diff options
| -rw-r--r-- | absl/types/any.h | 39 |
1 files changed, 18 insertions, 21 deletions
diff --git a/absl/types/any.h b/absl/types/any.h index a51dea110d0f..2e7bf21f55f6 100644 --- a/absl/types/any.h +++ b/absl/types/any.h @@ -94,23 +94,20 @@ namespace absl { namespace any_internal { -// FastTypeId<Type>() evaluates at compile/link-time to a unique integer for the -// passed in type. Their values are neither contiguous nor small, making them -// unfit for using as an index into a vector, but a good match for keys into -// maps or straight up comparisons. -// Note that on 64-bit (unix) systems size_t is 64-bit while int is 32-bit and -// the compiler will happily and quietly assign such a 64-bit value to a -// 32-bit integer. While a client should never do that it SHOULD still be safe, -// assuming the BSS segment doesn't span more than 4GiB. +template <typename Type> +struct TypeTag { + constexpr static char dummy_var = 0; +}; + +template <typename Type> +constexpr char TypeTag<Type>::dummy_var; + +// FastTypeId<Type>() evaluates at compile/link-time to a unique pointer for the +// passed in type. These are meant to be good match for keys into maps or +// straight up comparisons. template<typename Type> -inline size_t FastTypeId() { - static_assert(sizeof(char*) <= sizeof(size_t), - "ptr size too large for size_t"); - - // This static variable isn't actually used, only its address, so there are - // no concurrency issues. - static char dummy_var; - return reinterpret_cast<size_t>(&dummy_var); +constexpr inline const void* FastTypeId() { + return &TypeTag<Type>::dummy_var; } } // namespace any_internal @@ -382,7 +379,7 @@ class any { public: virtual ~ObjInterface() = default; virtual std::unique_ptr<ObjInterface> Clone() const = 0; - virtual size_t type_id() const noexcept = 0; + virtual const void* ObjTypeId() const noexcept = 0; #if ABSL_ANY_DETAIL_HAS_RTTI virtual const std::type_info& Type() const noexcept = 0; #endif // ABSL_ANY_DETAIL_HAS_RTTI @@ -400,7 +397,7 @@ class any { return std::unique_ptr<ObjInterface>(new Obj(in_place, value)); } - size_t type_id() const noexcept final { return IdForType<T>(); } + const void* ObjTypeId() const noexcept final { return IdForType<T>(); } #if ABSL_ANY_DETAIL_HAS_RTTI const std::type_info& Type() const noexcept final { return typeid(T); } @@ -415,7 +412,7 @@ class any { } template <typename T> - static size_t IdForType() { + constexpr static const void* IdForType() { // Note: This type dance is to make the behavior consistent with typeid. using NormalizedType = typename std::remove_cv<typename std::remove_reference<T>::type>::type; @@ -423,8 +420,8 @@ class any { return any_internal::FastTypeId<NormalizedType>(); } - size_t GetObjTypeId() const { - return obj_ == nullptr ? any_internal::FastTypeId<void>() : obj_->type_id(); + const void* GetObjTypeId() const { + return obj_ ? obj_->ObjTypeId() : any_internal::FastTypeId<void>(); } // `absl::any` nonmember functions // |