- 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
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3 changed files with 31 additions and 1 deletions
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@ -40,7 +40,7 @@ void InitializeSymbolizer(const char *argv0) {
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SymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_UNDNAME);
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if (!SymInitialize(process, nullptr, true)) {
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// GetLastError() returns a Win32 DWORD, but we assign to
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// unsigned long to simplify the ABSL_RAW_LOG case below. The uniform
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// unsigned long long to simplify the ABSL_RAW_LOG case below. The uniform
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// initialization guarantees this is not a narrowing conversion.
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const unsigned long long error{GetLastError()}; // NOLINT(runtime/int)
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ABSL_RAW_LOG(FATAL, "SymInitialize() failed: %llu", error);
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@ -24,6 +24,7 @@
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// * make_index_sequence<N> == std::make_index_sequence<N>
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// * index_sequence_for<Ts...> == std::index_sequence_for<Ts...>
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// * apply<Functor, Tuple> == std::apply<Functor, Tuple>
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// * exchange<T> == std::exchange<T>
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//
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// This header file also provides the tag types `in_place_t`, `in_place_type_t`,
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// and `in_place_index_t`, as well as the constant `in_place`, and
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@ -264,6 +265,27 @@ auto apply(Functor&& functor, Tuple&& t)
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absl::make_index_sequence<std::tuple_size<
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typename std::remove_reference<Tuple>::type>::value>{});
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}
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// exchange
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//
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// Replaces the value of `obj` with `new_value` and returns the old value of
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// `obj`. `absl::exchange` is designed to be a drop-in replacement for C++14's
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// `std::exchange`.
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//
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// Example:
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//
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// Foo& operator=(Foo&& other) {
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// ptr1_ = absl::exchange(other.ptr1_, nullptr);
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// int1_ = absl::exchange(other.int1_, -1);
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// return *this;
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// }
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template <typename T, typename U = T>
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T exchange(T& obj, U&& new_value) {
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T old_value = absl::move(obj);
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obj = absl::forward<U>(new_value);
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return old_value;
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}
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} // namespace absl
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#endif // ABSL_UTILITY_UTILITY_H_
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@ -333,5 +333,13 @@ TEST(ApplyTest, FlipFlop) {
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EXPECT_EQ(42, absl::apply(&FlipFlop::member, std::make_tuple(obj)));
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}
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TEST(ExchangeTest, MoveOnly) {
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auto a = Factory(1);
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EXPECT_EQ(1, *a);
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auto b = absl::exchange(a, Factory(2));
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EXPECT_EQ(2, *a);
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EXPECT_EQ(1, *b);
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}
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} // namespace
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