diff options
Diffstat (limited to 'abseil-cpp/absl/memory/memory.h')
| -rw-r--r-- | abseil-cpp/absl/memory/memory.h | 473 |
1 files changed, 26 insertions, 447 deletions
diff --git a/abseil-cpp/absl/memory/memory.h b/abseil-cpp/absl/memory/memory.h index 2b5ff62..3508135 100644 --- a/abseil-cpp/absl/memory/memory.h +++ b/abseil-cpp/absl/memory/memory.h @@ -75,32 +75,6 @@ std::unique_ptr<T> WrapUnique(T* ptr) { return std::unique_ptr<T>(ptr); } -namespace memory_internal { - -// Traits to select proper overload and return type for `absl::make_unique<>`. -template <typename T> -struct MakeUniqueResult { - using scalar = std::unique_ptr<T>; -}; -template <typename T> -struct MakeUniqueResult<T[]> { - using array = std::unique_ptr<T[]>; -}; -template <typename T, size_t N> -struct MakeUniqueResult<T[N]> { - using invalid = void; -}; - -} // namespace memory_internal - -// gcc 4.8 has __cplusplus at 201301 but the libstdc++ shipped with it doesn't -// define make_unique. Other supported compilers either just define __cplusplus -// as 201103 but have make_unique (msvc), or have make_unique whenever -// __cplusplus > 201103 (clang). -#if (__cplusplus > 201103L || defined(_MSC_VER)) && \ - !(defined(__GLIBCXX__) && !defined(__cpp_lib_make_unique)) -using std::make_unique; -#else // ----------------------------------------------------------------------------- // Function Template: make_unique<T>() // ----------------------------------------------------------------------------- @@ -109,82 +83,18 @@ using std::make_unique; // during the construction process. `absl::make_unique<>` also avoids redundant // type declarations, by avoiding the need to explicitly use the `new` operator. // -// This implementation of `absl::make_unique<>` is designed for C++11 code and -// will be replaced in C++14 by the equivalent `std::make_unique<>` abstraction. -// `absl::make_unique<>` is designed to be 100% compatible with -// `std::make_unique<>` so that the eventual migration will involve a simple -// rename operation. +// https://en.cppreference.com/w/cpp/memory/unique_ptr/make_unique // // For more background on why `std::unique_ptr<T>(new T(a,b))` is problematic, // see Herb Sutter's explanation on // (Exception-Safe Function Calls)[https://herbsutter.com/gotw/_102/]. // (In general, reviewers should treat `new T(a,b)` with scrutiny.) // -// Example usage: -// -// auto p = make_unique<X>(args...); // 'p' is a std::unique_ptr<X> -// auto pa = make_unique<X[]>(5); // 'pa' is a std::unique_ptr<X[]> -// -// Three overloads of `absl::make_unique` are required: -// -// - For non-array T: -// -// Allocates a T with `new T(std::forward<Args> args...)`, -// forwarding all `args` to T's constructor. -// Returns a `std::unique_ptr<T>` owning that object. -// -// - For an array of unknown bounds T[]: -// -// `absl::make_unique<>` will allocate an array T of type U[] with -// `new U[n]()` and return a `std::unique_ptr<U[]>` owning that array. -// -// Note that 'U[n]()' is different from 'U[n]', and elements will be -// value-initialized. Note as well that `std::unique_ptr` will perform its -// own destruction of the array elements upon leaving scope, even though -// the array [] does not have a default destructor. -// -// NOTE: an array of unknown bounds T[] may still be (and often will be) -// initialized to have a size, and will still use this overload. E.g: -// -// auto my_array = absl::make_unique<int[]>(10); -// -// - For an array of known bounds T[N]: -// -// `absl::make_unique<>` is deleted (like with `std::make_unique<>`) as -// this overload is not useful. -// -// NOTE: an array of known bounds T[N] is not considered a useful -// construction, and may cause undefined behavior in templates. E.g: -// -// auto my_array = absl::make_unique<int[10]>(); -// -// In those cases, of course, you can still use the overload above and -// simply initialize it to its desired size: -// -// auto my_array = absl::make_unique<int[]>(10); - -// `absl::make_unique` overload for non-array types. -template <typename T, typename... Args> -typename memory_internal::MakeUniqueResult<T>::scalar make_unique( - Args&&... args) { - return std::unique_ptr<T>(new T(std::forward<Args>(args)...)); -} - -// `absl::make_unique` overload for an array T[] of unknown bounds. -// The array allocation needs to use the `new T[size]` form and cannot take -// element constructor arguments. The `std::unique_ptr` will manage destructing -// these array elements. -template <typename T> -typename memory_internal::MakeUniqueResult<T>::array