- 2f6a3c92ce0f64e0923ad326ec5d07eae03061fd Add C++14's std::exchange to absl/utility/utility.h. by Abseil Team <absl-team@google.com>

- 9f2c9adbf998dd9062c8cc3da1076bde87081d71 Fix comment typo. by Greg Falcon <gfalcon@google.com>

GitOrigin-RevId: 2f6a3c92ce0f64e0923ad326ec5d07eae03061fd
Change-Id: I7b9db94ad315092baefe56b02f250acadafbe312
This commit is contained in:
Abseil Team 2018-04-25 10:38:08 -07:00 committed by Derek Mauro
parent 19b3c95727
commit ea0e750e52
3 changed files with 31 additions and 1 deletions

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@ -40,7 +40,7 @@ void InitializeSymbolizer(const char *argv0) {
SymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_UNDNAME); SymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_UNDNAME);
if (!SymInitialize(process, nullptr, true)) { if (!SymInitialize(process, nullptr, true)) {
// GetLastError() returns a Win32 DWORD, but we assign to // GetLastError() returns a Win32 DWORD, but we assign to
// unsigned long to simplify the ABSL_RAW_LOG case below. The uniform // unsigned long long to simplify the ABSL_RAW_LOG case below. The uniform
// initialization guarantees this is not a narrowing conversion. // initialization guarantees this is not a narrowing conversion.
const unsigned long long error{GetLastError()}; // NOLINT(runtime/int) const unsigned long long error{GetLastError()}; // NOLINT(runtime/int)
ABSL_RAW_LOG(FATAL, "SymInitialize() failed: %llu", error); ABSL_RAW_LOG(FATAL, "SymInitialize() failed: %llu", error);

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@ -24,6 +24,7 @@
// * make_index_sequence<N> == std::make_index_sequence<N> // * make_index_sequence<N> == std::make_index_sequence<N>
// * index_sequence_for<Ts...> == std::index_sequence_for<Ts...> // * index_sequence_for<Ts...> == std::index_sequence_for<Ts...>
// * apply<Functor, Tuple> == std::apply<Functor, Tuple> // * apply<Functor, Tuple> == std::apply<Functor, Tuple>
// * exchange<T> == std::exchange<T>
// //
// This header file also provides the tag types `in_place_t`, `in_place_type_t`, // This header file also provides the tag types `in_place_t`, `in_place_type_t`,
// and `in_place_index_t`, as well as the constant `in_place`, and // and `in_place_index_t`, as well as the constant `in_place`, and
@ -264,6 +265,27 @@ auto apply(Functor&& functor, Tuple&& t)
absl::make_index_sequence<std::tuple_size< absl::make_index_sequence<std::tuple_size<
typename std::remove_reference<Tuple>::type>::value>{}); typename std::remove_reference<Tuple>::type>::value>{});
} }
// exchange
//
// Replaces the value of `obj` with `new_value` and returns the old value of
// `obj`. `absl::exchange` is designed to be a drop-in replacement for C++14's
// `std::exchange`.
//
// Example:
//
// Foo& operator=(Foo&& other) {
// ptr1_ = absl::exchange(other.ptr1_, nullptr);
// int1_ = absl::exchange(other.int1_, -1);
// return *this;
// }
template <typename T, typename U = T>
T exchange(T& obj, U&& new_value) {
T old_value = absl::move(obj);
obj = absl::forward<U>(new_value);
return old_value;
}
} // namespace absl } // namespace absl
#endif // ABSL_UTILITY_UTILITY_H_ #endif // ABSL_UTILITY_UTILITY_H_

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@ -333,5 +333,13 @@ TEST(ApplyTest, FlipFlop) {
EXPECT_EQ(42, absl::apply(&FlipFlop::member, std::make_tuple(obj))); EXPECT_EQ(42, absl::apply(&FlipFlop::member, std::make_tuple(obj)));
} }
TEST(ExchangeTest, MoveOnly) {
auto a = Factory(1);
EXPECT_EQ(1, *a);
auto b = absl::exchange(a, Factory(2));
EXPECT_EQ(2, *a);
EXPECT_EQ(1, *b);
}
} // namespace } // namespace