1 /* 2 * Copyright 2019 Google LLC 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef FCP_BASE_ERROR_H_ 18 #define FCP_BASE_ERROR_H_ 19 20 namespace fcp { 21 22 // An Error indicates that something went wrong. Errors carry data, but are 23 // opaque to most code; error data is intended to support diagnostics, but not 24 // program behavior. 25 // 26 // Code should be written such that values are turned into opaque Errors only 27 // after they are judged to be problematic (something went wrong). If one finds 28 // the need to inspect the "reason" for an Error, some earlier (non-error) value 29 // should be used instead. 30 // 31 // Errors are typically returned inside of a Result. 32 class Error { 33 // TODO(team): Make it possible to get a stack trace from a tracing span 34 // and save this in the error. 35 public: 36 class ConstructorAccess { 37 template <class FlatBufferTable, class... Arg> 38 friend Error TraceError(Arg&&... args); 39 40 private: 41 constexpr ConstructorAccess() = default; 42 constexpr ConstructorAccess(const ConstructorAccess&) = default; 43 }; 44 45 // Error is copyable but not trivially constructible. 46 // Use global TraceError() function to construct an Error. Error(ConstructorAccess)47 explicit constexpr Error(ConstructorAccess) {} 48 Error(const Error&) = default; 49 }; 50 51 } // namespace fcp 52 53 #endif // FCP_BASE_ERROR_H_ 54