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This commit is contained in:
QuFY
2025-09-20 17:13:38 +08:00
parent 7787b3ee30
commit 28ff2b0264
5251 changed files with 345029 additions and 285168 deletions
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147
Pods/abseil/absl/flags/internal/flag.cc generated
View File

@@ -22,14 +22,17 @@
#include <array>
#include <atomic>
#include <cstring>
#include <memory>
#include <new>
#include <string>
#include <typeinfo>
#include <vector>
#include "absl/base/attributes.h"
#include "absl/base/call_once.h"
#include "absl/base/casts.h"
#include "absl/base/config.h"
#include "absl/base/const_init.h"
#include "absl/base/dynamic_annotations.h"
#include "absl/base/optimization.h"
#include "absl/flags/config.h"
@@ -44,10 +47,9 @@ 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
// 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 {
@@ -78,8 +80,31 @@ class MutexRelock {
absl::Mutex& mu_;
};
// This is a freelist of leaked flag values and guard for its access.
// When we can't guarantee it is safe to reuse the memory for flag values,
// we move the memory to the freelist where it lives indefinitely, so it can
// still be safely accessed. This also prevents leak checkers from complaining
// about the leaked memory that can no longer be accessed through any pointer.
ABSL_CONST_INIT absl::Mutex s_freelist_guard(absl::kConstInit);
ABSL_CONST_INIT std::vector<void*>* s_freelist = nullptr;
void AddToFreelist(void* p) {
absl::MutexLock l(&s_freelist_guard);
if (!s_freelist) {
s_freelist = new std::vector<void*>;
}
s_freelist->push_back(p);
}
} // namespace
///////////////////////////////////////////////////////////////////////////////
uint64_t NumLeakedFlagValues() {
absl::MutexLock l(&s_freelist_guard);
return s_freelist == nullptr ? 0u : s_freelist->size();
}
///////////////////////////////////////////////////////////////////////////////
// Persistent state of the flag data.
@@ -97,7 +122,7 @@ class FlagState : public flags_internal::FlagStateInterface {
counter_(counter) {}
~FlagState() override {
if (flag_impl_.ValueStorageKind() != FlagValueStorageKind::kAlignedBuffer &&
if (flag_impl_.ValueStorageKind() != FlagValueStorageKind::kHeapAllocated &&
flag_impl_.ValueStorageKind() != FlagValueStorageKind::kSequenceLocked)
return;
flags_internal::Delete(flag_impl_.op_, value_.heap_allocated);
@@ -140,6 +165,33 @@ void DynValueDeleter::operator()(void* ptr) const {
Delete(op, ptr);
}
MaskedPointer::MaskedPointer(ptr_t rhs, bool is_candidate) : ptr_(rhs) {
if (is_candidate) {
ApplyMask(kUnprotectedReadCandidate);
}
}
bool MaskedPointer::IsUnprotectedReadCandidate() const {
return CheckMask(kUnprotectedReadCandidate);
}
bool MaskedPointer::HasBeenRead() const { return CheckMask(kHasBeenRead); }
void MaskedPointer::Set(FlagOpFn op, const void* src, bool is_candidate) {
flags_internal::Copy(op, src, Ptr());
if (is_candidate) {
ApplyMask(kUnprotectedReadCandidate);
}
}
void MaskedPointer::MarkAsRead() { ApplyMask(kHasBeenRead); }
void MaskedPointer::ApplyMask(mask_t mask) {
ptr_ = reinterpret_cast<ptr_t>(reinterpret_cast<mask_t>(ptr_) | mask);
}
bool MaskedPointer::CheckMask(mask_t mask) const {
return (reinterpret_cast<mask_t>(ptr_) & mask) != 0;
}
void FlagImpl::Init() {
new (&data_guard_) absl::Mutex;
@@ -174,11 +226,16 @@ void FlagImpl::Init() {
(*default_value_.gen_func)(AtomicBufferValue());
break;
}
case FlagValueStorageKind::kAlignedBuffer:
case FlagValueStorageKind::kHeapAllocated:
// For this storage kind the default_value_ always points to gen_func
// during initialization.
assert(def_kind == FlagDefaultKind::kGenFunc);
(*default_value_.gen_func)(AlignedBufferValue());
// Flag value initially points to the internal buffer.
