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Yao
2024-12-20 17:49:45 +08:00
parent 86b0363ce1
commit 654d456c7d
7011 changed files with 1705926 additions and 7 deletions
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26
Pods/abseil/absl/flags/internal/commandlineflag.cc generated Normal file
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//
// Copyright 2020 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/internal/commandlineflag.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
FlagStateInterface::~FlagStateInterface() = default;
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl

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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.
#ifndef ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
#define ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
#include "absl/base/config.h"
#include "absl/base/internal/fast_type_id.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// An alias for flag fast type id. This value identifies the flag value type
// similarly to typeid(T), without relying on RTTI being available. In most
// cases this id is enough to uniquely identify the flag's value type. In a few
// cases we'll have to resort to using actual RTTI implementation if it is
// available.
using FlagFastTypeId = absl::base_internal::FastTypeIdType;
// Options that control SetCommandLineOptionWithMode.
enum FlagSettingMode {
// update the flag's value unconditionally (can call this multiple times).
SET_FLAGS_VALUE,
// update the flag's value, but *only if* it has not yet been updated
// with SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef".
SET_FLAG_IF_DEFAULT,
// set the flag's default value to this. If the flag has not been updated
// yet (via SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef")
// change the flag's current value to the new default value as well.
SET_FLAGS_DEFAULT
};
// Options that control ParseFrom: Source of a value.
enum ValueSource {
// Flag is being set by value specified on a command line.
kCommandLine,
// Flag is being set by value specified in the code.
kProgrammaticChange,
};
// Handle to FlagState objects. Specific flag state objects will restore state
// of a flag produced this flag state from method CommandLineFlag::SaveState().
class FlagStateInterface {
public:
virtual ~FlagStateInterface();
// Restores the flag originated this object to the saved state.
virtual void Restore() const = 0;
};
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_

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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/internal/flag.h"
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <array>
#include <atomic>
#include <memory>
#include <new>
#include <string>
#include <typeinfo>
#include "absl/base/call_once.h"
#include "absl/base/casts.h"
#include "absl/base/config.h"
#include "absl/base/dynamic_annotations.h"
#include "absl/base/optimization.h"
#include "absl/flags/config.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/flags/usage_config.h"
#include "absl/memory/memory.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// The help message indicating that the commandline flag has been
// 'stripped'. It will not show up when doing "-help" and its
// variants. The flag is stripped if ABSL_FLAGS_STRIP_HELP is set to 1
// before including absl/flags/flag.h
const char kStrippedFlagHelp[] = "\001\002\003\004 (unknown) \004\003\002\001";
namespace {
// Currently we only validate flag values for user-defined flag types.
bool ShouldValidateFlagValue(FlagFastTypeId flag_type_id) {
#define DONT_VALIDATE(T, _) \
if (flag_type_id == base_internal::FastTypeId<T>()) return false;
ABSL_FLAGS_INTERNAL_SUPPORTED_TYPES(DONT_VALIDATE)
#undef DONT_VALIDATE
return true;
}
// RAII helper used to temporarily unlock and relock `absl::Mutex`.
// This is used when we need to ensure that locks are released while
// invoking user supplied callbacks and then reacquired, since callbacks may
// need to acquire these locks themselves.
class MutexRelock {
public:
explicit MutexRelock(absl::Mutex& mu) : mu_(mu) { mu_.Unlock(); }
~MutexRelock() { mu_.Lock(); }
MutexRelock(const MutexRelock&) = delete;
MutexRelock& operator=(const MutexRelock&) = delete;
private:
absl::Mutex& mu_;
};
} // namespace
///////////////////////////////////////////////////////////////////////////////
// Persistent state of the flag data.
class FlagImpl;
class FlagState : public flags_internal::FlagStateInterface {
public:
template <typename V>
FlagState(FlagImpl& flag_impl, const V& v, bool modified,
bool on_command_line, int64_t counter)
: flag_impl_(flag_impl),
value_(v),
modified_(modified),
on_command_line_(on_command_line),
counter_(counter) {}
~FlagState() override {
if (flag_impl_.ValueStorageKind() != FlagValueStorageKind::kAlignedBuffer &&
flag_impl_.ValueStorageKind() != FlagValueStorageKind::kSequenceLocked)
return;
flags_internal::Delete(flag_impl_.op_, value_.heap_allocated);
}
private:
friend class FlagImpl;
// Restores the flag to the saved state.
void Restore() const override {
if (!flag_impl_.RestoreState(*this)) return;
ABSL_INTERNAL_LOG(INFO,
absl::StrCat("Restore saved value of ", flag_impl_.Name(),
" to: ", flag_impl_.CurrentValue()));
}
// Flag and saved flag data.
FlagImpl& flag_impl_;
union SavedValue {
explicit SavedValue(void* v) : heap_allocated(v) {}
explicit SavedValue(int64_t v) : one_word(v) {}
void* heap_allocated;
int64_t one_word;
} value_;
bool modified_;
bool on_command_line_;
int64_t counter_;
};
///////////////////////////////////////////////////////////////////////////////
// Flag implementation, which does not depend on flag value type.
DynValueDeleter::DynValueDeleter(FlagOpFn op_arg) : op(op_arg) {}
void DynValueDeleter::operator()(void* ptr) const {
if (op == nullptr) return;
Delete(op, ptr);
}
void FlagImpl::Init() {
new (&data_guard_) absl::Mutex;
auto def_kind = static_cast<FlagDefaultKind>(def_kind_);
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
alignas(int64_t) std::array<char, sizeof(int64_t)> buf{};
if (def_kind == FlagDefaultKind::kGenFunc) {
(*default_value_.gen_func)(buf.data());
} else {
assert(def_kind != FlagDefaultKind::kDynamicValue);
std::memcpy(buf.data(), &default_value_, Sizeof(op_));
}
if (ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit) {
// We presume here the memory layout of FlagValueAndInitBit struct.
uint8_t initialized = 1;
std::memcpy(buf.data() + Sizeof(op_), &initialized,
sizeof(initialized));
}
// Type can contain valid uninitialized bits, e.g. padding.
ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(buf.data(), buf.size());
OneWordValue().store(absl::bit_cast<int64_t>(buf),
std::memory_order_release);
break;
}
case FlagValueStorageKind::kSequenceLocked: {
// For this storage kind the default_value_ always points to gen_func
// during initialization.
assert(def_kind == FlagDefaultKind::kGenFunc);
(*default_value_.gen_func)(AtomicBufferValue());
break;
}
case FlagValueStorageKind::kAlignedBuffer:
// For this storage kind the default_value_ always points to gen_func
// during initialization.
assert(def_kind == FlagDefaultKind::kGenFunc);
(*default_value_.gen_func)(AlignedBufferValue());
break;
}
seq_lock_.MarkInitialized();
}
absl::Mutex* FlagImpl::DataGuard() const {
absl::call_once(const_cast<FlagImpl*>(this)->init_control_, &FlagImpl::Init,
const_cast<FlagImpl*>(this));
// data_guard_ is initialized inside Init.
return reinterpret_cast<absl::Mutex*>(&data_guard_);
}
void FlagImpl::AssertValidType(FlagFastTypeId rhs_type_id,
const std::type_info* (*gen_rtti)()) const {
FlagFastTypeId lhs_type_id = flags_internal::FastTypeId(op_);
// `rhs_type_id` is the fast type id corresponding to the declaration
// visible at the call site. `lhs_type_id` is the fast type id
// corresponding to the type specified in flag definition. They must match
// for this operation to be well-defined.
