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-rw-r--r--absl/flags/usage.cc56
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+//
+// Copyright 2019 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.
+#include "absl/flags/usage.h"
+
+#include <string>
+
+#include "absl/flags/internal/usage.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+namespace flags_internal {
+namespace {
+ABSL_CONST_INIT absl::Mutex usage_message_guard(absl::kConstInit);
+ABSL_CONST_INIT std::string* program_usage_message
+ GUARDED_BY(usage_message_guard) = nullptr;
+} // namespace
+} // namespace flags_internal
+
+// --------------------------------------------------------------------
+// Sets the "usage" message to be used by help reporting routines.
+void SetProgramUsageMessage(absl::string_view new_usage_message) {
+ absl::MutexLock l(&flags_internal::usage_message_guard);
+
+ if (flags_internal::program_usage_message != nullptr) {
+ ABSL_INTERNAL_LOG(FATAL, "SetProgramUsageMessage() called twice.");
+ std::exit(1);
+ }
+
+ flags_internal::program_usage_message = new std::string(new_usage_message);
+}
+
+// --------------------------------------------------------------------
+// Returns the usage message set by SetProgramUsageMessage().
+// Note: We able to return string_view here only because calling
+// SetProgramUsageMessage twice is prohibited.
+absl::string_view ProgramUsageMessage() {
+ absl::MutexLock l(&flags_internal::usage_message_guard);
+
+ return flags_internal::program_usage_message != nullptr
+ ? absl::string_view(*flags_internal::program_usage_message)
+ : "Warning: SetProgramUsageMessage() never called";
+}
+
+} // namespace absl