1 // Copyright 2018 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // ----------------------------------------------------------------------------- 16 // bad_variant_access.h 17 // ----------------------------------------------------------------------------- 18 // 19 // This header file defines the `absl::bad_variant_access` type. 20 21 #ifndef ABSL_TYPES_BAD_VARIANT_ACCESS_H_ 22 #define ABSL_TYPES_BAD_VARIANT_ACCESS_H_ 23 24 #include <stdexcept> 25 26 #include "absl/base/config.h" 27 28 #ifdef ABSL_USES_STD_VARIANT 29 30 #include <variant> 31 32 namespace absl { 33 ABSL_NAMESPACE_BEGIN 34 using std::bad_variant_access; 35 ABSL_NAMESPACE_END 36 } // namespace absl 37 38 #else // ABSL_USES_STD_VARIANT 39 40 namespace absl { 41 ABSL_NAMESPACE_BEGIN 42 43 // ----------------------------------------------------------------------------- 44 // bad_variant_access 45 // ----------------------------------------------------------------------------- 46 // 47 // An `absl::bad_variant_access` type is an exception type that is thrown in 48 // the following cases: 49 // 50 // * Calling `absl::get(absl::variant) with an index or type that does not 51 // match the currently selected alternative type 52 // * Calling `absl::visit on an `absl::variant` that is in the 53 // `variant::valueless_by_exception` state. 54 // 55 // Example: 56 // 57 // absl::variant<int, std::string> v; 58 // v = 1; 59 // try { 60 // absl::get<std::string>(v); 61 // } catch(const absl::bad_variant_access& e) { 62 // std::cout << "Bad variant access: " << e.what() << '\n'; 63 // } 64 class bad_variant_access : public std::exception { 65 public: 66 bad_variant_access() noexcept = default; 67 ~bad_variant_access() override; 68 const char* what() const noexcept override; 69 }; 70 71 namespace variant_internal { 72 73 [[noreturn]] void ThrowBadVariantAccess(); 74 [[noreturn]] void Rethrow(); 75 76 } // namespace variant_internal 77 ABSL_NAMESPACE_END 78 } // namespace absl 79 80 #endif // ABSL_USES_STD_VARIANT 81 82 #endif // ABSL_TYPES_BAD_VARIANT_ACCESS_H_ 83