if (ABSL_PREDICT_TRUE(lhs_type_id == rhs_type_id)) return;
const std::type_info* lhs_runtime_type_id =
flags_internal::RuntimeTypeId(op_);
const std::type_info* rhs_runtime_type_id = (*gen_rtti)();
if (lhs_runtime_type_id == rhs_runtime_type_id) return;
#ifdef ABSL_INTERNAL_HAS_RTTI
if (*lhs_runtime_type_id == *rhs_runtime_type_id) return;
#endif
ABSL_INTERNAL_LOG(
FATAL, absl::StrCat("Flag '", Name(),
"' is defined as one type and declared as another"));
}
std::unique_ptr<void, DynValueDeleter> FlagImpl::MakeInitValue() const {
void* res = nullptr;
switch (DefaultKind()) {
case FlagDefaultKind::kDynamicValue:
res = flags_internal::Clone(op_, default_value_.dynamic_value);
break;
case FlagDefaultKind::kGenFunc:
res = flags_internal::Alloc(op_);
(*default_value_.gen_func)(res);
break;
default:
res = flags_internal::Clone(op_, &default_value_);
break;
}
return {res, DynValueDeleter{op_}};
}
void FlagImpl::StoreValue(const void* src) {
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
// Load the current value to avoid setting 'init' bit manually.
int64_t one_word_val = OneWordValue().load(std::memory_order_acquire);
std::memcpy(&one_word_val, src, Sizeof(op_));
OneWordValue().store(one_word_val, std::memory_order_release);
seq_lock_.IncrementModificationCount();
break;
}
case FlagValueStorageKind::kSequenceLocked: {
seq_lock_.Write(AtomicBufferValue(), src, Sizeof(op_));
break;
}
case FlagValueStorageKind::kAlignedBuffer:
Copy(op_, src, AlignedBufferValue());
seq_lock_.IncrementModificationCount();
break;
}
modified_ = true;
InvokeCallback();
}
absl::string_view FlagImpl::Name() const { return name_; }
std::string FlagImpl::Filename() const {
return flags_internal::GetUsageConfig().normalize_filename(filename_);
}
std::string FlagImpl::Help() const {
return HelpSourceKind() == FlagHelpKind::kLiteral ? help_.literal
: help_.gen_func();
}
FlagFastTypeId FlagImpl::TypeId() const {
return flags_internal::FastTypeId(op_);
}
int64_t FlagImpl::ModificationCount() const {
return seq_lock_.ModificationCount();
}
bool FlagImpl::IsSpecifiedOnCommandLine() const {
absl::MutexLock l(DataGuard());
return on_command_line_;
}
std::string FlagImpl::DefaultValue() const {
absl::MutexLock l(DataGuard());
auto obj = MakeInitValue();
return flags_internal::Unparse(op_, obj.get());
}
std::string FlagImpl::CurrentValue() const {
auto* guard = DataGuard(); // Make sure flag initialized
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
const auto one_word_val =
absl::bit_cast<std::array<char, sizeof(int64_t)>>(
OneWordValue().load(std::memory_order_acquire));
return flags_internal::Unparse(op_, one_word_val.data());
}
case FlagValueStorageKind::kSequenceLocked: {
std::unique_ptr<void, DynValueDeleter> cloned(flags_internal::Alloc(op_),
DynValueDeleter{op_});
ReadSequenceLockedData(cloned.get());
return flags_internal::Unparse(op_, cloned.get());
}
case FlagValueStorageKind::kAlignedBuffer: {
absl::MutexLock l(guard);
return flags_internal::Unparse(op_, AlignedBufferValue());
}
}
return "";
}
void FlagImpl::SetCallback(const FlagCallbackFunc mutation_callback) {
absl::MutexLock l(DataGuard());
if (callback_ == nullptr) {
callback_ = new FlagCallback;
}
callback_->func = mutation_callback;
InvokeCallback();
}
void FlagImpl::InvokeCallback() const {
if (!callback_) return;
// Make a copy of the C-style function pointer that we are about to invoke
// before we release the lock guarding it.
FlagCallbackFunc cb = callback_->func;
// If the flag has a mutation callback this function invokes it. While the
// callback is being invoked the primary flag's mutex is unlocked and it is
// re-locked back after call to callback is completed. Callback invocation is
// guarded by flag's secondary mutex instead which prevents concurrent
// callback invocation. Note that it is possible for other thread to grab the
// primary lock and update flag's value at any time during the callback
// invocation. This is by design. Callback can get a value of the flag if
// necessary, but it might be different from the value initiated the callback
// and it also can be different by the time the callback invocation is
// completed. Requires that *primary_lock be held in exclusive mode; it may be
// released and reacquired by the implementation.
MutexRelock relock(*DataGuard());
absl::MutexLock lock(&callback_->guard);
cb();
}
std::unique_ptr<FlagStateInterface> FlagImpl::SaveState() {
absl::MutexLock l(DataGuard());
bool modified = modified_;
bool on_command_line = on_command_line_;
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
return absl::make_unique<FlagState>(
*this, OneWordValue().load(std::memory_order_acquire), modified,
on_command_line, ModificationCount());
}
case FlagValueStorageKind::kSequenceLocked: {
void* cloned = flags_internal::Alloc(op_);
// Read is guaranteed to be successful because we hold the lock.
bool success =
seq_lock_.TryRead(cloned, AtomicBufferValue(), Sizeof(op_));
assert(success);
static_cast<void>(success);
return absl::make_unique<FlagState>(*this, cloned, modified,
on_command_line, ModificationCount());
}
case FlagValueStorageKind::kAlignedBuffer: {
return absl::make_unique<FlagState>(
*this, flags_internal::Clone(op_, AlignedBufferValue()), modified,
on_command_line, ModificationCount());
}
}
return nullptr;
}
bool FlagImpl::RestoreState(const FlagState& flag_state) {
absl::MutexLock l(DataGuard());
if (flag_state.counter_ == ModificationCount()) {
return false;
}
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic:
StoreValue(&flag_state.value_.one_word);
break;
case FlagValueStorageKind::kSequenceLocked:
case FlagValueStorageKind::kAlignedBuffer:
StoreValue(flag_state.value_.heap_allocated);
break;
}
modified_ = flag_state.modified_;
on_command_line_ = flag_state.on_command_line_;
return true;
}
template <typename StorageT>
StorageT* FlagImpl::OffsetValue() const {
char* p = reinterpret_cast<char*>(const_cast<FlagImpl*>(this));
// The offset is deduced via Flag value type specific op_.
