folly::is_negative(0));
  EXPECT_FALSE(folly::is_negative(1));
  EXPECT_FALSE(folly::is_negative(0u));
  EXPECT_FALSE(folly::is_negative(1u));

  EXPECT_TRUE(folly::is_non_positive(-1));
  EXPECT_TRUE(folly::is_non_positive(0));
  EXPECT_FALSE(folly::is_non_positive(1));
  EXPECT_TRUE(folly::is_non_positive(0u));
  EXPECT_FALSE(folly::is_non_positive(1u));
}

TEST(Traits, relational) {
  // We test, especially, the edge cases to make sure we don't
  // trip -Wtautological-comparisons

  EXPECT_FALSE((folly::less_than<uint8_t, 0u, uint8_t>(0u)));
  EXPECT_FALSE((folly::less_than<uint8_t, 0u, uint8_t>(254u)));
  EXPECT_FALSE((folly::less_than<uint8_t, 255u, uint8_t>(255u)));
  EXPECT_TRUE((folly::less_than<uint8_t, 255u, uint8_t>(254u)));

  EXPECT_FALSE((folly::greater_than<uint8_t, 0u, uint8_t>(0u)));
  EXPECT_TRUE((folly::greater_than<uint8_t, 0u, uint8_t>(254u)));
  EXPECT_FALSE((folly::greater_than<uint8_t, 255u, uint8_t>(255u)));
  EXPECT_FALSE((folly::greater_than<uint8_t, 255u, uint8_t>(254u)));
}

#if FOLLY_HAVE_INT128_T

TEST(Traits, int128) {
  EXPECT_TRUE(
      (::std::is_same<::std::make_unsigned<__int128_t>::type, __uint128_t>::
           value));
  EXPECT_TRUE((
      ::std::is_same<::std::make_signed<__int128_t>::type, __int128_t>::value));
  EXPECT_TRUE(
      (::std::is_same<::std::make_unsigned<__uint128_t>::type, __uint128_t>::
           value));
  EXPECT_TRUE(
      (::std::is_same<::std::make_signed<__uint128_t>::type, __int128_t>::
           value));
  EXPECT_TRUE((::std::is_arithmetic<__int128_t>::value));
  EXPECT_TRUE((::std::is_arithmetic<__uint128_t>::value));
  EXPECT_TRUE((::std::is_integral<__int128_t>::value));
  EXPECT_TRUE((::std::is_integral<__uint128_t>::value));
  EXPECT_FALSE((::std::is_unsigned<__int128_t>::value));
  EXPECT_TRUE((::std::is_signed<__int128_t>::value));
  EXPECT_TRUE((::std::is_unsigned<__uint128_t>::value));
  EXPECT_FALSE((::std::is_signed<__uint128_t>::value));
  EXPECT_TRUE((::std::is_fundamental<__int128_t>::value));
  EXPECT_TRUE((::std::is_fundamental<__uint128_t>::value));
  EXPECT_TRUE((::std::is_scalar<__int128_t>::value));
  EXPECT_TRUE((::std::is_scalar<__uint128_t>::value));
}

#endif // FOLLY_HAVE_INT128_T

template <typename T, typename... Args>
void testIsRelocatable(Args&&... args) {
  if (!IsRelocatable<T>::value) {
    return;
  }

  // We use placement new on zeroed memory to avoid garbage subsections
  char vsrc[sizeof(T)] = {0};
  char vdst[sizeof(T)] = {0};
  char vcpy[sizeof(T)];

  T* src = new (vsrc) T(std::forward<Args>(args)...);
  SCOPE_EXIT {
    src->~T();
  };
  std::memcpy(vcpy, vsrc, sizeof(T));
  T deep(*src);
  T* dst = new (vdst) T(std::move(*src));
  SCOPE_EXIT {
    dst->~T();
  };

  EXPECT_EQ(deep, *dst);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstrict-aliasing"
  EXPECT_EQ(deep, *reinterpret_cast<T*>(vcpy));
#pragma GCC diagnostic pop

  // This test could technically fail; however, this is what relocation
  // almost always means, so it's a good test to have
  EXPECT_EQ(std::memcmp(vcpy, vdst, sizeof(T)), 0);
}