MaskedPointer ptr_value = PtrStorage().load(std::memory_order_acquire);
(*default_value_.gen_func)(ptr_value.Ptr());
// Default value is a candidate for an unprotected read.
PtrStorage().store(MaskedPointer(ptr_value.Ptr(), true),
std::memory_order_release);
break;
}
seq_lock_.MarkInitialized();
@@ -234,7 +291,7 @@ std::unique_ptr<void, DynValueDeleter> FlagImpl::MakeInitValue() const {
return {res, DynValueDeleter{op_}};
}
void FlagImpl::StoreValue(const void* src) {
void FlagImpl::StoreValue(const void* src, ValueSource source) {
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic: {
@@ -249,8 +306,27 @@ void FlagImpl::StoreValue(const void* src) {
seq_lock_.Write(AtomicBufferValue(), src, Sizeof(op_));
break;
}
case FlagValueStorageKind::kAlignedBuffer:
Copy(op_, src, AlignedBufferValue());
case FlagValueStorageKind::kHeapAllocated:
MaskedPointer ptr_value = PtrStorage().load(std::memory_order_acquire);
if (ptr_value.IsUnprotectedReadCandidate() && ptr_value.HasBeenRead()) {
// If current value is a candidate for an unprotected read and if it was
// already read at least once, follow up reads (if any) are done without
// mutex protection. We can't guarantee it is safe to reuse this memory
// since it may have been accessed by another thread concurrently, so
// instead we move the memory to a freelist so it can still be safely
// accessed, and allocate a new one for the new value.
AddToFreelist(ptr_value.Ptr());
ptr_value = MaskedPointer(Clone(op_, src), source == kCommandLine);
} else {
// Current value either was set programmatically or was never read.
// We can reuse the memory since all accesses to this value (if any)
// were protected by mutex. That said, if a new value comes from command
// line it now becomes a candidate for an unprotected read.
ptr_value.Set(op_, src, source == kCommandLine);
}
PtrStorage().store(ptr_value, std::memory_order_release);
seq_lock_.IncrementModificationCount();
break;
}
@@ -305,9 +381,10 @@ std::string FlagImpl::CurrentValue() const {
ReadSequenceLockedData(cloned.get());
return flags_internal::Unparse(op_, cloned.get());
}
case FlagValueStorageKind::kAlignedBuffer: {
case FlagValueStorageKind::kHeapAllocated: {
absl::MutexLock l(guard);
return flags_internal::Unparse(op_, AlignedBufferValue());
return flags_internal::Unparse(
op_, PtrStorage().load(std::memory_order_acquire).Ptr());
}
}
@@ -370,10 +447,12 @@ std::unique_ptr<FlagStateInterface> FlagImpl::SaveState() {
return absl::make_unique<FlagState>(*this, cloned, modified,
on_command_line, ModificationCount());
}
case FlagValueStorageKind::kAlignedBuffer: {
case FlagValueStorageKind::kHeapAllocated: {
return absl::make_unique<FlagState>(
*this, flags_internal::Clone(op_, AlignedBufferValue()), modified,
on_command_line, ModificationCount());
*this,
flags_internal::Clone(
op_, PtrStorage().load(std::memory_order_acquire).Ptr()),
modified, on_command_line, ModificationCount());
}
}
return nullptr;
@@ -388,11 +467,11 @@ bool FlagImpl::RestoreState(const FlagState& flag_state) {
switch (ValueStorageKind()) {
case FlagValueStorageKind::kValueAndInitBit:
case FlagValueStorageKind::kOneWordAtomic:
StoreValue(&flag_state.value_.one_word);
StoreValue(&flag_state.value_.one_word, kProgrammaticChange);
break;
case FlagValueStorageKind::kSequenceLocked:
case FlagValueStorageKind::kAlignedBuffer:
StoreValue(flag_state.value_.heap_allocated);
case FlagValueStorageKind::kHeapAllocated:
StoreValue(flag_state.value_.heap_allocated, kProgrammaticChange);
break;
}
@@ -411,11 +490,6 @@ StorageT* FlagImpl::OffsetValue() const {
