diff options
Diffstat (limited to 'absl/flags/internal/flag.cc')
| -rw-r--r-- | absl/flags/internal/flag.cc | 340 |
1 files changed, 263 insertions, 77 deletions
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc index 5a921e28..1502e7f1 100644 --- a/absl/flags/internal/flag.cc +++ b/absl/flags/internal/flag.cc @@ -15,21 +15,26 @@ #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 <vector> +#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/const_init.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" @@ -47,10 +52,10 @@ 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(FlagStaticTypeId flag_type_id) { -#define DONT_VALIDATE(T) \ - if (flag_type_id == &FlagStaticTypeIdGen<T>) return false; - ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(DONT_VALIDATE) +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; @@ -62,55 +67,142 @@ bool ShouldValidateFlagValue(FlagStaticTypeId flag_type_id) { // need to acquire these locks themselves. class MutexRelock { public: - explicit MutexRelock(absl::Mutex* mu) : mu_(mu) { mu_->Unlock(); } - ~MutexRelock() { mu_->Lock(); } + 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_; + 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) + 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) {} + explicit SavedValue(flags_internal::AlignedTwoWords v) : two_words(v) {} + + void* heap_allocated; + int64_t one_word; + flags_internal::AlignedTwoWords two_words; + } 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; - absl::MutexLock lock(reinterpret_cast<absl::Mutex*>(&data_guard_)); + auto def_kind = static_cast<FlagDefaultKind>(def_kind_); - value_.dynamic = MakeInitValue().release(); - StoreAtomic(); + switch (ValueStorageKind()) { + 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; + 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_)); + } + OneWordValue().store(absl::bit_cast<int64_t>(buf), + std::memory_order_release); + break; + } + case FlagValueStorageKind::kTwoWordsAtomic: { + // For this storage kind the default_value_ always points to gen_func + // during initialization. + assert(def_kind == FlagDefaultKind::kGenFunc); + alignas(AlignedTwoWords) std::array<char, sizeof(AlignedTwoWords)> buf{}; + (*default_value_.gen_func)(buf.data()); + auto atomic_value = absl::bit_cast<AlignedTwoWords>(buf); + TwoWordsValue().store(atomic_value, std::memory_order_release); + break; + } + } } -// Ensures that the lazily initialized data is initialized, -// and returns pointer to the mutex guarding flags data. absl::Mutex* FlagImpl::DataGuard() const { absl::call_once(const_cast<FlagImpl*>(this)->init_control_, &FlagImpl::Init, const_cast<FlagImpl*>(this)); - // data_guard_ is initialized. + // data_guard_ is initialized inside Init. return reinterpret_cast<absl::Mutex*>(&data_guard_); } -void FlagImpl::AssertValidType(FlagStaticTypeId type_id) const { - FlagStaticTypeId this_type_id = flags_internal::StaticTypeId(op_); +void FlagImpl::AssertValidType(FlagFastTypeId rhs_type_id, + const std::type_info* (*gen_rtti)()) const { + FlagFastTypeId lhs_type_id = flags_internal::FastTypeId(op_); - // `type_id` is the type id corresponding to the declaration visibile at the - // call site. `this_type_id` is the type id corresponding to the type stored - // during flag definition. They must match for this operation to be - // well-defined. - if (ABSL_PREDICT_TRUE(type_id == this_type_id)) return; + // `rhs_type_id` is the fast type id corresponding to the declaration + // visibile 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; - void* lhs_runtime_type_id = type_id(); - void* rhs_runtime_type_id = this_type_id(); + 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; #if defined(ABSL_FLAGS_INTERNAL_HAS_RTTI) - if (*reinterpret_cast<std::type_info*>(lhs_runtime_type_id) == - *reinterpret_cast<std::type_info*>(rhs_runtime_type_id)) - return; + if (*lhs_runtime_type_id == *rhs_runtime_type_id) return; #endif ABSL_INTERNAL_LOG( @@ -120,17 +212,40 @@ void FlagImpl::AssertValidType(FlagStaticTypeId type_id) const { std::unique_ptr<void, DynValueDeleter> FlagImpl::MakeInitValue() const { void* res = nullptr; - if (DefaultKind() == FlagDefaultKind::kDynamicValue) { - res = flags_internal::Clone(op_, default_value_.dynamic_value); - } else { - res = (*default_value_.gen_func)(); + 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) { - flags_internal::Copy(op_, src, value_.dynamic); - StoreAtomic(); + switch (ValueStorageKind()) { + case FlagValueStorageKind::kAlignedBuffer: + Copy(op_, src, AlignedBufferValue()); + break; + case FlagValueStorageKind::kOneWordAtomic: { + int64_t one_word_val = 0; + std::memcpy(&one_word_val, src, Sizeof(op_)); + OneWordValue().store(one_word_val, std::memory_order_release); + break; + } + case FlagValueStorageKind::kTwoWordsAtomic: { + AlignedTwoWords two_words_val{0, 0}; + std::memcpy(&two_words_val, src, Sizeof(op_)); + TwoWordsValue().store(two_words_val, std::memory_order_release); + break; + } + } + modified_ = true; ++counter_; InvokeCallback(); @@ -147,9 +262,8 @@ std::string FlagImpl::Help() const { : help_.gen_func(); } -bool FlagImpl::IsModified() const { - absl::MutexLock l(DataGuard()); - return modified_; +FlagFastTypeId FlagImpl::TypeId() const { + return flags_internal::FastTypeId(op_); } bool FlagImpl::IsSpecifiedOnCommandLine() const { @@ -165,9 +279,27 @@ std::string FlagImpl::DefaultValue() const { } std::string FlagImpl::CurrentValue() const { - absl::MutexLock l(DataGuard()); + auto* guard = DataGuard(); // Make sure flag initialized + switch (ValueStorageKind()) { + case FlagValueStorageKind::kAlignedBuffer: { + absl::MutexLock l(guard); + return flags_internal::Unparse(op_, AlignedBufferValue()); + } + 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::kTwoWordsAtomic: { + const auto two_words_val = + absl::bit_cast<std::array<char, sizeof(AlignedTwoWords)>>( + TwoWordsValue().load(std::memory_order_acquire)); + return flags_internal::Unparse(op_, two_words_val.data()); + } + } - return flags_internal::Unparse(op_, value_.dynamic); + return ""; } void FlagImpl::SetCallback(const FlagCallbackFunc mutation_callback) { @@ -199,44 +331,98 @@ void FlagImpl::InvokeCallback() const { // 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()); + MutexRelock relock(*DataGuard()); absl::MutexLock lock(&callback_->guard); cb(); } -bool FlagImpl::RestoreState(const void* value, bool modified, - bool on_command_line, int64_t counter) { - { - absl::MutexLock l(DataGuard()); +std::unique_ptr<FlagStateInterface> FlagImpl::SaveState() { + absl::MutexLock l(DataGuard()); - if (counter_ == counter) return false; + bool modified = modified_; + bool on_command_line = on_command_line_; + switch (ValueStorageKind()) { + case FlagValueStorageKind::kAlignedBuffer: { + return absl::make_unique<FlagState>( + *this, flags_internal::Clone(op_, AlignedBufferValue()), modified, + on_command_line, counter_); + } + case FlagValueStorageKind::kOneWordAtomic: { + return absl::make_unique<FlagState>( + *this, OneWordValue().load(std::memory_order_acquire), modified, + on_command_line, counter_); + } + case FlagValueStorageKind::kTwoWordsAtomic: { + return absl::make_unique<FlagState>( + *this, TwoWordsValue().load(std::memory_order_acquire), modified, + on_command_line, counter_); + } } + return nullptr; +} - Write(value); +bool FlagImpl::RestoreState(const FlagState& flag_state) { + absl::MutexLock l(DataGuard()); - { - absl::MutexLock