TEST(Traits, actuallyRelocatable) {
  // Ensure that we test stack and heap allocation for strings with in-situ
  // capacity
  testIsRelocatable<std::string>("1");
  testIsRelocatable<std::string>(sizeof(std::string) + 1, 'x');

  testIsRelocatable<std::vector<char>>(5, 'g');
}

namespace {
// 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 {};

struct some_tag {};

template <typename T>
struct container {
  template <class... Args>
  container(
      folly::type_t<some_tag, decltype(T(std::declval<Args>()...))>,
      Args&&...) {}
};
} // namespace

TEST(Traits, void_t) {
  EXPECT_TRUE((::std::is_same<folly::void_t<>, void>::value));
  EXPECT_TRUE((::std::is_same<folly::void_t<int>, void>::value));
  EXPECT_TRUE((::std::is_same<folly::void_t<int, short>, void>::value));
  EXPECT_TRUE(
      (::std::is_same<folly::void_t<int, short, std::string>, void>::value));
  EXPECT_TRUE((::has_value_type<std::string>::value));
  EXPECT_FALSE((::has_value_type<int>::value));
}

TEST(Traits, type_t) {
  EXPECT_TRUE((::std::is_same<folly::type_t<float>, float>::value));
  EXPECT_TRUE((::std::is_same<folly::type_t<float, int>, float>::value));
  EXPECT_TRUE((::std::is_same<folly::type_t<float, int, short>, float>::value));
  EXPECT_TRUE(
      (::std::is_same<folly::type_t<float, int, short, std::string>, float>::
           value));
  EXPECT_TRUE((
      ::std::is_constructible<::container<std::string>, some_tag, std::string>::
          value));
  EXPECT_FALSE(
      (::std::is_constructible<::container<std::string>, some_tag, float>::
           value));
}

TEST(Traits, remove_cvref) {
  using folly::remove_cvref;
  using folly::remove_cvref_t;

  // test all possible c-ref qualifiers without volatile
  EXPECT_TRUE((std::is_same<remove_cvref_t<int>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int&&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int&&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int const>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int const>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int const&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int const&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int const&&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int const&&>::type, int>::value));

  // test all possible c-ref qualifiers with volatile
  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int volatile>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile&&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int volatile&&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile&>, int>::value));
  EXPECT_TRUE((std::is_same<remove_cvref<int volatile&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile const>, int>::value));
  EXPECT_TRUE(
      (std::is_same<remove_cvref<int volatile const>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile const&>, int>::value));
  EXPECT_TRUE(
      (std::is_same<remove_cvref<int volatile const&>::type, int>::value));

  EXPECT_TRUE((std::is_same<remove_cvref_t<int volatile const&&>, int>::value));
  EXPECT_TRUE(
      (std::is_same<remove_cvref<int volatile const&&>::type, int>::value));
}

TEST(Traits, like) {
  EXPECT_TRUE((std::is_same<like_t<int, char>, char>::value));
  EXPECT_TRUE((std::is_same<like_t<int const, char>, char const>::value));
  EXPECT_TRUE((std::is_same<like_t<int volatile, char>, char volatile>::value));
  EXPECT_TRUE(
      (std::is_same<like_t<int const volatile, char>, char const volatile>::
           value));
  EXPECT_TRUE((std::is_same<like_t<int&, char>, char&>::value));
  EXPECT_TRUE((std::is_same<like_t<int const&, char>, char const&>::value));
  EXPECT_TRUE(
      (std::is_same<like_t<int volatile&, char>, char volatile&>::value));
  EXPECT_TRUE(
      (std::is_same<like_t<int const volatile&, char>, char const volatile&>::
           value));
  EXPECT_TRUE((std::is_same<like_t<int&&, char>, char&&>::value));
  EXPECT_TRUE((std::is_same<like_t<int const&&, char>, char const&&>::value));
  EXPECT_TRUE(
      (std::is_same<like_t<int volatile&&, char>, char volatile&&>::value));
  EXPECT_TRUE(
      (std::is_same<like_t<int const volatile&&, char>, char const volatile&&>::
           value));
}