Louis Dionne 02540b2f6d
[libc++] Make sure ranges algorithms and views handle boolean-testable correctly (#69378)
Before this patch, we would fail to implicitly convert the result of
predicates to bool, which means we'd potentially perform a copy or move
construction of the boolean-testable, which isn't allowed. The same
holds true for comparing iterators against sentinels, which is allowed
to return a boolean-testable type.

We already had tests aiming to ensure correct handling of these types,
but they failed to provide appropriate coverage in several cases due to
guaranteed RVO. This patch fixes the tests, adds tests for missing
algorithms and views, and fixes the actual problems in the code.

Fixes #69074
2023-11-06 21:19:49 -10:00

103 lines
3.8 KiB
C++

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ALGORITHM_RANGES_MAX_H
#define _LIBCPP___ALGORITHM_RANGES_MAX_H
#include <__algorithm/ranges_min_element.h>
#include <__assert>
#include <__concepts/copyable.h>
#include <__config>
#include <__functional/identity.h>
#include <__functional/invoke.h>
#include <__functional/ranges_operations.h>
#include <__iterator/concepts.h>
#include <__iterator/projected.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__type_traits/is_trivially_copyable.h>
#include <__utility/move.h>
#include <initializer_list>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
#if _LIBCPP_STD_VER >= 20
_LIBCPP_PUSH_MACROS
# include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
namespace ranges {
namespace __max {
struct __fn {
template <class _Tp,
class _Proj = identity,
indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr const _Tp&
operator()(_LIBCPP_LIFETIMEBOUND const _Tp& __a,
_LIBCPP_LIFETIMEBOUND const _Tp& __b,
_Comp __comp = {},
_Proj __proj = {}) const {
return std::invoke(__comp, std::invoke(__proj, __a), std::invoke(__proj, __b)) ? __b : __a;
}
template <copyable _Tp,
class _Proj = identity,
indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Tp
operator()(initializer_list<_Tp> __il, _Comp __comp = {}, _Proj __proj = {}) const {
_LIBCPP_ASSERT_UNCATEGORIZED(__il.begin() != __il.end(), "initializer_list must contain at least one element");
auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) -> bool { return std::invoke(__comp, __rhs, __lhs); };
return *ranges::__min_element_impl(__il.begin(), __il.end(), __comp_lhs_rhs_swapped, __proj);
}
template <input_range _Rp,
class _Proj = identity,
indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
requires indirectly_copyable_storable<iterator_t<_Rp>, range_value_t<_Rp>*>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr range_value_t<_Rp>
operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
auto __first = ranges::begin(__r);
auto __last = ranges::end(__r);
_LIBCPP_ASSERT_UNCATEGORIZED(__first != __last, "range must contain at least one element");
if constexpr (forward_range<_Rp> && !__is_cheap_to_copy<range_value_t<_Rp>>) {
auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) -> bool {
return std::invoke(__comp, __rhs, __lhs);
};
return *ranges::__min_element_impl(std::move(__first), std::move(__last), __comp_lhs_rhs_swapped, __proj);
} else {
range_value_t<_Rp> __result = *__first;
while (++__first != __last) {
if (std::invoke(__comp, std::invoke(__proj, __result), std::invoke(__proj, *__first)))
__result = *__first;
}
return __result;
}
}
};
} // namespace __max
inline namespace __cpo {
inline constexpr auto max = __max::__fn{};
} // namespace __cpo
} // namespace ranges
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP_STD_VER >= 20 &&
#endif // _LIBCPP___ALGORITHM_RANGES_MAX_H