ptrdiff_t offset = flags_internal::ValueOffset(op_);
return reinterpret_cast<StorageT*>(p + offset);
}
void* FlagImpl::AlignedBufferValue() const {
assert(ValueStorageKind() == FlagValueStorageKind::kAlignedBuffer);
return OffsetValue<void>();
}
std::atomic<uint64_t>* FlagImpl::AtomicBufferValue() const {
assert(ValueStorageKind() == FlagValueStorageKind::kSequenceLocked);
return OffsetValue<std::atomic<uint64_t>>();
}
std::atomic<int64_t>& FlagImpl::OneWordValue() const {
assert(ValueStorageKind() == FlagValueStorageKind::kOneWordAtomic ||
ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
return OffsetValue<FlagOneWordValue>()->value;
}
// Attempts to parse supplied `value` string using parsing routine in the `flag`
// argument. If parsing successful, this function replaces the dst with newly
// parsed value. In case if any error is encountered in either step, the error
// message is stored in 'err'
std::unique_ptr<void, DynValueDeleter> FlagImpl::TryParse(
absl::string_view value, std::string& err) const {
std::unique_ptr<void, DynValueDeleter> tentative_value = MakeInitValue();
std::string parse_err;
if (!flags_internal::Parse(op_, value, tentative_value.get(), &parse_err)) {
absl::string_view err_sep = parse_err.empty() ? "" : "; ";
err = absl::StrCat("Illegal value '", value, "' specified for flag '",
Name(), "'", err_sep, parse_err);
return nullptr;
}
return tentative_value;
}
void FlagImpl::Read(void* dst) const {
auto* guard = DataGuard(); // Make sure flag initialized
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
const int64_t one_word_val =
OneWordValue().load(std::memory_order_acquire);
std::memcpy(dst, &one_word_val, Sizeof(op_));
break;
}
case FlagValueStorageKind::kSequenceLocked: {
ReadSequenceLockedData(dst);
break;
}
case FlagValueStorageKind::kAlignedBuffer: {
absl::MutexLock l(guard);
flags_internal::CopyConstruct(op_, AlignedBufferValue(), dst);
break;
}
}
}
int64_t FlagImpl::ReadOneWord() const {
assert(ValueStorageKind() == FlagValueStorageKind::kOneWordAtomic ||
ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
auto* guard = DataGuard(); // Make sure flag initialized
(void)guard;
return OneWordValue().load(std::memory_order_acquire);
}
bool FlagImpl::ReadOneBool() const {
assert(ValueStorageKind() == FlagValueStorageKind::kValueAndInitBit);
auto* guard = DataGuard(); // Make sure flag initialized
(void)guard;
return absl::bit_cast<FlagValueAndInitBit<bool>>(
OneWordValue().load(std::memory_order_acquire))
.value;
}
void FlagImpl::ReadSequenceLockedData(void* dst) const {
size_t size = Sizeof(op_);
// Attempt to read using the sequence lock.
if (ABSL_PREDICT_TRUE(seq_lock_.TryRead(dst, AtomicBufferValue(), size))) {
return;
}
// We failed due to contention. Acquire the lock to prevent contention
// and try again.
absl::ReaderMutexLock l(DataGuard());
bool success = seq_lock_.TryRead(dst, AtomicBufferValue(), size);
assert(success);
static_cast<void>(success);
}
void FlagImpl::Write(const void* src) {
absl::MutexLock l(DataGuard());
if (ShouldValidateFlagValue(flags_internal::FastTypeId(op_))) {
std::unique_ptr<void, DynValueDeleter> obj{flags_internal::Clone(op_, src),
DynValueDeleter{op_}};
std::string ignored_error;
std::string src_as_str = flags_internal::Unparse(op_, src);
if (!flags_internal::Parse(op_, src_as_str, obj.get(), &ignored_error)) {
ABSL_INTERNAL_LOG(ERROR, absl::StrCat("Attempt to set flag '", Name(),
"' to invalid value ", src_as_str));
}
}
StoreValue(src);
}
// Sets the value of the flag based on specified string `value`. If the flag
// was successfully set to new value, it returns true. Otherwise, sets `err`
// to indicate the error, leaves the flag unchanged, and returns false. There
// are three ways to set the flag's value:
// * Update the current flag value
// * Update the flag's default value
// * Update the current flag value if it was never set before
// The mode is selected based on 'set_mode' parameter.
bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode,
ValueSource source, std::string& err) {
absl::MutexLock l(DataGuard());
switch (set_mode) {
case SET_FLAGS_VALUE: {
// set or modify the flag's value
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
if (source == kCommandLine) {
on_command_line_ = true;
}
break;
}
case SET_FLAG_IF_DEFAULT: {
// set the flag's value, but only if it hasn't been set by someone else
if (modified_) {
// TODO(rogeeff): review and fix this semantic. Currently we do not fail
// in this case if flag is modified. This is misleading since the flag's
// value is not updated even though we return true.
// *err = absl::StrCat(Name(), " is already set to ",
// CurrentValue(), "\n");
// return false;
return true;
}
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
break;
}
case SET_FLAGS_DEFAULT: {
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
if (DefaultKind() == FlagDefaultKind::kDynamicValue) {
void* old_value = default_value_.dynamic_value;
default_value_.dynamic_value = tentative_value.release();
tentative_value.reset(old_value);
} else {
default_value_.dynamic_value = tentative_value.release();
def_kind_ = static_cast<uint8_t>(FlagDefaultKind::kDynamicValue);
}
if (!modified_) {
// Need to set both default value *and* current, in this case.
StoreValue(default_value_.dynamic_value);
modified_ = false;
}
break;
}
}
return true;
}
void FlagImpl::CheckDefaultValueParsingRoundtrip() const {
std::string v = DefaultValue();
absl::MutexLock lock(DataGuard());
auto dst = MakeInitValue();
std::string error;
if (!flags_internal::Parse(op_, v, dst.get(), &error)) {
ABSL_INTERNAL_LOG(
FATAL,
absl::StrCat("Flag ", Name(), " (from ", Filename(),
"): string form of default value '", v,
"' could not be parsed; error=", error));
}
// We do not compare dst to def since parsing/unparsing may make
// small changes, e.g., precision loss for floating point types.
}
bool FlagImpl::ValidateInputValue(absl::string_view value) const {
absl::MutexLock l(DataGuard());
auto obj = MakeInitValue();
std::string ignored_error;
return flags_internal::Parse(op_, value, obj.get(), &ignored_error);
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl

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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.
#ifndef ABSL_FLAGS_INTERNAL_FLAG_H_
#define ABSL_FLAGS_INTERNAL_FLAG_H_
#include <stddef.h>
#include <stdint.h>
#include <atomic>
#include <cstring>
#include <memory>
#include <new>
#include <string>
#include <type_traits>
#include <typeinfo>
#include "absl/base/attributes.h"
#include "absl/base/call_once.h"
#include "absl/base/casts.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"
#include "absl/base/thread_annotations.h"
#include "absl/flags/commandlineflag.h"
#include "absl/flags/config.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/flags/internal/registry.h"
#include "absl/flags/internal/sequence_lock.h"
#include "absl/flags/marshalling.h"
#include "absl/meta/type_traits.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
#include "absl/utility/utility.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
///////////////////////////////////////////////////////////////////////////////
// Forward declaration of absl::Flag<T> public API.
namespace flags_internal {
template <typename T>
class Flag;
} // namespace flags_internal
template <typename T>
using Flag = flags_internal::Flag<T>;
template <typename T>
ABSL_MUST_USE_RESULT T GetFlag(const absl::Flag<T>& flag);
template <typename T>
void SetFlag(absl::Flag<T>* flag, const T& v);
template <typename T, typename V>
void SetFlag(absl::Flag<T>* flag, const V& v);
template <typename U>
const CommandLineFlag& GetFlagReflectionHandle(const absl::Flag<U>& f);
///////////////////////////////////////////////////////////////////////////////
// Flag value type operations, eg., parsing, copying, etc. are provided
// by function specific to that type with a signature matching FlagOpFn.
namespace flags_internal {
enum class FlagOp {
kAlloc,
kDelete,
kCopy,
kCopyConstruct,
kSizeof,
kFastTypeId,
kRuntimeTypeId,
kParse,
kUnparse,
kValueOffset,
};
using FlagOpFn = void* (*)(FlagOp, const void*, void*, void*);
// Forward declaration for Flag value specific operations.
template <typename T>
void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3);
// Allocate aligned memory for a flag value.
inline void* Alloc(FlagOpFn op) {
return op(FlagOp::kAlloc, nullptr, nullptr, nullptr);
}
// Deletes memory interpreting obj as flag value type pointer.
inline void Delete(FlagOpFn op, void* obj) {
op(FlagOp::kDelete, nullptr, obj, nullptr);
}
// Copies src to dst interpreting as flag value type pointers.
inline void Copy(FlagOpFn op, const void* src, void* dst) {
op(FlagOp::kCopy, src, dst, nullptr);
}
// Construct a copy of flag value in a location pointed by dst
// based on src - pointer to the flag's value.
