From 12bc53e0318d80569270a5b26ccbc62b52022b89 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Thu, 12 Dec 2019 10:36:03 -0800 Subject: Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro : Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental : This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck : Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro : Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon : Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1 --- absl/flags/internal/commandlineflag.cc | 2 + absl/flags/internal/commandlineflag.h | 4 +- absl/flags/internal/flag.cc | 113 ++++++++++++++++++++++----------- absl/flags/internal/flag.h | 54 ++++++++-------- absl/flags/internal/parse.h | 2 + absl/flags/internal/path_util.h | 2 + absl/flags/internal/program_name.cc | 2 + absl/flags/internal/program_name.h | 2 + absl/flags/internal/registry.cc | 4 +- absl/flags/internal/registry.h | 2 + absl/flags/internal/type_erased.cc | 2 + absl/flags/internal/type_erased.h | 2 + absl/flags/internal/usage.cc | 2 + absl/flags/internal/usage.h | 2 + 14 files changed, 130 insertions(+), 65 deletions(-) (limited to 'absl/flags/internal') diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/internal/commandlineflag.cc index 88f91e16..09249274 100644 --- a/absl/flags/internal/commandlineflag.cc +++ b/absl/flags/internal/commandlineflag.cc @@ -18,6 +18,7 @@ #include "absl/flags/usage_config.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // The help message indicating that the commandline flag has been @@ -57,4 +58,5 @@ std::string CommandLineFlag::Filename() const { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/commandlineflag.h b/absl/flags/internal/commandlineflag.h index 7964f1bf..49e13d1e 100644 --- a/absl/flags/internal/commandlineflag.h +++ b/absl/flags/internal/commandlineflag.h @@ -23,6 +23,7 @@ #include "absl/types/optional.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // Type-specific operations, eg., parsing, copying, etc. are provided @@ -158,7 +159,7 @@ class CommandLineFlag { : name_(name), filename_(filename) {} // Virtual destructor - virtual void Destroy() const = 0; + virtual void Destroy() = 0; // Not copyable/assignable. CommandLineFlag(const CommandLineFlag&) = delete; @@ -280,6 +281,7 @@ class CommandLineFlag { A(float) } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_ diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc index 435cc362..599bd7a4 100644 --- a/absl/flags/internal/flag.cc +++ b/absl/flags/internal/flag.cc @@ -19,6 +19,7 @@ #include "absl/synchronization/mutex.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { namespace { @@ -34,20 +35,40 @@ bool ShouldValidateFlagValue(const CommandLineFlag& flag) { 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_; +}; + +// This global lock guards the initialization and destruction of data_guard_, +// which is used to guard the other Flag data. +ABSL_CONST_INIT static absl::Mutex flag_mutex_lifetime_guard(absl::kConstInit); + } // namespace void FlagImpl::Init() { - ABSL_CONST_INIT static absl::Mutex init_lock(absl::kConstInit); - { - absl::MutexLock lock(&init_lock); + absl::MutexLock lock(&flag_mutex_lifetime_guard); - if (locks_ == nullptr) { // Must initialize Mutexes for this flag. - locks_ = new FlagImpl::CommandLineFlagLocks; + // Must initialize data guard for this flag. + if (!is_data_guard_inited_) { + new (&data_guard_) absl::Mutex; + is_data_guard_inited_ = true; } } - absl::MutexLock lock(&locks_->primary_mu); + absl::MutexLock lock(reinterpret_cast(&data_guard_)); if (cur_ != nullptr) { inited_.store(true, std::memory_order_release); @@ -67,21 +88,29 @@ absl::Mutex* FlagImpl::DataGuard() const { const_cast(this)->Init(); } - // All fields initialized; locks_ is therefore safe to read. - return &locks_->primary_mu; + // data_guard_ is initialized. + return reinterpret_cast(&data_guard_); } -void FlagImpl::Destroy() const { +void FlagImpl::Destroy() { { absl::MutexLock l(DataGuard()); // Values are heap allocated for Abseil Flags. if (cur_) Delete(op_, cur_); - if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) + + // Release the dynamically allocated default value if any. + if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) { Delete(op_, default_src_.dynamic_value); + } + + // If this flag has an assigned callback, release callback data. + if (callback_data_) delete callback_data_; } - delete locks_; + absl::MutexLock l(&flag_mutex_lifetime_guard); + DataGuard()->~Mutex(); + is_data_guard_inited_ = false; } std::unique_ptr FlagImpl::MakeInitValue() const { @@ -126,13 +155,20 @@ void FlagImpl::SetCallback( const flags_internal::FlagCallback mutation_callback) { absl::MutexLock l(DataGuard()); - callback_ = mutation_callback; + if (callback_data_ == nullptr) { + callback_data_ = new CallbackData; + } + callback_data_->func = mutation_callback; InvokeCallback(); } void