make_unique(size_t n) { - return std::unique_ptr<T>(new typename absl::remove_extent_t<T>[n]()); -} - -// `absl::make_unique` overload for an array T[N] of known bounds. -// This construction will be rejected. -template <typename T, typename... Args> -typename memory_internal::MakeUniqueResult<T>::invalid make_unique( - Args&&... /* args */) = delete; -#endif +// Historical note: Abseil once provided a C++11 compatible implementation of +// the C++14's `std::make_unique`. Now that C++11 support has been sunsetted, +// `absl::make_unique` simply uses the STL-provided implementation. New code +// should use `std::make_unique`. +using std::make_unique; // ----------------------------------------------------------------------------- // Function Template: RawPtr() @@ -248,6 +158,26 @@ std::weak_ptr<T> WeakenPtr(const std::shared_ptr<T>& ptr) { return std::weak_ptr<T>(ptr); } +// ----------------------------------------------------------------------------- +// Class Template: pointer_traits +// ----------------------------------------------------------------------------- +// +// Historical note: Abseil once provided an implementation of +// `std::pointer_traits` for platforms that had not yet provided it. Those +// platforms are no longer supported. New code should simply use +// `std::pointer_traits`. +using std::pointer_traits; + +// ----------------------------------------------------------------------------- +// Class Template: allocator_traits +// ----------------------------------------------------------------------------- +// +// Historical note: Abseil once provided an implementation of +// `std::allocator_traits` for platforms that had not yet provided it. Those +// platforms are no longer supported. New code should simply use +// `std::allocator_traits`. +using std::allocator_traits; + namespace memory_internal { // ExtractOr<E, O, D>::type evaluates to E<O> if possible. Otherwise, D. @@ -265,357 +195,6 @@ struct ExtractOr<Extract, Obj, Default, void_t<Extract<Obj>>> { template <template <typename> class Extract, typename Obj, typename Default> using ExtractOrT = typename ExtractOr<Extract, Obj, Default, void>::type; -// Extractors for the features of allocators. -template <typename T> -using GetPointer = typename T::pointer; - -template <typename T> -using GetConstPointer = typename T::const_pointer; - -template <typename T> -using GetVoidPointer = typename T::void_pointer; - -template <typename T> -using GetConstVoidPointer = typename T::const_void_pointer; - -template <typename T> -using GetDifferenceType = typename T::difference_type; - -template <typename T> -using GetSizeType = typename T::size_type; - -template <typename T> -using GetPropagateOnContainerCopyAssignment = - typename T::propagate_on_container_copy_assignment; - -template <typename T> -using GetPropagateOnContainerMoveAssignment = - typename T::propagate_on_container_move_assignment; - -template <typename T> -using GetPropagateOnContainerSwap = typename T::propagate_on_container_swap; - -template <typename T> -using GetIsAlwaysEqual = typename T::is_always_equal; - -template <typename T> -struct GetFirstArg; - -template <template <typename...> class Class, typename T, typename... Args> -struct GetFirstArg<Class<T, Args...>> { - using type = T; -}; - -template <typename Ptr, typename = void> -struct ElementType { - using type = typename GetFirstArg<Ptr>::type; -}; - -template <typename T> -struct ElementType<T, void_t<typename T::element_type>> { - using type = typename T::element_type; -}; - -template <typename T, typename U> -struct RebindFirstArg; - -template <template <typename...> class Class, typename T, typename... Args, - typename U> -struct RebindFirstArg<Class<T, Args...>, U> { - using type = Class<U, Args...>; -}; - -template <typename T, typename U, typename = void> -struct RebindPtr { - using type = typename RebindFirstArg<T, U>::type; -}; - -template <typename T, typename U> -struct RebindPtr<T, U, void_t<typename T::template rebind<U>>> { - using type = typename T::template rebind<U>; -}; - -template <typename T, typename U> -constexpr bool HasRebindAlloc(...) { - return false; -} - -template <typename T, typename U> -constexpr bool HasRebindAlloc(typename T::template rebind<U>::other*) { - return true; -} - -template <typename T, typename U, bool = HasRebindAlloc<T, U>(nullptr)> -struct RebindAlloc { - using type = typename RebindFirstArg<T, U>::type; -}; - -template <typename T, typename U> -struct RebindAlloc<T, U, true> { - using type = typename T::template