inline void CopyConstruct(FlagOpFn op, const void* src, void* dst) {
op(FlagOp::kCopyConstruct, src, dst, nullptr);
}
// Makes a copy of flag value pointed by obj.
inline void* Clone(FlagOpFn op, const void* obj) {
void* res = flags_internal::Alloc(op);
flags_internal::CopyConstruct(op, obj, res);
return res;
}
// Returns true if parsing of input text is successful.
inline bool Parse(FlagOpFn op, absl::string_view text, void* dst,
std::string* error) {
return op(FlagOp::kParse, &text, dst, error) != nullptr;
}
// Returns string representing supplied value.
inline std::string Unparse(FlagOpFn op, const void* val) {
std::string result;
op(FlagOp::kUnparse, val, &result, nullptr);
return result;
}
// Returns size of flag value type.
inline size_t Sizeof(FlagOpFn op) {
// This sequence of casts reverses the sequence from
// `flags_internal::FlagOps()`
return static_cast<size_t>(reinterpret_cast<intptr_t>(
op(FlagOp::kSizeof, nullptr, nullptr, nullptr)));
}
// Returns fast type id corresponding to the value type.
inline FlagFastTypeId FastTypeId(FlagOpFn op) {
return reinterpret_cast<FlagFastTypeId>(
op(FlagOp::kFastTypeId, nullptr, nullptr, nullptr));
}
// Returns fast type id corresponding to the value type.
inline const std::type_info* RuntimeTypeId(FlagOpFn op) {
return reinterpret_cast<const std::type_info*>(
op(FlagOp::kRuntimeTypeId, nullptr, nullptr, nullptr));
}
// Returns offset of the field value_ from the field impl_ inside of
// absl::Flag<T> data. Given FlagImpl pointer p you can get the
// location of the corresponding value as:
// reinterpret_cast<char*>(p) + ValueOffset().
inline ptrdiff_t ValueOffset(FlagOpFn op) {
// This sequence of casts reverses the sequence from
// `flags_internal::FlagOps()`
return static_cast<ptrdiff_t>(reinterpret_cast<intptr_t>(
op(FlagOp::kValueOffset, nullptr, nullptr, nullptr)));
}
// Returns an address of RTTI's typeid(T).
template <typename T>
inline const std::type_info* GenRuntimeTypeId() {
#ifdef ABSL_INTERNAL_HAS_RTTI
return &typeid(T);
#else
return nullptr;
#endif
}
///////////////////////////////////////////////////////////////////////////////
// Flag help auxiliary structs.
// This is help argument for absl::Flag encapsulating the string literal pointer
// or pointer to function generating it as well as enum descriminating two
// cases.
using HelpGenFunc = std::string (*)();
template <size_t N>
struct FixedCharArray {
char value[N];
template <size_t... I>
static constexpr FixedCharArray<N> FromLiteralString(
absl::string_view str, absl::index_sequence<I...>) {
return (void)str, FixedCharArray<N>({{str[I]..., '\0'}});
}
};
template <typename Gen, size_t N = Gen::Value().size()>
constexpr FixedCharArray<N + 1> HelpStringAsArray(int) {
return FixedCharArray<N + 1>::FromLiteralString(
Gen::Value(), absl::make_index_sequence<N>{});
}
template <typename Gen>
constexpr std::false_type HelpStringAsArray(char) {
return std::false_type{};
}
union FlagHelpMsg {
constexpr explicit FlagHelpMsg(const char* help_msg) : literal(help_msg) {}
constexpr explicit FlagHelpMsg(HelpGenFunc help_gen) : gen_func(help_gen) {}
const char* literal;
HelpGenFunc gen_func;
};
enum class FlagHelpKind : uint8_t { kLiteral = 0, kGenFunc = 1 };
struct FlagHelpArg {
FlagHelpMsg source;
FlagHelpKind kind;
};
extern const char kStrippedFlagHelp[];
// These two HelpArg overloads allows us to select at compile time one of two
// way to pass Help argument to absl::Flag. We'll be passing
// AbslFlagHelpGenFor##name as Gen and integer 0 as a single argument to prefer
// first overload if possible. If help message is evaluatable on constexpr
// context We'll be able to make FixedCharArray out of it and we'll choose first
// overload. In this case the help message expression is immediately evaluated
// and is used to construct the absl::Flag. No additional code is generated by
// ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the
// consideration, in which case the second overload will be used. The second
// overload does not attempt to evaluate the help message expression
// immediately and instead delays the evaluation by returning the function
// pointer (&T::NonConst) generating the help message when necessary. This is
// evaluatable in constexpr context, but the cost is an extra function being
// generated in the ABSL_FLAG code.
template <typename Gen, size_t N>
constexpr FlagHelpArg HelpArg(const FixedCharArray<N>& value) {
return {FlagHelpMsg(value.value), FlagHelpKind::kLiteral};
}
template <typename Gen>
constexpr FlagHelpArg HelpArg(std::false_type) {
return {FlagHelpMsg(&Gen::NonConst), FlagHelpKind::kGenFunc};
}
///////////////////////////////////////////////////////////////////////////////
// Flag default value auxiliary structs.
// Signature for the function generating the initial flag value (usually
// based on default value supplied in flag's definition)
using FlagDfltGenFunc = void (*)(void*);
union FlagDefaultSrc {
constexpr explicit FlagDefaultSrc(FlagDfltGenFunc gen_func_arg)
: gen_func(gen_func_arg) {}
#define ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE(T, name) \
T name##_value; \
constexpr explicit FlagDefaultSrc(T value) : name##_value(value) {} // NOLINT
ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE)
#undef ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE
void* dynamic_value;
FlagDfltGenFunc gen_func;
};
enum class FlagDefaultKind : uint8_t {
kDynamicValue = 0,
kGenFunc = 1,
kOneWord = 2 // for default values UP to one word in size
};
struct FlagDefaultArg {
FlagDefaultSrc source;
FlagDefaultKind kind;
};
// This struct and corresponding overload to InitDefaultValue are used to
// facilitate usage of {} as default value in ABSL_FLAG macro.
// TODO(rogeeff): Fix handling types with explicit constructors.
struct EmptyBraces {};
template <typename T>
constexpr T InitDefaultValue(T t) {
return t;
}
template <typename T>
constexpr T InitDefaultValue(EmptyBraces) {
return T{};
}
template <typename ValueT, typename GenT,
typename std::enable_if<std::is_integral<ValueT>::value, int>::type =
((void)GenT{}, 0)>
constexpr FlagDefaultArg DefaultArg(int) {
return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kOneWord};
}
template <typename ValueT, typename GenT>
constexpr FlagDefaultArg DefaultArg(char) {
return {FlagDefaultSrc(&GenT::Gen), FlagDefaultKind::kGenFunc};
}
///////////////////////////////////////////////////////////////////////////////
// Flag current value auxiliary structs.
constexpr int64_t UninitializedFlagValue() {
return static_cast<int64_t>(0xababababababababll);
}
template <typename T>
using FlagUseValueAndInitBitStorage =
std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
std::is_default_constructible<T>::value &&
(sizeof(T) < 8)>;
template <typename T>
using FlagUseOneWordStorage =
std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
(sizeof(T) <= 8)>;
template <class T>
using FlagUseSequenceLockStorage =
std::integral_constant<bool, std::is_trivially_copyable<T>::value &&
(sizeof(T) > 8)>;
enum class FlagValueStorageKind : uint8_t {
kValueAndInitBit = 0,
kOneWordAtomic = 1,
kSequenceLocked = 2,
kAlignedBuffer = 3,
};
template <typename T>
static constexpr FlagValueStorageKind StorageKind() {
return FlagUseValueAndInitBitStorage<T>::value
? FlagValueStorageKind::kValueAndInitBit
: FlagUseOneWordStorage<T>::value
? FlagValueStorageKind::kOneWordAtomic
: FlagUseSequenceLockStorage<T>::value
? FlagValueStorageKind::kSequenceLocked
: FlagValueStorageKind::kAlignedBuffer;
}
struct FlagOneWordValue {
constexpr explicit FlagOneWordValue(int64_t v) : value(v) {}
std::atomic<int64_t> value;
};
template <typename T>
struct alignas(8) FlagValueAndInitBit {
T value;
// Use an int instead of a bool to guarantee that a non-zero value has
// a bit set.