FlagImpl::InvokeCallback() const { - if (!callback_) return; + if (!callback_data_) return; + + // Make a copy of the C-style function pointer that we are about to invoke + // before we release the lock guarding it. + FlagCallback cb = callback_data_->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 @@ -145,14 +181,9 @@ 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. - DataGuard()->Unlock(); - - { - absl::MutexLock lock(&locks_->callback_mu); - callback_(); - } - - DataGuard()->Lock(); + MutexRelock relock(DataGuard()); + absl::MutexLock lock(&callback_data_->guard); + cb(); } bool FlagImpl::RestoreState(const CommandLineFlag& flag, const void* value, @@ -177,12 +208,13 @@ bool FlagImpl::RestoreState(const CommandLineFlag& flag, const void* value, } // Attempts to parse supplied `value` string using parsing routine in the `flag` -// argument. If parsing successful, this function stores the parsed value in -// 'dst' assuming it is a pointer to the flag's value type. In case if any error -// is encountered in either step, the error message is stored in 'err' -bool FlagImpl::TryParse(const CommandLineFlag& flag, void* dst, +// 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' +bool FlagImpl::TryParse(const CommandLineFlag& flag, void** dst, absl::string_view value, std::string* err) const { auto tentative_value = MakeInitValue(); + std::string parse_err; if (!Parse(marshalling_op_, value, tentative_value.get(), &parse_err)) { auto type_name = flag.Typename(); @@ -194,7 +226,10 @@ bool FlagImpl::TryParse(const CommandLineFlag& flag, void* dst, return false; } - Copy(op_, tentative_value.get(), dst); + void* old_val = *dst; + *dst = tentative_value.release(); + tentative_value.reset(old_val); + return true; } @@ -274,7 +309,7 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag, switch (set_mode) { case SET_FLAGS_VALUE: { // set or modify the flag's value - if (!TryParse(flag, cur_, value, err)) return false; + if (!TryParse(flag, &cur_, value, err)) return false; modified_ = true; counter_++; StoreAtomic(); @@ -288,7 +323,7 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag, case SET_FLAG_IF_DEFAULT: { // set the flag's value, but only if it hasn't been set by someone else if (!modified_) { - if (!TryParse(flag, cur_, value, err)) return false; + if (!TryParse(flag, &cur_, value, err)) return false; modified_ = true; counter_++; StoreAtomic(); @@ -305,18 +340,19 @@ bool FlagImpl::SetFromString(const CommandLineFlag& flag, break; } case SET_FLAGS_DEFAULT: { - // Flag's new default-value. - auto new_default_value = MakeInitValue(); - - if (!TryParse(flag, new_default_value.get(), value, err)) return false; - if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) { - // Release old default value. - Delete(op_, default_src_.dynamic_value); - } + if (!TryParse(flag, &default_src_.dynamic_value, value, err)) { + return false; + } + } else { + void* new_default_val = nullptr; + if (!TryParse(flag, &new_default_val, value, err)) { + return false; + } - default_src_.dynamic_value = new_default_value.release(); - def_kind_ = FlagDefaultSrcKind::kDynamicValue; + default_src_.dynamic_value = new_default_val; + def_kind_ = FlagDefaultSrcKind::kDynamicValue; + } if (!modified_) { // Need to set both default value *and* current, in this case @@ -361,4 +397,5 @@ bool FlagImpl::ValidateInputValue(absl::string_view value) const { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h index 947a8cad..20de406f 100644 --- a/absl/flags/internal/flag.h +++ b/absl/flags/internal/flag.h @@ -27,6 +27,7 @@ #include "absl/synchronization/mutex.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { constexpr int64_t AtomicInit() { return 0xababababababababll; } @@ -156,10 +157,11 @@ class FlagImpl { help_(help.source), help_source_kind_(help.kind), def_kind_(flags_internal::FlagDefaultSrcKind::kGenFunc), - default_src_(default_value_gen) {} + default_src_(default_value_gen), + data_guard_{} {} // Forces destruction of the Flag's data. - void Destroy() const; + void Destroy(); // Constant access methods std::string Help() const; @@ -170,9 +172,10 @@ class FlagImpl { void Read(const CommandLineFlag& flag, void* dst, const flags_internal::FlagOpFn dst_op) const ABSL_LOCKS_EXCLUDED(*DataGuard()); - // Attempts to parse supplied `value` std::string. - bool TryParse(const CommandLineFlag& flag, void* dst, absl::string_view value, - std::string* err) const + // Attempts to parse supplied `value` std::string. If parsing is successful, then + // it replaces `dst` with the new value. + bool TryParse(const CommandLineFlag& flag, void** dst, + absl::string_view value, std::string* err) const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); template bool AtomicGet(T* v) const { @@ -226,8 +229,7 @@ class FlagImpl { void Init(); // Ensures that the lazily initialized data is initialized, // and returns pointer to