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>>();
@@ -427,6 +501,11 @@ std::atomic<int64_t>& FlagImpl::OneWordValue() const {
return OffsetValue<FlagOneWordValue>()->value;
}
std::atomic<MaskedPointer>& FlagImpl::PtrStorage() const {
assert(ValueStorageKind() == FlagValueStorageKind::kHeapAllocated);
return OffsetValue<FlagMaskedPointerValue>()->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
@@ -460,9 +539,17 @@ void FlagImpl::Read(void* dst) const {
ReadSequenceLockedData(dst);
break;
}
case FlagValueStorageKind::kAlignedBuffer: {
case FlagValueStorageKind::kHeapAllocated: {
absl::MutexLock l(guard);
flags_internal::CopyConstruct(op_, AlignedBufferValue(), dst);
MaskedPointer ptr_value = PtrStorage().load(std::memory_order_acquire);
flags_internal::CopyConstruct(op_, ptr_value.Ptr(), dst);
// For unprotected read candidates, mark that the value as has been read.
if (ptr_value.IsUnprotectedReadCandidate() && !ptr_value.HasBeenRead()) {
ptr_value.MarkAsRead();
PtrStorage().store(ptr_value, std::memory_order_release);
}
break;
}
}
@@ -513,7 +600,7 @@ void FlagImpl::Write(const void* src) {
}
}
StoreValue(src);
StoreValue(src, kProgrammaticChange);
}
// Sets the value of the flag based on specified string `value`. If the flag
@@ -534,7 +621,7 @@ bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode,
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
StoreValue(tentative_value.get(), source);
if (source == kCommandLine) {
on_command_line_ = true;
@@ -555,7 +642,7 @@ bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode,
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
StoreValue(tentative_value.get(), source);
break;
}
case SET_FLAGS_DEFAULT: {
@@ -573,7 +660,7 @@ bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode,
if (!modified_) {
// Need to set both default value *and* current, in this case.
StoreValue(default_value_.dynamic_value);
StoreValue(default_value_.dynamic_value, source);
modified_ = false;
}
break;

222
Pods/abseil/absl/flags/internal/flag.h generated
View File

@@ -22,7 +22,6 @@
#include <atomic>
#include <cstring>
#include <memory>
#include <new>
#include <string>
#include <type_traits>
#include <typeinfo>
@@ -296,11 +295,8 @@ constexpr FlagDefaultArg DefaultArg(char) {
}
///////////////////////////////////////////////////////////////////////////////
// Flag current value auxiliary structs.
constexpr int64_t UninitializedFlagValue() {
return static_cast<int64_t>(0xababababababababll);
}
// Flag storage selector traits. Each trait indicates what kind of storage kind
// to use for the flag value.
template <typename T>
using FlagUseValueAndInitBitStorage =
@@ -322,9 +318,11 @@ enum class FlagValueStorageKind : uint8_t {
kValueAndInitBit = 0,
kOneWordAtomic = 1,
kSequenceLocked = 2,
kAlignedBuffer = 3,
kHeapAllocated = 3,
};
// This constexpr function returns the storage kind for the given flag value
// type.
template <typename T>
static constexpr FlagValueStorageKind StorageKind() {
return FlagUseValueAndInitBitStorage<T>::value
@@ -333,14 +331,24 @@ static constexpr FlagValueStorageKind StorageKind() {
? FlagValueStorageKind::kOneWordAtomic
: FlagUseSequenceLockStorage<T>::value
? FlagValueStorageKind::kSequenceLocked
: FlagValueStorageKind::kAlignedBuffer;
: FlagValueStorageKind::kHeapAllocated;
}
// This is a base class for the storage classes used by kOneWordAtomic and
// kValueAndInitBit storage kinds. It literally just stores the one word value
// as an atomic. By default, it is initialized to a magic value that is unlikely
// a valid value for the flag value type.