uint8_t init;
};
template <typename T,
FlagValueStorageKind Kind = flags_internal::StorageKind<T>()>
struct FlagValue;
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kValueAndInitBit> : FlagOneWordValue {
constexpr FlagValue() : FlagOneWordValue(0) {}
bool Get(const SequenceLock&, T& dst) const {
int64_t storage = value.load(std::memory_order_acquire);
if (ABSL_PREDICT_FALSE(storage == 0)) {
return false;
}
dst = absl::bit_cast<FlagValueAndInitBit<T>>(storage).value;
return true;
}
};
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kOneWordAtomic> : FlagOneWordValue {
constexpr FlagValue() : FlagOneWordValue(UninitializedFlagValue()) {}
bool Get(const SequenceLock&, T& dst) const {
int64_t one_word_val = value.load(std::memory_order_acquire);
if (ABSL_PREDICT_FALSE(one_word_val == UninitializedFlagValue())) {
return false;
}
std::memcpy(&dst, static_cast<const void*>(&one_word_val), sizeof(T));
return true;
}
};
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kSequenceLocked> {
bool Get(const SequenceLock& lock, T& dst) const {
return lock.TryRead(&dst, value_words, sizeof(T));
}
static constexpr int kNumWords =
flags_internal::AlignUp(sizeof(T), sizeof(uint64_t)) / sizeof(uint64_t);
alignas(T) alignas(
std::atomic<uint64_t>) std::atomic<uint64_t> value_words[kNumWords];
};
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kAlignedBuffer> {
bool Get(const SequenceLock&, T&) const { return false; }
alignas(T) char value[sizeof(T)];
};
///////////////////////////////////////////////////////////////////////////////
// Flag callback auxiliary structs.
// Signature for the mutation callback used by watched Flags
// The callback is noexcept.
// TODO(rogeeff): add noexcept after C++17 support is added.
using FlagCallbackFunc = void (*)();
struct FlagCallback {
FlagCallbackFunc func;
absl::Mutex guard; // Guard for concurrent callback invocations.
};
///////////////////////////////////////////////////////////////////////////////
// Flag implementation, which does not depend on flag value type.
// The class encapsulates the Flag's data and access to it.
struct DynValueDeleter {
explicit DynValueDeleter(FlagOpFn op_arg = nullptr);
void operator()(void* ptr) const;
FlagOpFn op;
};
class FlagState;
class FlagImpl final : public CommandLineFlag {
public:
constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
FlagHelpArg help, FlagValueStorageKind value_kind,
FlagDefaultArg default_arg)
: name_(name),
filename_(filename),
op_(op),
help_(help.source),
help_source_kind_(static_cast<uint8_t>(help.kind)),
value_storage_kind_(static_cast<uint8_t>(value_kind)),
def_kind_(static_cast<uint8_t>(default_arg.kind)),
modified_(false),
on_command_line_(false),
callback_(nullptr),
default_value_(default_arg.source),
data_guard_{} {}
// Constant access methods
int64_t ReadOneWord() const ABSL_LOCKS_EXCLUDED(*DataGuard());
bool ReadOneBool() const ABSL_LOCKS_EXCLUDED(*DataGuard());
void Read(void* dst) const override ABSL_LOCKS_EXCLUDED(*DataGuard());
void Read(bool* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
*value = ReadOneBool();
}
template <typename T,
absl::enable_if_t<flags_internal::StorageKind<T>() ==
FlagValueStorageKind::kOneWordAtomic,
int> = 0>
void Read(T* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
int64_t v = ReadOneWord();
std::memcpy(value, static_cast<const void*>(&v), sizeof(T));
}
template <typename T,
typename std::enable_if<flags_internal::StorageKind<T>() ==
FlagValueStorageKind::kValueAndInitBit,
int>::type = 0>
void Read(T* value) const ABSL_LOCKS_EXCLUDED(*DataGuard()) {
*value = absl::bit_cast<FlagValueAndInitBit<T>>(ReadOneWord()).value;
}
// Mutating access methods
void Write(const void* src) ABSL_LOCKS_EXCLUDED(*DataGuard());
// Interfaces to operate on callbacks.
void SetCallback(const FlagCallbackFunc mutation_callback)
ABSL_LOCKS_EXCLUDED(*DataGuard());
void InvokeCallback() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Used in read/write operations to validate source/target has correct type.
// For example if flag is declared as absl::Flag<int> FLAGS_foo, a call to
// absl::GetFlag(FLAGS_foo) validates that the type of FLAGS_foo is indeed
// int. To do that we pass the "assumed" type id (which is deduced from type
// int) as an argument `type_id`, which is in turn is validated against the
// type id stored in flag object by flag definition statement.
void AssertValidType(FlagFastTypeId type_id,
const std::type_info* (*gen_rtti)()) const;
private:
template <typename T>
friend class Flag;
friend class FlagState;
// Ensures that `data_guard_` is initialized and returns it.
absl::Mutex* DataGuard() const
ABSL_LOCK_RETURNED(reinterpret_cast<absl::Mutex*>(data_guard_));
// Returns heap allocated value of type T initialized with default value.
std::unique_ptr<void, DynValueDeleter> MakeInitValue() const
ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Flag initialization called via absl::call_once.
void Init();
// Offset value access methods. One per storage kind. These methods to not
// respect const correctness, so be very carefull using them.
// This is a shared helper routine which encapsulates most of the magic. Since
// it is only used inside the three routines below, which are defined in
// flag.cc, we can define it in that file as well.
template <typename StorageT>
StorageT* OffsetValue() const;
// This is an accessor for a value stored in an aligned buffer storage
// used for non-trivially-copyable data types.
// Returns a mutable pointer to the start of a buffer.
void* AlignedBufferValue() const;
// The same as above, but used for sequencelock-protected storage.
std::atomic<uint64_t>* AtomicBufferValue() const;
// This is an accessor for a value stored as one word atomic. Returns a
// mutable reference to an atomic value.
std::atomic<int64_t>& OneWordValue() const;
// Attempts to parse supplied `value` string. If parsing is successful,
// returns new value. Otherwise returns nullptr.
std::unique_ptr<void, DynValueDeleter> TryParse(absl::string_view value,
std::string& err) const
ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Stores the flag value based on the pointer to the source.
void StoreValue(const void* src) ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Copy the flag data, protected by `seq_lock_` into `dst`.
//
// REQUIRES: ValueStorageKind() == kSequenceLocked.
void ReadSequenceLockedData(void* dst) const
ABSL_LOCKS_EXCLUDED(*DataGuard());
FlagHelpKind HelpSourceKind() const {
return static_cast<FlagHelpKind>(help_source_kind_);
}
FlagValueStorageKind ValueStorageKind() const {
return static_cast<FlagValueStorageKind>(value_storage_kind_);
}
FlagDefaultKind DefaultKind() const
ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()) {
return static_cast<FlagDefaultKind>(def_kind_);
}
// CommandLineFlag interface implementation
absl::string_view Name() const override;
std::string Filename() const override;
std::string Help() const override;
FlagFastTypeId TypeId() const override;
bool IsSpecifiedOnCommandLine() const override
ABSL_LOCKS_EXCLUDED(*DataGuard());
std::string DefaultValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
std::string CurrentValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard());
bool ValidateInputValue(absl::string_view value) const override
ABSL_LOCKS_EXCLUDED(*DataGuard());
void CheckDefaultValueParsingRoundtrip() const override
ABSL_LOCKS_EXCLUDED(*DataGuard());
int64_t ModificationCount() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Interfaces to save and restore flags to/from persistent state.
