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libstdc++: Optimize std::destructible concept

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This uses variable templates and constraints to define a much simpler
std::destructible concept. This avoids instantiating the trait
std::is_nothrow_destructible and all its implementation in terms of
__is_destructible_safe and __is_destructible_impl.

If we had an intrinsic we could just use that (PR c++/107600).

libstdc++-v3/ChangeLog:

	* include/std/concepts (__detail::__destructible_impl)
	(__detail::__destructible): New variable templates.
	(destructible): Use __detail::__destructible.
	* testsuite/std/concepts/concepts.lang/concept.destructible/1.cc:
	Add more checks for array and reference types.
This commit is contained in:
Jonathan Wakely 2022-11-10 01:30:45 +00:00
parent 1cdfd0e5cd
commit 0cbb756fe9
2 changed files with 25 additions and 4 deletions
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24
libstdc++-v3/include/std/concepts
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@ -113,9 +113,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
using __cref = const remove_reference_t<_Tp>&;
template<typename _Tp>
concept __class_or_enum
= is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
template<typename _Tp>
concept __class_or_enum
= is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
template<typename _Tp>
constexpr bool __destructible_impl = false;
template<typename _Tp>
requires requires(_Tp& __t) { { __t.~_Tp() } noexcept; }
constexpr bool __destructible_impl<_Tp> = true;
template<typename _Tp>
constexpr bool __destructible = __destructible_impl<_Tp>;
template<typename _Tp>
constexpr bool __destructible<_Tp&> = true;
template<typename _Tp>
constexpr bool __destructible<_Tp&&> = true;
template<typename _Tp, size_t _Nm>
constexpr bool __destructible<_Tp[_Nm]> = __destructible<_Tp>;
} // namespace __detail
/// [concept.assignable], concept assignable_from
@ -129,7 +145,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// [concept.destructible], concept destructible
template<typename _Tp>
concept destructible = is_nothrow_destructible_v<_Tp>;
concept destructible = __detail::__destructible<_Tp>;
/// [concept.constructible], concept constructible_from
template<typename _Tp, typename... _Args>

5
libstdc++-v3/testsuite/std/concepts/concepts.lang/concept.destructible/1.cc
View File

@ -29,6 +29,7 @@ static_assert( std::destructible<int&&> );
static_assert( std::destructible<const int&> );
static_assert( !std::destructible<int[]> );
static_assert( std::destructible<int[2]> );
static_assert( std::destructible<int[2][3]> );
static_assert( !std::destructible<int()> );
static_assert( std::destructible<int(*)()> );
static_assert( std::destructible<int(&)()> );
@ -47,6 +48,8 @@ struct C
~C() noexcept(false) { }
};
static_assert( !std::destructible<C> );
static_assert( std::destructible<C&> );
static_assert( !std::destructible<C[1]> );
class D
{
public:
@ -55,3 +58,5 @@ private:
~D() { }
};
static_assert( !std::destructible<D> );
static_assert( std::destructible<D&> );
static_assert( !std::destructible<D[1]> );