7265ff928a
The Standard is currently unimplementable. We have to pick between:
1. Not implementing constexpr support properly in std::array<T, 0>
2. Making std::array<T, 0> non-trivial even when T is trivial
3. Returning nullptr from std::array<T, 0>::begin()
Libc++ initially picked (1). In 77b9abfc8e, we started implementing constexpr properly, but lost the guarantee of triviality. Since it seems like both (1) and (2) are really important, it seems like (3) is the only viable option for libc++, after all. This is also what other implementations are doing.
This patch moves libc++ from (1) to (3).
It also:
- Improves the test coverage for the various ways of initializing std::array
- Adds tests for the triviality of std::array
- Adds tests for the aggregate-ness of std::array
Reviewed By: #libc, miscco, EricWF, zoecarver
Differential Revision: https://reviews.llvm.org/D80821
100 lines
2.2 KiB
C++
100 lines
2.2 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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// <array>
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// T *data();
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#include <array>
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#include <cassert>
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#include <cstddef> // for std::max_align_t
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#include "test_macros.h"
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// std::array is explicitly allowed to be initialized with A a = { init-list };.
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// Disable the missing braces warning for this reason.
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#include "disable_missing_braces_warning.h"
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struct NoDefault {
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TEST_CONSTEXPR NoDefault(int) { }
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};
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#if TEST_STD_VER < 11
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struct natural_alignment {
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long t1;
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long long t2;
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double t3;
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long double t4;
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};
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#endif
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TEST_CONSTEXPR_CXX17 bool tests()
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{
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{
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typedef double T;
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typedef std::array<T, 3> C;
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C c = {1, 2, 3.5};
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T* p = c.data();
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assert(p[0] == 1);
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assert(p[1] == 2);
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assert(p[2] == 3.5);
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}
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{
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typedef double T;
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typedef std::array<T, 0> C;
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C c = {};
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T* p = c.data();
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(void)p;
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}
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{
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typedef double T;
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typedef std::array<const T, 0> C;
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C c = {{}};
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const T* p = c.data();
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(void)p;
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static_assert((std::is_same<decltype(c.data()), const T*>::value), "");
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}
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{
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typedef NoDefault T;
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typedef std::array<T, 0> C;
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C c = {};
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T* p = c.data();
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(void)p;
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}
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{
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std::array<int, 5> c = {0, 1, 2, 3, 4};
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assert(c.data() == &c[0]);
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assert(*c.data() == c[0]);
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}
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return true;
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}
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int main(int, char**)
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{
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tests();
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#if TEST_STD_VER >= 17
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static_assert(tests(), "");
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#endif
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// Test the alignment of data()
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{
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#if TEST_STD_VER < 11
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typedef natural_alignment T;
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#else
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typedef std::max_align_t T;
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#endif
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typedef std::array<T, 0> C;
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const C c = {};
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const T* p = c.data();
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std::uintptr_t pint = reinterpret_cast<std::uintptr_t>(p);
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assert(pint % TEST_ALIGNOF(T) == 0);
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}
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return 0;
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}
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