rebind<U>::other; -}; - -} // namespace memory_internal - -// ----------------------------------------------------------------------------- -// Class Template: pointer_traits -// ----------------------------------------------------------------------------- -// -// An implementation of C++11's std::pointer_traits. -// -// Provided for portability on toolchains that have a working C++11 compiler, -// but the standard library is lacking in C++11 support. For example, some -// version of the Android NDK. -// - -template <typename Ptr> -struct pointer_traits { - using pointer = Ptr; - - // element_type: - // Ptr::element_type if present. Otherwise T if Ptr is a template - // instantiation Template<T, Args...> - using element_type = typename memory_internal::ElementType<Ptr>::type; - - // difference_type: - // Ptr::difference_type if present, otherwise std::ptrdiff_t - using difference_type = - memory_internal::ExtractOrT<memory_internal::GetDifferenceType, Ptr, - std::ptrdiff_t>; - - // rebind: - // Ptr::rebind<U> if exists, otherwise Template<U, Args...> if Ptr is a - // template instantiation Template<T, Args...> - template <typename U> - using rebind = typename memory_internal::RebindPtr<Ptr, U>::type; - - // pointer_to: - // Calls Ptr::pointer_to(r) - static pointer pointer_to(element_type& r) { // NOLINT(runtime/references) - return Ptr::pointer_to(r); - } -}; - -// Specialization for T*. -template <typename T> -struct pointer_traits<T*> { - using pointer = T*; - using element_type = T; - using difference_type = std::ptrdiff_t; - - template <typename U> - using rebind = U*; - - // pointer_to: - // Calls std::addressof(r) - static pointer pointer_to( - element_type& r) noexcept { // NOLINT(runtime/references) - return std::addressof(r); - } -}; - -// ----------------------------------------------------------------------------- -// Class Template: allocator_traits -// ----------------------------------------------------------------------------- -// -// A C++11 compatible implementation of C++17's std::allocator_traits. -// -#if __cplusplus >= 201703L -using std::allocator_traits; -#else // __cplusplus >= 201703L -template <typename Alloc> -struct allocator_traits { - using allocator_type = Alloc; - - // value_type: - // Alloc::value_type - using value_type = typename Alloc::value_type; - - // pointer: - // Alloc::pointer if present, otherwise value_type* - using pointer = memory_internal::ExtractOrT<memory_internal::GetPointer, - Alloc, value_type*>; - - // const_pointer: - // Alloc::const_pointer if present, otherwise - // absl::pointer_traits<pointer>::rebind<const value_type> - using const_pointer = - memory_internal::ExtractOrT<memory_internal::GetConstPointer, Alloc, - typename absl::pointer_traits<pointer>:: - template rebind<const value_type>>; - - // void_pointer: - // Alloc::void_pointer if present, otherwise - // absl::pointer_traits<pointer>::rebind<void> - using void_pointer = memory_internal::ExtractOrT< - memory_internal::GetVoidPointer, Alloc, - typename absl::pointer_traits<pointer>::template rebind<void>>; - - // const_void_pointer: - // Alloc::const_void_pointer if present, otherwise - // absl::pointer_traits<pointer>::rebind<const void> - using const_void_pointer = memory_internal::ExtractOrT< - memory_internal::GetConstVoidPointer, Alloc, - typename absl::pointer_traits<pointer>::template rebind<const void>>; - - // difference_type: - // Alloc::difference_type if present, otherwise - // absl::pointer_traits<pointer>::difference_type - using difference_type = memory_internal::ExtractOrT< - memory_internal::GetDifferenceType, Alloc, - typename absl::pointer_traits<pointer>::difference_type>; - - // size_type: - // Alloc::size_type if present, otherwise - // std::make_unsigned<difference_type>::type - using size_type = memory_internal::ExtractOrT< - memory_internal::GetSizeType, Alloc, - typename std::make_unsigned<difference_type>::type>; - - // propagate_on_container_copy_assignment: - // Alloc::propagate_on_container_copy_assignment if present, otherwise - // std::false_type - using propagate_on_container_copy_assignment = memory_internal::ExtractOrT< - memory_internal::GetPropagateOnContainerCopyAssignment, Alloc, - std::false_type>; - - // propagate_on_container_move_assignment: - // Alloc::propagate_on_container_move_assignment if present, otherwise - // std::false_type - using propagate_on_container_move_assignment = memory_internal::ExtractOrT< - memory_internal::GetPropagateOnContainerMoveAssignment, Alloc, - std::false_type>; - - // propagate_on_container_swap: - // Alloc::propagate_on_container_swap if present, otherwise std::false_type - using propagate_on_container_swap = - memory_internal::ExtractOrT<memory_internal::GetPropagateOnContainerSwap, - Alloc, std::false_type>; - - // is_always_equal: - // Alloc::is_always_equal if present, otherwise std::is_empty<Alloc>::type - using is_always_equal = - memory_internal::ExtractOrT<memory_internal::GetIsAlwaysEqual, Alloc, - typename std::is_empty<Alloc>::type>; - - // rebind_alloc: - // Alloc::rebind<T>::other if present, otherwise Alloc<T, Args> if this Alloc - // is Alloc<U, Args> - template <typename T> - using rebind_alloc = typename memory_internal::RebindAlloc<Alloc, T>::type; - - // rebind_traits: - // absl::allocator_traits<rebind_alloc<T>> - template <typename T> - using rebind_traits = absl::allocator_traits<rebind_alloc<T>>; - - // allocate(Alloc& a, size_type n): - // Calls a.allocate(n) - static pointer allocate(Alloc& a, // NOLINT(runtime/references) - size_type n) { - return a.allocate(n); - } - - // allocate(Alloc& a, size_type n, const_void_pointer hint): - // Calls a.allocate(n, hint) if possible. - // If not possible, calls a.allocate(n) - static pointer allocate(Alloc& a, size_type n, // NOLINT(runtime/references) - const_void_pointer hint) { - return allocate_impl(0, a, n, hint); - } - - // deallocate(Alloc& a, pointer p, size_type n): - // Calls a.deallocate(p, n) - static void deallocate(Alloc& a, pointer p, // NOLINT(runtime/references) - size_type n) { - a.deallocate(p, n); - } - - // construct(Alloc& a, T* p, Args&&... args): - // Calls a.construct(p, std::forward<Args>(args)...) if possible. - // If not possible, calls - // ::new (static_cast<void*>(p)) T(std::forward<Args>(args)...) - template <typename T, typename... Args> - static void construct(Alloc& a, T* p, // NOLINT(runtime/references) - Args&&... args) { - construct_impl(0, a, p, std::forward<Args>(args)...); - } - - // destroy(Alloc& a, T* p): - // Calls a.destroy(p) if possible. If not possible, calls p->~T(). - template <typename T> - static void destroy(Alloc& a, T* p) { // NOLINT(runtime/references) - destroy_impl(0, a, p); - } - - // max_size(const Alloc& a): - // Returns a.max_size() if possible. If not possible, returns - // std::numeric_limits<size_type>::max() / sizeof(value_type) - static size_type max_size(const Alloc& a) { return max_size_impl(0, a); } - - // select_on_container_copy_construction(const Alloc& a): - // Returns a.select_on_container_copy_construction() if possible. - // If not possible, returns a. - static Alloc select_on_container_copy_construction(const Alloc& a) { - return select_on_container_copy_construction_impl(0, a); - } - - private: - template <typename A> - static auto allocate_impl(int, A& a, // NOLINT(runtime/references) - size_type n, const_void_pointer hint) - -> decltype(a.allocate(n, hint)) { - return a.allocate(n, hint); - } - static pointer allocate_impl(char, Alloc& a, // NOLINT(runtime/references) - size_type n, const_void_pointer) { - return a.allocate(n); - } - - template <typename A, typename... Args> - static auto construct_impl(int, A& a, // NOLINT(runtime/references) - Args&&... args) - -> decltype(a.construct(std::forward<Args>(args)...)) { - a.construct(std::forward<Args>(args)...); - } - - template <typename T, typename... Args> - static void construct_impl(char, Alloc&, T* p, Args&&... args) { - ::new (static_cast<void*>(p)) T(std::forward<Args>(args)...); - } - - template <typename A, typename T> - static auto destroy_impl(int, A& a, // NOLINT(runtime/references) - T* p) -> decltype(a.destroy(p)) { - a.destroy(p); - } - template <typename T> - static void destroy_impl(char, Alloc&, T* p) { - p->~T(); - } - - template <typename A> - static auto max_size_impl(int, const A& a) -> decltype(a.max_size()) { - return a.max_size(); - } - static size_type max_size_impl(char, const Alloc&) { - return (std::numeric_limits<size_type>::max)() / sizeof(value_type); - } - - template <typename A> - static auto select_on_container_copy_construction_impl(int, const A& a) - -> decltype(a.select_on_container_copy_construction()) { - return a.select_on_container_copy_construction(); - } - static Alloc select_on_container_copy_construction_impl(char, - const Alloc& a) { - return a; - } -}; -#endif // __cplusplus >= 201703L - -namespace memory_internal { - // This template alias transforms Alloc::is_nothrow into a metafunction with // Alloc as a parameter so it can be used with ExtractOrT<>. template <typename Alloc> |