a0839b14df
The implementation of tuple's constructors and assignment operators currently diverges from the way the Standard specifies them, which leads to subtle cases where the behavior is not as specified. In particular, a class derived from a tuple-like type (e.g. pair) can't be assigned to a tuple with corresponding members, when it should. This commit re-implements the assignment operators (BUT NOT THE CONSTRUCTORS) in a way much closer to the specification to get rid of this bug. Most of the tests have been stolen from Eric's patch https://reviews.llvm.org/D27606. As a fly-by improvement, tests for noexcept correctness have been added to all overloads of operator=. We should tackle the same issue for the tuple constructors in a future patch - I'm just trying to make progress on fixing this long-standing bug. PR17550 rdar://15837420 Differential Revision: https://reviews.llvm.org/D50106
73 lines
2.5 KiB
C++
73 lines
2.5 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// <tuple>
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// template <class... Types> class tuple;
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// template <class U1, class U2>
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// tuple& operator=(const pair<U1, U2>& u);
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// UNSUPPORTED: c++03
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#include <cassert>
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#include <memory>
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#include <tuple>
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#include <type_traits>
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#include <utility>
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struct NothrowCopyAssignable {
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NothrowCopyAssignable& operator=(NothrowCopyAssignable const&) noexcept { return *this; }
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};
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struct PotentiallyThrowingCopyAssignable {
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PotentiallyThrowingCopyAssignable& operator=(PotentiallyThrowingCopyAssignable const&) { return *this; }
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};
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#include "test_macros.h"
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int main(int, char**)
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{
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{
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typedef std::pair<long, char> T0;
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typedef std::tuple<long long, short> T1;
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T0 t0(2, 'a');
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T1 t1;
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t1 = t0;
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assert(std::get<0>(t1) == 2);
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assert(std::get<1>(t1) == short('a'));
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}
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{
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// test that the implicitly generated copy assignment operator
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// is properly deleted
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using T = std::tuple<int, int>;
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using P = std::tuple<std::unique_ptr<int>, std::unique_ptr<int>>;
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static_assert(!std::is_assignable<T, const P &>::value, "");
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}
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{
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typedef std::tuple<NothrowCopyAssignable, long> Tuple;
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typedef std::pair<NothrowCopyAssignable, int> Pair;
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static_assert(std::is_nothrow_assignable<Tuple&, Pair const&>::value, "");
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static_assert(std::is_nothrow_assignable<Tuple&, Pair&>::value, "");
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static_assert(std::is_nothrow_assignable<Tuple&, Pair const&&>::value, "");
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}
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{
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typedef std::tuple<PotentiallyThrowingCopyAssignable, long> Tuple;
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typedef std::pair<PotentiallyThrowingCopyAssignable, int> Pair;
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static_assert(std::is_assignable<Tuple&, Pair const&>::value, "");
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static_assert(!std::is_nothrow_assignable<Tuple&, Pair const&>::value, "");
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static_assert(std::is_assignable<Tuple&, Pair&>::value, "");
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static_assert(!std::is_nothrow_assignable<Tuple&, Pair&>::value, "");
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static_assert(std::is_assignable<Tuple&, Pair const&&>::value, "");
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static_assert(!std::is_nothrow_assignable<Tuple&, Pair const&&>::value, "");
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}
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return 0;
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}
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