// Returns current flag state or nullptr if flag does not support
// saving and restoring a state.
std::unique_ptr<FlagStateInterface> SaveState() override
ABSL_LOCKS_EXCLUDED(*DataGuard());
// Restores the flag state to the supplied state object. If there is
// nothing to restore returns false. Otherwise returns true.
bool RestoreState(const FlagState& flag_state)
ABSL_LOCKS_EXCLUDED(*DataGuard());
bool ParseFrom(absl::string_view value, FlagSettingMode set_mode,
ValueSource source, std::string& error) override
ABSL_LOCKS_EXCLUDED(*DataGuard());
// Immutable flag's state.
// Flags name passed to ABSL_FLAG as second arg.
const char* const name_;
// The file name where ABSL_FLAG resides.
const char* const filename_;
// Type-specific operations "vtable".
const FlagOpFn op_;
// Help message literal or function to generate it.
const FlagHelpMsg help_;
// Indicates if help message was supplied as literal or generator func.
const uint8_t help_source_kind_ : 1;
// Kind of storage this flag is using for the flag's value.
const uint8_t value_storage_kind_ : 2;
uint8_t : 0; // The bytes containing the const bitfields must not be
// shared with bytes containing the mutable bitfields.
// Mutable flag's state (guarded by `data_guard_`).
// def_kind_ is not guard by DataGuard() since it is accessed in Init without
// locks.
uint8_t def_kind_ : 2;
// Has this flag's value been modified?
bool modified_ : 1 ABSL_GUARDED_BY(*DataGuard());
// Has this flag been specified on command line.
bool on_command_line_ : 1 ABSL_GUARDED_BY(*DataGuard());
// Unique tag for absl::call_once call to initialize this flag.
absl::once_flag init_control_;
// Sequence lock / mutation counter.
flags_internal::SequenceLock seq_lock_;
// Optional flag's callback and absl::Mutex to guard the invocations.
FlagCallback* callback_ ABSL_GUARDED_BY(*DataGuard());
// Either a pointer to the function generating the default value based on the
// value specified in ABSL_FLAG or pointer to the dynamically set default
// value via SetCommandLineOptionWithMode. def_kind_ is used to distinguish
// these two cases.
FlagDefaultSrc default_value_;
// This is reserved space for an absl::Mutex to guard flag data. It will be
// initialized in FlagImpl::Init via placement new.
// We can't use "absl::Mutex data_guard_", since this class is not literal.
// We do not want to use "absl::Mutex* data_guard_", since this would require
// heap allocation during initialization, which is both slows program startup
// and can fail. Using reserved space + placement new allows us to avoid both
// problems.
alignas(absl::Mutex) mutable char data_guard_[sizeof(absl::Mutex)];
};
///////////////////////////////////////////////////////////////////////////////
// The Flag object parameterized by the flag's value type. This class implements
// flag reflection handle interface.
template <typename T>
class Flag {
public:
constexpr Flag(const char* name, const char* filename, FlagHelpArg help,
const FlagDefaultArg default_arg)
: impl_(name, filename, &FlagOps<T>, help,
flags_internal::StorageKind<T>(), default_arg),
value_() {}
// CommandLineFlag interface
absl::string_view Name() const { return impl_.Name(); }
std::string Filename() const { return impl_.Filename(); }
std::string Help() const { return impl_.Help(); }
// Do not use. To be removed.
bool IsSpecifiedOnCommandLine() const {
return impl_.IsSpecifiedOnCommandLine();
}
std::string DefaultValue() const { return impl_.DefaultValue(); }
std::string CurrentValue() const { return impl_.CurrentValue(); }
private:
template <typename, bool>
friend class FlagRegistrar;
friend class FlagImplPeer;
T Get() const {
// See implementation notes in CommandLineFlag::Get().
union U {
T value;
U() {}
~U() { value.~T(); }
};
U u;
#if !defined(NDEBUG)
impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>);
#endif
if (ABSL_PREDICT_FALSE(!value_.Get(impl_.seq_lock_, u.value))) {
impl_.Read(&u.value);
}
return std::move(u.value);
}
void Set(const T& v) {
impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>);
impl_.Write(&v);
}
// Access to the reflection.
const CommandLineFlag& Reflect() const { return impl_; }
// Flag's data
// The implementation depends on value_ field to be placed exactly after the
// impl_ field, so that impl_ can figure out the offset to the value and
// access it.
FlagImpl impl_;
FlagValue<T> value_;
};
///////////////////////////////////////////////////////////////////////////////
// Trampoline for friend access
class FlagImplPeer {
public:
template <typename T, typename FlagType>
static T InvokeGet(const FlagType& flag) {
return flag.Get();
}
template <typename FlagType, typename T>
static void InvokeSet(FlagType& flag, const T& v) {
flag.Set(v);
}
template <typename FlagType>
static const CommandLineFlag& InvokeReflect(const FlagType& f) {
return f.Reflect();
}
};
///////////////////////////////////////////////////////////////////////////////
// Implementation of Flag value specific operations routine.
template <typename T>
void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3) {
switch (op) {
case FlagOp::kAlloc: {
std::allocator<T> alloc;
return std::allocator_traits<std::allocator<T>>::allocate(alloc, 1);
}
case FlagOp::kDelete: {
T* p = static_cast<T*>(v2);
p->~T();
std::allocator<T> alloc;
std::allocator_traits<std::allocator<T>>::deallocate(alloc, p, 1);
return nullptr;
}
case FlagOp::kCopy:
*static_cast<T*>(v2) = *static_cast<const T*>(v1);
return nullptr;
case FlagOp::kCopyConstruct:
new (v2) T(*static_cast<const T*>(v1));
return nullptr;
case FlagOp::kSizeof:
return reinterpret_cast<void*>(static_cast<uintptr_t>(sizeof(T)));
case FlagOp::kFastTypeId:
return const_cast<void*>(base_internal::FastTypeId<T>());
case FlagOp::kRuntimeTypeId:
return const_cast<std::type_info*>(GenRuntimeTypeId<T>());
case FlagOp::kParse: {
// Initialize the temporary instance of type T based on current value in
// destination (which is going to be flag's default value).
T temp(*static_cast<T*>(v2));
if (!absl::ParseFlag<T>(*static_cast<const absl::string_view*>(v1), &temp,
static_cast<std::string*>(v3))) {
return nullptr;
}
*static_cast<T*>(v2) = std::move(temp);
return v2;
}
case FlagOp::kUnparse:
*static_cast<std::string*>(v2) =
absl::UnparseFlag<T>(*static_cast<const T*>(v1));
return nullptr;
case FlagOp::kValueOffset: {
// Round sizeof(FlagImp) to a multiple of alignof(FlagValue<T>) to get the
// offset of the data.
size_t round_to = alignof(FlagValue<T>);
size_t offset =
(sizeof(FlagImpl) + round_to - 1) / round_to * round_to;
return reinterpret_cast<void*>(offset);
}
}
return nullptr;
}
///////////////////////////////////////////////////////////////////////////////
// This class facilitates Flag object registration and tail expression-based
// flag definition, for example:
// ABSL_FLAG(int, foo, 42, "Foo help").OnUpdate(NotifyFooWatcher);
struct FlagRegistrarEmpty {};
template <typename T, bool do_register>
class FlagRegistrar {
public:
explicit FlagRegistrar(Flag<T>& flag, const char* filename) : flag_(flag) {
if (do_register)
flags_internal::RegisterCommandLineFlag(flag_.impl_, filename);
}
FlagRegistrar OnUpdate(FlagCallbackFunc cb) && {
flag_.impl_.SetCallback(cb);
return *this;
}
// Make the registrar "die" gracefully as an empty struct on a line where
// registration happens. Registrar objects are intended to live only as
// temporary.
operator FlagRegistrarEmpty() const { return {}; } // NOLINT
private:
Flag<T>& flag_; // Flag being registered (not owned).