l(DataGuard()); + if (flag_state.counter_ == counter_) { + return false; + } - modified_ = modified; - on_command_line_ = on_command_line; + switch (ValueStorageKind()) { + case FlagValueStorageKind::kAlignedBuffer: + StoreValue(flag_state.value_.heap_allocated); + break; + case FlagValueStorageKind::kOneWordAtomic: + StoreValue(&flag_state.value_.one_word); + break; + case FlagValueStorageKind::kTwoWordsAtomic: + StoreValue(&flag_state.value_.two_words); + 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_. + size_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<int64_t>& FlagImpl::OneWordValue() const { + assert(ValueStorageKind() == FlagValueStorageKind::kOneWordAtomic); + return OffsetValue<FlagOneWordValue>()->value; +} + +std::atomic<AlignedTwoWords>& FlagImpl::TwoWordsValue() const { + assert(ValueStorageKind() == FlagValueStorageKind::kTwoWordsAtomic); + return OffsetValue<FlagTwoWordsValue>()->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 { + 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); + err = absl::StrCat("Illegal value '", value, "' specified for flag '", + Name(), "'", err_sep, parse_err); return nullptr; } @@ -244,32 +430,32 @@ std::unique_ptr<void, DynValueDeleter> FlagImpl::TryParse( } void FlagImpl::Read(void* dst) const { - absl::ReaderMutexLock l(DataGuard()); - - flags_internal::CopyConstruct(op_, value_.dynamic, dst); -} - -void FlagImpl::StoreAtomic() { - size_t data_size = flags_internal::Sizeof(op_); - - if (data_size <= sizeof(int64_t)) { - int64_t t = 0; - std::memcpy(&t, value_.dynamic, data_size); - value_.atomics.small_atomic.store(t, std::memory_order_release); - } -#if defined(ABSL_FLAGS_INTERNAL_ATOMIC_DOUBLE_WORD) - else if (data_size <= sizeof(FlagsInternalTwoWordsType)) { - FlagsInternalTwoWordsType t{0, 0}; - std::memcpy(&t, value_.dynamic, data_size); - value_.atomics.big_atomic.store(t, std::memory_order_release); + auto* guard = DataGuard(); // Make sure flag initialized + switch (ValueStorageKind()) { + case FlagValueStorageKind::kAlignedBuffer: { + absl::MutexLock l(guard); + flags_internal::CopyConstruct(op_, AlignedBufferValue(), dst); + break; + } + 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::kTwoWordsAtomic: { + const AlignedTwoWords two_words_val = + TwoWordsValue().load(std::memory_order_acquire); + std::memcpy(dst, &two_words_val, Sizeof(op_)); + break; + } } -#endif } void FlagImpl::Write(const void* src) { absl::MutexLock l(DataGuard()); - if (ShouldValidateFlagValue(flags_internal::StaticTypeId(op_))) { + if (ShouldValidateFlagValue(flags_internal::FastTypeId(op_))) { std::unique_ptr<void, DynValueDeleter> obj{flags_internal::Clone(op_, src), DynValueDeleter{op_}}; std::string ignored_error; @@ -291,8 +477,8 @@ void FlagImpl::Write(const void* src) { // * 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::SetFromString(absl::string_view value, FlagSettingMode set_mode, - ValueSource source, std::string* err) { +bool FlagImpl::ParseFrom(absl::string_view value, FlagSettingMode set_mode, + ValueSource source, std::string& err) { absl::MutexLock l(DataGuard()); switch (set_mode) { @@ -339,7 +525,7 @@ bool FlagImpl::SetFromString(absl::string_view value, FlagSettingMode set_mode, } if (!modified_) { - // Need to set both default value *and* current, in this case + // Need to set both default value *and* current, in this case. StoreValue(default_value_.dynamic_value); modified_ = false; } @@ -361,7 +547,7 @@ void FlagImpl::CheckDefaultValueParsingRoundtrip() const { ABSL_INTERNAL_LOG( FATAL, absl::StrCat("Flag ", Name(), " (from ", Filename(), - "): std::string form of default value '", v, + "): string form of default value '", v, "' could not be parsed; error=", error)); } |