struct FlagOneWordValue {
constexpr static int64_t Uninitialized() {
return static_cast<int64_t>(0xababababababababll);
}
constexpr FlagOneWordValue() : value(Uninitialized()) {}
constexpr explicit FlagOneWordValue(int64_t v) : value(v) {}
std::atomic<int64_t> value;
};
// This class represents a memory layout used by kValueAndInitBit storage kind.
template <typename T>
struct alignas(8) FlagValueAndInitBit {
T value;
@@ -349,16 +357,91 @@ struct alignas(8) FlagValueAndInitBit {
uint8_t init;
};
// This class implements an aligned pointer with two options stored via masks
// in unused bits of the pointer value (due to alignment requirement).
// - IsUnprotectedReadCandidate - indicates that the value can be switched to
// unprotected read without a lock.
// - HasBeenRead - indicates that the value has been read at least once.
// - AllowsUnprotectedRead - combination of the two options above and indicates
// that the value can now be read without a lock.
// Further details of these options and their use is covered in the description
// of the FlagValue<T, FlagValueStorageKind::kHeapAllocated> specialization.
class MaskedPointer {
public:
using mask_t = uintptr_t;
using ptr_t = void*;
static constexpr int RequiredAlignment() { return 4; }
constexpr explicit MaskedPointer(ptr_t rhs) : ptr_(rhs) {}
MaskedPointer(ptr_t rhs, bool is_candidate);
void* Ptr() const {
return reinterpret_cast<void*>(reinterpret_cast<mask_t>(ptr_) &
kPtrValueMask);
}
bool AllowsUnprotectedRead() const {
return (reinterpret_cast<mask_t>(ptr_) & kAllowsUnprotectedRead) ==
kAllowsUnprotectedRead;
}
bool IsUnprotectedReadCandidate() const;
bool HasBeenRead() const;
void Set(FlagOpFn op, const void* src, bool is_candidate);
void MarkAsRead();
private:
// Masks
// Indicates that the flag value either default or originated from command
// line.
static constexpr mask_t kUnprotectedReadCandidate = 0x1u;
// Indicates that flag has been read.
static constexpr mask_t kHasBeenRead = 0x2u;
static constexpr mask_t kAllowsUnprotectedRead =
kUnprotectedReadCandidate | kHasBeenRead;
static constexpr mask_t kPtrValueMask = ~kAllowsUnprotectedRead;
void ApplyMask(mask_t mask);
bool CheckMask(mask_t mask) const;
ptr_t ptr_;
};
// This class implements a type erased storage of the heap allocated flag value.
// It is used as a base class for the storage class for kHeapAllocated storage
// kind. The initial_buffer is expected to have an alignment of at least
// MaskedPointer::RequiredAlignment(), so that the bits used by the
// MaskedPointer to store masks are set to 0. This guarantees that value starts
// in an uninitialized state.
struct FlagMaskedPointerValue {
constexpr explicit FlagMaskedPointerValue(MaskedPointer::ptr_t initial_buffer)
: value(MaskedPointer(initial_buffer)) {}
std::atomic<MaskedPointer> value;
};
// This is the forward declaration for the template that represents a storage
// for the flag values. This template is expected to be explicitly specialized
// for each storage kind and it does not have a generic default
// implementation.
template <typename T,
FlagValueStorageKind Kind = flags_internal::StorageKind<T>()>
struct FlagValue;
// This specialization represents the storage of flag values types with the
// kValueAndInitBit storage kind. It is based on the FlagOneWordValue class
// and relies on memory layout in FlagValueAndInitBit<T> to indicate that the
// value has been initialized or not.