};
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_FLAG_H_

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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.
#ifndef ABSL_FLAGS_INTERNAL_PATH_UTIL_H_
#define ABSL_FLAGS_INTERNAL_PATH_UTIL_H_
#include "absl/base/config.h"
#include "absl/strings/string_view.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// A portable interface that returns the basename of the filename passed as an
// argument. It is similar to basename(3)
// <https://linux.die.net/man/3/basename>.
// For example:
// flags_internal::Basename("a/b/prog/file.cc")
// returns "file.cc"
// flags_internal::Basename("file.cc")
// returns "file.cc"
inline absl::string_view Basename(absl::string_view filename) {
auto last_slash_pos = filename.find_last_of("/\\");
return last_slash_pos == absl::string_view::npos
? filename
: filename.substr(last_slash_pos + 1);
}
// A portable interface that returns the directory name of the filename
// passed as an argument, including the trailing slash.
// Returns the empty string if a slash is not found in the input file name.
// For example:
// flags_internal::Package("a/b/prog/file.cc")
// returns "a/b/prog/"
// flags_internal::Package("file.cc")
// returns ""
inline absl::string_view Package(absl::string_view filename) {
auto last_slash_pos = filename.find_last_of("/\\");
return last_slash_pos == absl::string_view::npos
? absl::string_view()
: filename.substr(0, last_slash_pos + 1);
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_PATH_UTIL_H_

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//
// Copyright 2020 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/internal/private_handle_accessor.h"
#include <memory>
#include <string>
#include "absl/base/config.h"
#include "absl/flags/commandlineflag.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/strings/string_view.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
FlagFastTypeId PrivateHandleAccessor::TypeId(const CommandLineFlag& flag) {
return flag.TypeId();
}
std::unique_ptr<FlagStateInterface> PrivateHandleAccessor::SaveState(
CommandLineFlag& flag) {
return flag.SaveState();
}
bool PrivateHandleAccessor::IsSpecifiedOnCommandLine(
const CommandLineFlag& flag) {
return flag.IsSpecifiedOnCommandLine();
}
bool PrivateHandleAccessor::ValidateInputValue(const CommandLineFlag& flag,
absl::string_view value) {
return flag.ValidateInputValue(value);
}
void PrivateHandleAccessor::CheckDefaultValueParsingRoundtrip(
const CommandLineFlag& flag) {
flag.CheckDefaultValueParsingRoundtrip();
}
bool PrivateHandleAccessor::ParseFrom(CommandLineFlag& flag,
absl::string_view value,
flags_internal::FlagSettingMode set_mode,
flags_internal::ValueSource source,
std::string& error) {
return flag.ParseFrom(value, set_mode, source, error);
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl

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//
// Copyright 2020 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.
#ifndef ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
#define ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
#include <memory>
#include <string>
#include "absl/base/config.h"
#include "absl/flags/commandlineflag.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/strings/string_view.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// This class serves as a trampoline to access private methods of
// CommandLineFlag. This class is intended for use exclusively internally inside
// of the Abseil Flags implementation.
class PrivateHandleAccessor {
public:
// Access to CommandLineFlag::TypeId.
static FlagFastTypeId TypeId(const CommandLineFlag& flag);
// Access to CommandLineFlag::SaveState.
static std::unique_ptr<FlagStateInterface> SaveState(CommandLineFlag& flag);
// Access to CommandLineFlag::IsSpecifiedOnCommandLine.
static bool IsSpecifiedOnCommandLine(const CommandLineFlag& flag);
// Access to CommandLineFlag::ValidateInputValue.
static bool ValidateInputValue(const CommandLineFlag& flag,
absl::string_view value);
// Access to CommandLineFlag::CheckDefaultValueParsingRoundtrip.
static void CheckDefaultValueParsingRoundtrip(const CommandLineFlag& flag);
static bool ParseFrom(CommandLineFlag& flag, absl::string_view value,
flags_internal::FlagSettingMode set_mode,
flags_internal::ValueSource source, std::string& error);
};
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_

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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/internal/program_name.h"
#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/strings/string_view.h"
#include "absl/synchronization/mutex.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
ABSL_CONST_INIT static absl::Mutex program_name_guard(absl::kConstInit);
ABSL_CONST_INIT static std::string* program_name
ABSL_GUARDED_BY(program_name_guard) = nullptr;
std::string ProgramInvocationName() {
absl::MutexLock l(&program_name_guard);
return program_name ? *program_name : "UNKNOWN";
}
std::string ShortProgramInvocationName() {
absl::MutexLock l(&program_name_guard);
return program_name ? std::string(flags_internal::Basename(*program_name))
: "UNKNOWN";
}
void SetProgramInvocationName(absl::string_view prog_name_str) {
absl::MutexLock l(&program_name_guard);
if (!program_name)
program_name = new std::string(prog_name_str);
else
program_name->assign(prog_name_str.data(), prog_name_str.size());
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl

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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.
#ifndef ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_
#define ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_
#include <string>
#include "absl/base/config.h"
#include "absl/strings/string_view.h"
// --------------------------------------------------------------------
// Program name
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// Returns program invocation name or "UNKNOWN" if `SetProgramInvocationName()`
// is never called. At the moment this is always set to argv[0] as part of
// library initialization.
std::string ProgramInvocationName();
// Returns base name for program invocation name. For example, if
// ProgramInvocationName() == "a/b/mybinary"
// then
// ShortProgramInvocationName() == "mybinary"
std::string ShortProgramInvocationName();
// Sets program invocation name to a new value. Should only be called once
// during program initialization, before any threads are spawned.
void SetProgramInvocationName(absl::string_view prog_name_str);
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_

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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.
#ifndef ABSL_FLAGS_INTERNAL_REGISTRY_H_
#define ABSL_FLAGS_INTERNAL_REGISTRY_H_
#include <functional>
#include "absl/base/config.h"
#include "absl/flags/commandlineflag.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/strings/string_view.h"
// --------------------------------------------------------------------
// Global flags registry API.
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// Executes specified visitor for each non-retired flag in the registry. While
// callback are executed, the registry is locked and can't be changed.
void ForEachFlag(std::function<void(CommandLineFlag&)> visitor);
//-----------------------------------------------------------------------------
bool RegisterCommandLineFlag(CommandLineFlag&, const char* filename);
void FinalizeRegistry();
//-----------------------------------------------------------------------------
// Retired registrations:
//
// Retired flag registrations are treated specially. A 'retired' flag is
// provided only for compatibility with automated invocations that still
// name it. A 'retired' flag:
// - is not bound to a C++ FLAGS_ reference.
// - has a type and a value, but that value is intentionally inaccessible.
// - does not appear in --help messages.
// - is fully supported by _all_ flag parsing routines.
// - consumes args normally, and complains about type mismatches in its
// argument.
// - emits a complaint but does not die (e.g. LOG(ERROR)) if it is
// accessed by name through the flags API for parsing or otherwise.
//
// The registrations for a flag happen in an unspecified order as the
// initializers for the namespace-scope objects of a program are run.
// Any number of weak registrations for a flag can weakly define the flag.
