diff --git a/absl/types/any.h b/absl/types/any.h index a51dea110..fe1048188 100644 --- a/absl/types/any.h +++ b/absl/types/any.h @@ -94,23 +94,20 @@ namespace absl { namespace any_internal { -// FastTypeId() 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 -inline size_t FastTypeId() { - static_assert(sizeof(char*) <= sizeof(size_t), - "ptr size too large for size_t"); +template +struct TypeTag { + constexpr static char dummy_var = 0; +}; - // This static variable isn't actually used, only its address, so there are - // no concurrency issues. - static char dummy_var; - return reinterpret_cast(&dummy_var); +template +constexpr char TypeTag::dummy_var; + +// FastTypeId() 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 +constexpr inline const void* FastTypeId() { + return &TypeTag::dummy_var; } } // namespace any_internal @@ -382,10 +379,20 @@ class any { public: virtual ~ObjInterface() = default; virtual std::unique_ptr 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 + + // 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. + size_t type_id() const noexcept { + static_assert(sizeof(void*) <= sizeof(size_t), + "ptr size too large for size_t"); + return reinterpret_cast(ObjTypeId()); + } }; // Hold a value of some queryable type, with an ability to Clone it. @@ -400,7 +407,7 @@ class any { return std::unique_ptr(new Obj(in_place, value)); } - size_t type_id() const noexcept final { return IdForType(); } + const void* ObjTypeId() const noexcept final { return IdForType(); } #if ABSL_ANY_DETAIL_HAS_RTTI const std::type_info& Type() const noexcept final { return typeid(T); } @@ -415,7 +422,7 @@ class any { } template - 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::type>::type; @@ -423,8 +430,9 @@ class any { return any_internal::FastTypeId(); } - size_t GetObjTypeId() const { - return obj_ == nullptr ? any_internal::FastTypeId() : obj_->type_id(); + const void* GetObjTypeId() const { + return obj_ == nullptr ? any_internal::FastTypeId() + : obj_->ObjTypeId(); } // `absl::any` nonmember functions //