abseil-cpp/absl/flags/usage_config.cc

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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_config.h"
 
#include <functional>
#include <iostream>
#include <string>
 
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/const_init.h"
#include "absl/base/thread_annotations.h"
#include "absl/flags/internal/path_util.h"
#include "absl/flags/internal/program_name.h"
#include "absl/strings/match.h"
#include "absl/strings/string_view.h"
#include "absl/strings/strip.h"
#include "absl/synchronization/mutex.h"
 
extern "C" {
 
// Additional report of fatal usage error message before we std::exit. Error is
// fatal if is_fatal argument to ReportUsageError is true.
ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(
    AbslInternalReportFatalUsageError)(absl::string_view) {}
 
}  // extern "C"
 
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
 
namespace {
 
// --------------------------------------------------------------------
// Returns true if flags defined in the filename should be reported with
// -helpshort flag.
 
bool ContainsHelpshortFlags(absl::string_view filename) {
  // By default we only want flags in binary's main. We expect the main
  // routine to reside in <program>.cc or <program>-main.cc or
  // <program>_main.cc, where the <program> is the name of the binary
  // (without .exe on Windows).
  auto suffix = flags_internal::Basename(filename);
  auto program_name = flags_internal::ShortProgramInvocationName();
  absl::string_view program_name_ref = program_name;
#if defined(_WIN32)
  absl::ConsumeSuffix(&program_name_ref, ".exe");
#endif
  if (!absl::ConsumePrefix(&suffix, program_name_ref))
    return false;
  return absl::StartsWith(suffix, ".") || absl::StartsWith(suffix, "-main.") ||
         absl::StartsWith(suffix, "_main.");
}
 
// --------------------------------------------------------------------
// Returns true if flags defined in the filename should be reported with
// -helppackage flag.
 
bool ContainsHelppackageFlags(absl::string_view filename) {
  // TODO(rogeeff): implement properly when registry is available.
  return ContainsHelpshortFlags(filename);
}
 
// --------------------------------------------------------------------
// Generates program version information into supplied output.
 
std::string VersionString() {
  std::string version_str(flags_internal::ShortProgramInvocationName());
 
  version_str += "\n";
 
#if !defined(NDEBUG)
  version_str += "Debug build (NDEBUG not #defined)\n";
#endif
 
  return version_str;
}
 
// --------------------------------------------------------------------
// Normalizes the filename specific to the build system/filesystem used.
 
std::string NormalizeFilename(absl::string_view filename) {
  // Skip any leading slashes
  auto pos = filename.find_first_not_of("\\/");
  if (pos == absl::string_view::npos) return "";
 
  filename.remove_prefix(pos);
  return std::string(filename);
}
 
// --------------------------------------------------------------------
 
ABSL_CONST_INIT absl::Mutex custom_usage_config_guard(absl::kConstInit);
ABSL_CONST_INIT FlagsUsageConfig* custom_usage_config
    ABSL_GUARDED_BY(custom_usage_config_guard) = nullptr;
 
}  // namespace
 
FlagsUsageConfig GetUsageConfig() {
  absl::MutexLock l(&custom_usage_config_guard);
 
  if (custom_usage_config) return *custom_usage_config;
 
  FlagsUsageConfig default_config;
  default_config.contains_helpshort_flags = &ContainsHelpshortFlags;
  default_config.contains_help_flags = &ContainsHelppackageFlags;
  default_config.contains_helppackage_flags = &ContainsHelppackageFlags;
  default_config.version_string = &VersionString;
  default_config.normalize_filename = &NormalizeFilename;
 
  return default_config;
}
 
void ReportUsageError(absl::string_view msg, bool is_fatal) {
  std::cerr << "ERROR: " << msg << std::endl;
 
  if (is_fatal) {
    ABSL_INTERNAL_C_SYMBOL(AbslInternalReportFatalUsageError)(msg);
  }
}
 
}  // namespace flags_internal
 
void SetFlagsUsageConfig(FlagsUsageConfig usage_config) {
  absl::MutexLock l(&flags_internal::custom_usage_config_guard);
 
  if (!usage_config.contains_helpshort_flags)
    usage_config.contains_helpshort_flags =
        flags_internal::ContainsHelpshortFlags;
 
  if (!usage_config.contains_help_flags)
    usage_config.contains_help_flags = flags_internal::ContainsHelppackageFlags;
 
  if (!usage_config.contains_helppackage_flags)
    usage_config.contains_helppackage_flags =
        flags_internal::ContainsHelppackageFlags;
 
  if (!usage_config.version_string)
    usage_config.version_string = flags_internal::VersionString;
 
  if (!usage_config.normalize_filename)
    usage_config.normalize_filename = flags_internal::NormalizeFilename;
 
  if (flags_internal::custom_usage_config)
    *flags_internal::custom_usage_config = usage_config;
  else
    flags_internal::custom_usage_config = new FlagsUsageConfig(usage_config);
}
 
ABSL_NAMESPACE_END
}  // namespace absl