// One non-weak registration will upgrade the flag from weak to non-weak.
// Further weak registrations of a non-weak flag are ignored.
//
// This mechanism is designed to support moving dead flags into a
// 'graveyard' library. An example migration:
//
// 0: Remove references to this FLAGS_flagname in the C++ codebase.
// 1: Register as 'retired' in old_lib.
// 2: Make old_lib depend on graveyard.
// 3: Add a redundant 'retired' registration to graveyard.
// 4: Remove the old_lib 'retired' registration.
// 5: Eventually delete the graveyard registration entirely.
//
// Retire flag with name "name" and type indicated by ops.
void Retire(const char* name, FlagFastTypeId type_id, char* buf);
constexpr size_t kRetiredFlagObjSize = 3 * sizeof(void*);
constexpr size_t kRetiredFlagObjAlignment = alignof(void*);
// Registered a retired flag with name 'flag_name' and type 'T'.
template <typename T>
class RetiredFlag {
public:
void Retire(const char* flag_name) {
flags_internal::Retire(flag_name, base_internal::FastTypeId<T>(), buf_);
}
private:
alignas(kRetiredFlagObjAlignment) char buf_[kRetiredFlagObjSize];
};
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_REGISTRY_H_

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//
// Copyright 2020 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.
#ifndef ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_
#define ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_
#include <stddef.h>
#include <stdint.h>
#include <atomic>
#include <cassert>
#include <cstring>
#include "absl/base/optimization.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// Align 'x' up to the nearest 'align' bytes.
inline constexpr size_t AlignUp(size_t x, size_t align) {
return align * ((x + align - 1) / align);
}
// A SequenceLock implements lock-free reads. A sequence counter is incremented
// before and after each write, and readers access the counter before and after
// accessing the protected data. If the counter is verified to not change during
// the access, and the sequence counter value was even, then the reader knows
// that the read was race-free and valid. Otherwise, the reader must fall back
// to a Mutex-based code path.
//
// This particular SequenceLock starts in an "uninitialized" state in which
// TryRead() returns false. It must be enabled by calling MarkInitialized().
// This serves as a marker that the associated flag value has not yet been
// initialized and a slow path needs to be taken.
//
// The memory reads and writes protected by this lock must use the provided
// `TryRead()` and `Write()` functions. These functions behave similarly to
// `memcpy()`, with one oddity: the protected data must be an array of
// `std::atomic<uint64>`. This is to comply with the C++ standard, which
// considers data races on non-atomic objects to be undefined behavior. See "Can
// Seqlocks Get Along With Programming Language Memory Models?"[1] by Hans J.
// Boehm for more details.
//
// [1] https://www.hpl.hp.com/techreports/2012/HPL-2012-68.pdf
class SequenceLock {
public:
constexpr SequenceLock() : lock_(kUninitialized) {}
// Mark that this lock is ready for use.
void MarkInitialized() {
assert(lock_.load(std::memory_order_relaxed) == kUninitialized);
lock_.store(0, std::memory_order_release);
}
// Copy "size" bytes of data from "src" to "dst", protected as a read-side
// critical section of the sequence lock.
//
// Unlike traditional sequence lock implementations which loop until getting a
// clean read, this implementation returns false in the case of concurrent
// calls to `Write`. In such a case, the caller should fall back to a
// locking-based slow path.
//
// Returns false if the sequence lock was not yet marked as initialized.
//
// NOTE: If this returns false, "dst" may be overwritten with undefined
// (potentially uninitialized) data.
bool TryRead(void* dst, const std::atomic<uint64_t>* src, size_t size) const {
// Acquire barrier ensures that no loads done by f() are reordered
// above the first load of the sequence counter.
int64_t seq_before = lock_.load(std::memory_order_acquire);
if (ABSL_PREDICT_FALSE(seq_before & 1) == 1) return false;
RelaxedCopyFromAtomic(dst, src, size);
// Another acquire fence ensures that the load of 'lock_' below is
// strictly ordered after the RelaxedCopyToAtomic call above.
std::atomic_thread_fence(std::memory_order_acquire);
int64_t seq_after = lock_.load(std::memory_order_relaxed);
return ABSL_PREDICT_TRUE(seq_before == seq_after);
}
// Copy "size" bytes from "src" to "dst" as a write-side critical section
// of the sequence lock. Any concurrent readers will be forced to retry
// until they get a read that does not conflict with this write.
//
// This call must be externally synchronized against other calls to Write,
// but may proceed concurrently with reads.
void Write(std::atomic<uint64_t>* dst, const void* src, size_t size) {
// We can use relaxed instructions to increment the counter since we
// are extenally synchronized. The std::atomic_thread_fence below
// ensures that the counter updates don't get interleaved with the
// copy to the data.
int64_t orig_seq = lock_.load(std::memory_order_relaxed);
assert((orig_seq & 1) == 0); // Must be initially unlocked.
lock_.store(orig_seq + 1, std::memory_order_relaxed);
// We put a release fence between update to lock_ and writes to shared data.
// Thus all stores to shared data are effectively release operations and
// update to lock_ above cannot be re-ordered past any of them. Note that
// this barrier is not for the fetch_add above. A release barrier for the
// fetch_add would be before it, not after.
std::atomic_thread_fence(std::memory_order_release);
RelaxedCopyToAtomic(dst, src, size);
// "Release" semantics ensure that none of the writes done by
// RelaxedCopyToAtomic() can be reordered after the following modification.
lock_.store(orig_seq + 2, std::memory_order_release);
}
// Return the number of times that Write() has been called.
//
// REQUIRES: This must be externally synchronized against concurrent calls to
// `Write()` or `IncrementModificationCount()`.
// REQUIRES: `MarkInitialized()` must have been previously called.
int64_t ModificationCount() const {
int64_t val = lock_.load(std::memory_order_relaxed);
assert(val != kUninitialized && (val & 1) == 0);
return val / 2;
}
// REQUIRES: This must be externally synchronized against concurrent calls to
// `Write()` or `ModificationCount()`.
// REQUIRES: `MarkInitialized()` must have been previously called.
void IncrementModificationCount() {
int64_t val = lock_.load(std::memory_order_relaxed);
assert(val != kUninitialized);
lock_.store(val + 2, std::memory_order_relaxed);
}
private:
// Perform the equivalent of "memcpy(dst, src, size)", but using relaxed
// atomics.
static void RelaxedCopyFromAtomic(void* dst, const std::atomic<uint64_t>* src,
size_t size) {
char* dst_byte = static_cast<char*>(dst);
while (size >= sizeof(uint64_t)) {
uint64_t word = src->load(std::memory_order_relaxed);
std::memcpy(dst_byte, &word, sizeof(word));
dst_byte += sizeof(word);
src++;
size -= sizeof(word);
}
if (size > 0) {
uint64_t word = src->load(std::memory_order_relaxed);
std::memcpy(dst_byte, &word, size);
}
}
// Perform the equivalent of "memcpy(dst, src, size)", but using relaxed
// atomics.
static void RelaxedCopyToAtomic(std::atomic<uint64_t>* dst, const void* src,
size_t size) {
const char* src_byte = static_cast<const char*>(src);
while (size >= sizeof(uint64_t)) {
uint64_t word;
std::memcpy(&word, src_byte, sizeof(word));
dst->store(word, std::memory_order_relaxed);
src_byte += sizeof(word);
dst++;
size -= sizeof(word);
}
if (size > 0) {
uint64_t word = 0;
std::memcpy(&word, src_byte, size);
dst->store(word, std::memory_order_relaxed);
}
}
static constexpr int64_t kUninitialized = -1;
std::atomic<int64_t> lock_;
};
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_SEQUENCE_LOCK_H_