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)) {
// This assert is to ensure that the initialization inside FlagImpl::Init
// is able to set init member correctly.
static_assert(offsetof(FlagValueAndInitBit<T>, init) == sizeof(T),
"Unexpected memory layout of FlagValueAndInitBit");
return false;
}
dst = absl::bit_cast<FlagValueAndInitBit<T>>(storage).value;
@@ -366,12 +449,16 @@ struct FlagValue<T, FlagValueStorageKind::kValueAndInitBit> : FlagOneWordValue {
}
};
// This specialization represents the storage of flag values types with the
// kOneWordAtomic storage kind. It is based on the FlagOneWordValue class
// and relies on the magic uninitialized state of default constructed instead of
// FlagOneWordValue to indicate that the value has been initialized or not.
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kOneWordAtomic> : FlagOneWordValue {
constexpr FlagValue() : FlagOneWordValue(UninitializedFlagValue()) {}
constexpr FlagValue() : FlagOneWordValue() {}
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())) {
if (ABSL_PREDICT_FALSE(one_word_val == FlagOneWordValue::Uninitialized())) {
return false;
}
std::memcpy(&dst, static_cast<const void*>(&one_word_val), sizeof(T));
@@ -379,6 +466,12 @@ struct FlagValue<T, FlagValueStorageKind::kOneWordAtomic> : FlagOneWordValue {
}
};
// This specialization represents the storage of flag values types with the
// kSequenceLocked storage kind. This storage is used by trivially copyable
// types with size greater than 8 bytes. This storage relies on uninitialized
// state of the SequenceLock to indicate that the value has been initialized or
// not. This storage also provides lock-free read access to the underlying
// value once it is initialized.
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kSequenceLocked> {
bool Get(const SequenceLock& lock, T& dst) const {
@@ -392,11 +485,62 @@ struct FlagValue<T, FlagValueStorageKind::kSequenceLocked> {
std::atomic<uint64_t>) std::atomic<uint64_t> value_words[kNumWords];
};
// This specialization represents the storage of flag values types with the
// kHeapAllocated storage kind. This is a storage of last resort and is used
// if none of other storage kinds are applicable.
//
// Generally speaking the values with this storage kind can't be accessed
// atomically and thus can't be read without holding a lock. If we would ever
// want to avoid the lock, we'd need to leak the old value every time new flag
// value is being set (since we are in danger of having a race condition
// otherwise).
//
// Instead of doing that, this implementation attempts to cater to some common
// use cases by allowing at most 2 values to be leaked - default value and
// value set from the command line.
//
// This specialization provides an initial buffer for the first flag value. This
// is where the default value is going to be stored. We attempt to reuse this
// buffer if possible, including storing the value set from the command line
// there.
//
// As long as we only read this value, we can access it without a lock (in
// practice we still use the lock for the very first read to be able set
// "has been read" option on this flag).
//
// If flag is specified on the command line we store the parsed value either
// in the internal buffer (if the default value never been read) or we leak the
// default value and allocate the new storage for the parse value. This value is
// also a candidate for an unprotected read. If flag is set programmatically
// after the command line is parsed, the storage for this value is going to be
// leaked. Note that in both scenarios we are not going to have a real leak.
// Instead we'll store the leaked value pointers in the internal freelist to
// avoid triggering the memory leak checker complains.
//
// If the flag is ever set programmatically, it stops being the candidate for an
// unprotected read, and any follow up access to the flag value requires a lock.
// Note that if the value if set programmatically before the command line is
// parsed, we can switch back to enabling unprotected reads for that value.
template <typename T>
struct FlagValue<T, FlagValueStorageKind::kAlignedBuffer> {
bool Get(const SequenceLock&, T&) const { return false; }
struct FlagValue<T, FlagValueStorageKind::kHeapAllocated>
: FlagMaskedPointerValue {
// We const initialize the value with unmasked pointer to the internal buffer,
// making sure it is not a candidate for unprotected read. This way we can
// ensure Init is done before any access to the flag value.
constexpr FlagValue() : FlagMaskedPointerValue(&buffer[0]) {}
alignas(T) char value[sizeof(T)];
bool Get(const SequenceLock&, T& dst) const {
MaskedPointer ptr_value = value.load(std::memory_order_acquire);
if (ABSL_PREDICT_TRUE(ptr_value.AllowsUnprotectedRead())) {
::new (static_cast<void*>(&dst)) T(*static_cast<T*>(ptr_value.Ptr()));
return true;
}
return false;
}
alignas(MaskedPointer::RequiredAlignment()) alignas(
T) char buffer[sizeof(T)]{};
};
///////////////////////////////////////////////////////////////////////////////
@@ -425,6 +569,13 @@ struct DynValueDeleter {
class FlagState;
// These are only used as constexpr global objects.
