usage.cc (2356B)
1 // 2 // Copyright 2019 The Abseil Authors. 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 // https://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 #include "absl/flags/usage.h" 16 17 #include <stdlib.h> 18 19 #include <string> 20 21 #include "absl/base/attributes.h" 22 #include "absl/base/config.h" 23 #include "absl/base/const_init.h" 24 #include "absl/base/internal/raw_logging.h" 25 #include "absl/base/thread_annotations.h" 26 #include "absl/flags/internal/usage.h" 27 #include "absl/strings/string_view.h" 28 #include "absl/synchronization/mutex.h" 29 30 namespace absl { 31 ABSL_NAMESPACE_BEGIN 32 namespace flags_internal { 33 namespace { 34 ABSL_CONST_INIT absl::Mutex usage_message_guard(absl::kConstInit); 35 ABSL_CONST_INIT std::string* program_usage_message 36 ABSL_GUARDED_BY(usage_message_guard) = nullptr; 37 } // namespace 38 } // namespace flags_internal 39 40 // -------------------------------------------------------------------- 41 // Sets the "usage" message to be used by help reporting routines. 42 void SetProgramUsageMessage(absl::string_view new_usage_message) { 43 absl::MutexLock l(&flags_internal::usage_message_guard); 44 45 if (flags_internal::program_usage_message != nullptr) { 46 ABSL_INTERNAL_LOG(FATAL, "SetProgramUsageMessage() called twice."); 47 std::exit(1); 48 } 49 50 flags_internal::program_usage_message = new std::string(new_usage_message); 51 } 52 53 // -------------------------------------------------------------------- 54 // Returns the usage message set by SetProgramUsageMessage(). 55 // Note: We able to return string_view here only because calling 56 // SetProgramUsageMessage twice is prohibited. 57 absl::string_view ProgramUsageMessage() { 58 absl::MutexLock l(&flags_internal::usage_message_guard); 59 60 return flags_internal::program_usage_message != nullptr 61 ? absl::string_view(*flags_internal::program_usage_message) 62 : "Warning: SetProgramUsageMessage() never called"; 63 } 64 65 ABSL_NAMESPACE_END 66 } // namespace absl