libstdc++: Fix std::allocator<void> for versioned namespace
Removing the allocator<void> specialization for the versioned namespace breaks _Extptr_allocator<void> because the allocator<void> specialization was still declared in <bits/memoryfwd.h>, making it an incomplete type. It wrong to remove that specialization anyway, because it is still needed pre-C++20. This removes the #if ! _GLIBCXX_INLINE_VERSION check, so that allocator<void> is still explicitly specialized for the versioned namespace, consistent with the normal unversioned namespace mode. To make _Extptr_allocator<void> usable as a ProtoAllocator, this change adds a default constructor and converting constructor. That is consistent with std::allocator<void> since C++20 (and harmless to do for earlier standards). I'm also explicitly specializing allocator_traits<allocator<void>> so that it doesn't need to use allocator<void>::construct and destroy. Doing that allows those members to be removed, further simplifying allocator<void>. That new explicit specialization can delete the allocate, deallocate and max_size members, which are always ill-formed for allocator<void>. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> libstdc++-v3/ChangeLog: * include/bits/alloc_traits.h (allocator_traits): Add explicit specialization for allocator<void>. Improve doxygen comments. * include/bits/allocator.h (allocator<void>): Restore for the versioned namespace. (allocator<void>::construct, allocator<void>::destroy): Remove. * include/ext/extptr_allocator.h (_Extptr_allocator<void>): Add default constructor and converting constructor.
This commit is contained in:
Jonathan Wakely
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dd3e5859fc
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754fca77e8
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@ -559,6 +559,110 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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{ return __rhs; }
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};
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/// Explicit specialization for std::allocator<void>.
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template<>
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struct allocator_traits<allocator<void>>
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{
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/// The allocator type
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using allocator_type = allocator<void>;
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/// The allocated type
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using value_type = void;
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/// The allocator's pointer type.
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using pointer = void*;
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/// The allocator's const pointer type.
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using const_pointer = const void*;
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/// The allocator's void pointer type.
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using void_pointer = void*;
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/// The allocator's const void pointer type.
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using const_void_pointer = const void*;
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/// The allocator's difference type
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using difference_type = std::ptrdiff_t;
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/// The allocator's size type
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using size_type = std::size_t;
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/// How the allocator is propagated on copy assignment
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using propagate_on_container_copy_assignment = false_type;
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/// How the allocator is propagated on move assignment
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using propagate_on_container_move_assignment = true_type;
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/// How the allocator is propagated on swap
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using propagate_on_container_swap = false_type;
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/// Whether all instances of the allocator type compare equal.
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using is_always_equal = true_type;
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template<typename _Up>
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using rebind_alloc = allocator<_Up>;
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template<typename _Up>
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using rebind_traits = allocator_traits<allocator<_Up>>;
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/// allocate is ill-formed for allocator<void>
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static void*
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allocate(allocator_type&, size_type, const void* = nullptr) = delete;
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/// deallocate is ill-formed for allocator<void>
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static void
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deallocate(allocator_type&, void*, size_type) = delete;
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/**
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* @brief Construct an object of type `_Up`
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* @param __a An allocator.
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* @param __p Pointer to memory of suitable size and alignment for
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* an object of type `_Up`.
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* @param __args Constructor arguments.
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*
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* Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
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* in C++11, C++14 and C++17. Changed in C++20 to call
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* `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
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*/
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template<typename _Up, typename... _Args>
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static _GLIBCXX20_CONSTEXPR void
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construct(allocator_type&, _Up* __p, _Args&&... __args)
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noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
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{
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#if __cplusplus <= 201703L
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::new((void *)__p) _Up(std::forward<_Args>(__args)...);
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#else
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std::construct_at(__p, std::forward<_Args>(__args)...);
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#endif
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}
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/**
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* @brief Destroy an object of type `_Up`
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* @param __a An allocator.
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* @param __p Pointer to the object to destroy
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*
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* Invokes the destructor for `*__p`.
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*/
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template<typename _Up>
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static _GLIBCXX20_CONSTEXPR void
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destroy(allocator_type&, _Up* __p)
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noexcept(is_nothrow_destructible<_Up>::value)
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{ std::_Destroy(__p); }
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/// max_size is ill-formed for allocator<void>
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static size_type
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max_size(const allocator_type&) = delete;
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/**
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* @brief Obtain an allocator to use when copying a container.
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* @param __rhs An allocator.
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* @return `__rhs`
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*/
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static _GLIBCXX20_CONSTEXPR allocator_type
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select_on_container_copy_construction(const allocator_type& __rhs)
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{ return __rhs; }
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};
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#if __cplusplus < 201703L
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template<typename _Alloc>
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inline void
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@ -61,12 +61,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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*/
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// Since C++20 the primary template should be used for allocator<void>,
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// but then it would have a non-trivial default ctor and dtor, which
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// would be an ABI change. So C++20 still uses the allocator<void> explicit
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// specialization, with the historical ABI properties, but with the same
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// members that are present in the primary template.
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// but then it would have a non-trivial default ctor and dtor for C++20,
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// but trivial for C++98-17, which would be an ABI incompatibiliy between
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// different standard dialects. So C++20 still uses the allocator<void>
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// explicit specialization, with the historical ABI properties, but with
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// the same members that are present in the primary template.
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#if ! _GLIBCXX_INLINE_VERSION
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/// allocator<void> specialization.
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template<>
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class allocator<void>
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@ -77,7 +77,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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typedef ptrdiff_t difference_type;
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#if __cplusplus <= 201703L
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// These were removed for C++20.
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// These were removed for C++20, allocator_traits does the right thing.
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typedef void* pointer;
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typedef const void* const_pointer;
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@ -96,7 +96,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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= true_type;
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#if __cplusplus >= 202002L
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// As noted above, these members are present for C++20 to provide the
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// same API as the primary template, but still trivial as in pre-C++20.
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allocator() = default;
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~allocator() = default;
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template<typename _Up>
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constexpr
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@ -105,28 +108,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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// No allocate member because it's ill-formed by LWG 3307.
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// No deallocate member because it would be undefined to call it
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// with any pointer which wasn't obtained from allocate.
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#else // ! C++20
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private:
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// This uses construct and destroy in C++11/14/17 modes.
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friend allocator_traits<allocator<void>>;
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template<typename _Up, typename... _Args>
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void
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construct(_Up* __p, _Args&&... __args)
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noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
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{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
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template<typename _Up>
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void
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destroy(_Up* __p)
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noexcept(std::is_nothrow_destructible<_Up>::value)
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{ __p->~_Up(); }
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#endif // C++17
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#endif // C++20
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#endif // C++11
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};
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#endif // ! _GLIBCXX_INLINE_VERSION
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/**
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* @brief The @a standard allocator, as per C++03 [20.4.1].
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@ -212,7 +196,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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return;
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}
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#endif
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__allocator_base<_Tp>::deallocate(__p, __n);
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__allocator_base<_Tp>::deallocate(__p, __n);
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}
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#endif // C++20
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@ -176,6 +176,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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typedef _Pointer_adapter<_Relative_pointer_impl<const void> >
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const_pointer;
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_ExtPtr_allocator() { }
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template<typename _Up>
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_ExtPtr_allocator(const _ExtPtr_allocator<_Up>&) { }
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template<typename _Up>
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struct rebind
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{ typedef _ExtPtr_allocator<_Up> other; };
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