// They do not use a virtual destructor to simplify their implementation.
// They are not destroyed except at program exit, so leaks do not matter.
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
#endif
class FlagImpl final : public CommandLineFlag {
public:
constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
@@ -477,7 +628,7 @@ class FlagImpl final : public CommandLineFlag {
// 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. 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,
@@ -498,17 +649,13 @@ class FlagImpl final : public CommandLineFlag {
void Init();
// Offset value access methods. One per storage kind. These methods to not
// respect const correctness, so be very carefull using them.
// respect const correctness, so be very careful 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;
@@ -517,13 +664,16 @@ class FlagImpl final : public CommandLineFlag {
// mutable reference to an atomic value.
std::atomic<int64_t>& OneWordValue() const;
std::atomic<MaskedPointer>& PtrStorage() 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());
void StoreValue(const void* src, ValueSource source)
ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard());
// Copy the flag data, protected by `seq_lock_` into `dst`.
//
@@ -579,7 +729,7 @@ class FlagImpl final : public CommandLineFlag {
const char* const name_;
// The file name where ABSL_FLAG resides.
const char* const filename_;
// Type-specific operations "vtable".
// Type-specific operations vtable.
const FlagOpFn op_;
// Help message literal or function to generate it.
const FlagHelpMsg help_;
@@ -624,6 +774,9 @@ class FlagImpl final : public CommandLineFlag {
// problems.
alignas(absl::Mutex) mutable char data_guard_[sizeof(absl::Mutex)];
};
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif
///////////////////////////////////////////////////////////////////////////////
// The Flag object parameterized by the flag's value type. This class implements
@@ -711,16 +864,21 @@ class FlagImplPeer {
// Implementation of Flag value specific operations routine.
template <typename T>
void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3) {
struct AlignedSpace {
alignas(MaskedPointer::RequiredAlignment()) alignas(T) char buf[sizeof(T)];
};
using Allocator = std::allocator<AlignedSpace>;
switch (op) {
case FlagOp::kAlloc: {
std::allocator<T> alloc;
return std::allocator_traits<std::allocator<T>>::allocate(alloc, 1);
Allocator alloc;
return std::allocator_traits<Allocator>::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);
Allocator alloc;
std::allocator_traits<Allocator>::deallocate(
alloc, reinterpret_cast<AlignedSpace*>(p), 1);
return nullptr;
}
case FlagOp::kCopy:
@@ -754,8 +912,7 @@ void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3) {
// 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;
size_t offset = (sizeof(FlagImpl) + round_to - 1) / round_to * round_to;
return reinterpret_cast<void*>(offset);
}
}
@@ -770,7 +927,8 @@ struct FlagRegistrarEmpty {};
template <typename T, bool do_register>
class FlagRegistrar {
public:
explicit FlagRegistrar(Flag<T>& flag, const char* filename) : flag_(flag) {
constexpr explicit FlagRegistrar(Flag<T>& flag, const char* filename)
: flag_(flag) {
if (do_register)
flags_internal::RegisterCommandLineFlag(flag_.impl_, filename);
}
@@ -780,15 +938,19 @@ class FlagRegistrar {
return *this;
}
// Make the registrar "die" gracefully as an empty struct on a line where
// Makes 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
constexpr operator FlagRegistrarEmpty() const { return {}; } // NOLINT
private:
Flag<T>& flag_; // Flag being registered (not owned).
};
///////////////////////////////////////////////////////////////////////////////
// Test only API
uint64_t NumLeakedFlagValues();
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl