| // Copyright 2022 The Abseil Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| // ----------------------------------------------------------------------------- |
| // File: log/internal/nullstream.h |
| // ----------------------------------------------------------------------------- |
| // |
| // Classes `NullStream`, `NullStreamMaybeFatal ` and `NullStreamFatal` |
| // implement a subset of the `LogMessage` API and are used instead when logging |
| // of messages has been disabled. |
| |
| #ifndef ABSL_LOG_INTERNAL_NULLSTREAM_H_ |
| #define ABSL_LOG_INTERNAL_NULLSTREAM_H_ |
| |
| #ifdef _WIN32 |
| #include <cstdlib> |
| #else |
| #include <unistd.h> |
| #endif |
| #include <ios> |
| #include <ostream> |
| |
| #include "absl/base/attributes.h" |
| #include "absl/base/config.h" |
| #include "absl/base/log_severity.h" |
| #include "absl/strings/string_view.h" |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| namespace log_internal { |
| |
| // A `NullStream` implements the API of `LogMessage` (a few methods and |
| // `operator<<`) but does nothing. All methods are defined inline so the |
| // compiler can eliminate the whole instance and discard anything that's |
| // streamed in. |
| class NullStream { |
| public: |
| NullStream& AtLocation(absl::string_view, int) { return *this; } |
| template <typename SourceLocationType> |
| NullStream& AtLocation(SourceLocationType) { |
| return *this; |
| } |
| NullStream& NoPrefix() { return *this; } |
| NullStream& WithVerbosity(int) { return *this; } |
| template <typename TimeType> |
| NullStream& WithTimestamp(TimeType) { |
| return *this; |
| } |
| template <typename Tid> |
| NullStream& WithThreadID(Tid) { |
| return *this; |
| } |
| template <typename LogEntryType> |
| NullStream& WithMetadataFrom(const LogEntryType&) { |
| return *this; |
| } |
| NullStream& WithPerror() { return *this; } |
| template <typename LogSinkType> |
| NullStream& ToSinkAlso(LogSinkType*) { |
| return *this; |
| } |
| template <typename LogSinkType> |
| NullStream& ToSinkOnly(LogSinkType*) { |
| return *this; |
| } |
| template <typename LogSinkType> |
| NullStream& OutputToSink(LogSinkType*, bool) { |
| return *this; |
| } |
| NullStream& InternalStream() { return *this; } |
| }; |
| template <typename T> |
| inline NullStream& operator<<(NullStream& str, const T&) { |
| return str; |
| } |
| inline NullStream& operator<<(NullStream& str, |
| std::ostream& (*)(std::ostream& os)) { |
| return str; |
| } |
| inline NullStream& operator<<(NullStream& str, |
| std::ios_base& (*)(std::ios_base& os)) { |
| return str; |
| } |
| |
| // `NullStreamMaybeFatal` implements the process termination semantics of |
| // `LogMessage`, which is used for `DFATAL` severity and expression-defined |
| // severity e.g. `LOG(LEVEL(HowBadIsIt()))`. Like `LogMessage`, it terminates |
| // the process when destroyed if the passed-in severity equals `FATAL`. |
| class NullStreamMaybeFatal final : public NullStream { |
| public: |
| explicit NullStreamMaybeFatal(absl::LogSeverity severity) |
| : fatal_(severity == absl::LogSeverity::kFatal) {} |
| ~NullStreamMaybeFatal() { |
| if (fatal_) { |
| _exit(1); |
| } |
| } |
| |
| private: |
| bool fatal_; |
| }; |
| |
| // `NullStreamFatal` implements the process termination semantics of |
| // `LogMessageFatal`, which means it always terminates the process. `DFATAL` |
| // and expression-defined severity use `NullStreamMaybeFatal` above. |
| class NullStreamFatal final : public NullStream { |
| public: |
| NullStreamFatal() = default; |
| // ABSL_ATTRIBUTE_NORETURN doesn't seem to work on destructors with msvc, so |
| // disable msvc's warning about the d'tor never returning. |
| #if defined(_MSC_VER) && !defined(__clang__) |
| #pragma warning(push) |
| #pragma warning(disable : 4722) |
| #endif |
| ABSL_ATTRIBUTE_NORETURN ~NullStreamFatal() { _exit(1); } |
| #if defined(_MSC_VER) && !defined(__clang__) |
| #pragma warning(pop) |
| #endif |
| }; |
| |
| } // namespace log_internal |
| ABSL_NAMESPACE_END |
| } // namespace absl |
| |
| #endif // ABSL_LOG_INTERNAL_GLOBALS_H_ |