the mutex guarding flags data. - absl::Mutex* DataGuard() const ABSL_LOCK_RETURNED(locks_->primary_mu); - + absl::Mutex* DataGuard() const ABSL_LOCK_RETURNED((absl::Mutex*)&data_guard_); // Returns heap allocated value of type T initialized with default value. std::unique_ptr MakeInitValue() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); @@ -239,9 +241,12 @@ class FlagImpl { // Indicates if help message was supplied as literal or generator func. const FlagHelpSrcKind help_source_kind_; - // Mutable Flag's data. (guarded by DataGuard()). - // Indicates that locks_ and cur_ fields have been lazily initialized. + // Indicates that the Flag state is initialized. std::atomic inited_{false}; + // Mutable Flag state (guarded by data_guard_). + // Additional bool to protect against multiple concurrent constructions + // of `data_guard_`. + bool is_data_guard_inited_ = false; // Has flag value been modified? bool modified_ ABSL_GUARDED_BY(*DataGuard()) = false; // Specified on command line. @@ -261,22 +266,20 @@ class FlagImpl { // For some types, a copy of the current value is kept in an atomically // accessible field. std::atomic atomic_{flags_internal::AtomicInit()}; - // Mutation callback - FlagCallback callback_ = nullptr; - - // Lazily initialized mutexes for this flag value. We cannot inline a - // SpinLock or Mutex here because those have non-constexpr constructors and - // so would prevent constant initialization of this type. - // TODO(rogeeff): fix it once Mutex has constexpr constructor - // The following struct contains the locks in a CommandLineFlag struct. - // They are in a separate struct that is lazily allocated to avoid problems - // with static initialization and to avoid multiple allocations. - struct CommandLineFlagLocks { - absl::Mutex primary_mu; // protects several fields in CommandLineFlag - absl::Mutex callback_mu; // used to serialize callbacks - }; - CommandLineFlagLocks* locks_ = nullptr; // locks, laziliy allocated. + struct CallbackData { + FlagCallback func; + absl::Mutex guard; // Guard for concurrent callback invocations. + }; + CallbackData* callback_data_ ABSL_GUARDED_BY(*DataGuard()) = nullptr; + // 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)]; }; // This is "unspecified" implementation of absl::Flag type. @@ -354,7 +357,7 @@ class Flag final : public flags_internal::CommandLineFlag { private: friend class FlagState; - void Destroy() const override { impl_.Destroy(); } + void Destroy() override { impl_.Destroy(); } void Read(void* dst) const override { impl_.Read(*this, dst, &flags_internal::FlagOps); @@ -414,6 +417,7 @@ T* MakeFromDefaultValue(EmptyBraces) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_FLAG_H_ diff --git a/absl/flags/internal/parse.h b/absl/flags/internal/parse.h index fd3aca61..e534635b 100644 --- a/absl/flags/internal/parse.h +++ b/absl/flags/internal/parse.h @@ -27,6 +27,7 @@ ABSL_DECLARE_FLAG(std::vector, tryfromenv); ABSL_DECLARE_FLAG(std::vector, undefok); namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { enum class ArgvListAction { kRemoveParsedArgs, kKeepParsedArgs }; @@ -43,6 +44,7 @@ std::vector ParseCommandLineImpl(int argc, char* argv[], OnUndefinedFlag on_undef_flag); } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_PARSE_H_ diff --git a/absl/flags/internal/path_util.h b/absl/flags/internal/path_util.h index 5615c0e6..41696377 100644 --- a/absl/flags/internal/path_util.h +++ b/absl/flags/internal/path_util.h @@ -20,6 +20,7 @@ #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 @@ -55,6 +56,7 @@ inline absl::string_view Package(absl::string_view filename) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_PATH_UTIL_H_ diff --git a/absl/flags/internal/program_name.cc b/absl/flags/internal/program_name.cc index f0811f14..df0c3309 100644 --- a/absl/flags/internal/program_name.cc +++ b/absl/flags/internal/program_name.cc @@ -21,6 +21,7 @@ #include "absl/synchronization/mutex.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { ABSL_CONST_INIT static absl::Mutex program_name_guard(absl::kConstInit); @@ -50,4 +51,5 @@ void SetProgramInvocationName(absl::string_view prog_name_str) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/program_name.h b/absl/flags/internal/program_name.h index 326f24bb..317a7c5c 100644 --- a/absl/flags/internal/program_name.h +++ b/absl/flags/internal/program_name.h @@ -24,6 +24,7 @@ // Program name namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // Returns program invocation name or "UNKNOWN" if `SetProgramInvocationName()` @@ -42,6 +43,7 @@ std::string ShortProgramInvocationName(); void SetProgramInvocationName(absl::string_view prog_name_str); } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_PROGRAM_NAME_H_ diff --git a/absl/flags/internal/registry.cc b/absl/flags/internal/registry.cc index 52d9f3c7..5eae933c 100644 --- a/absl/flags/internal/registry.cc +++ b/absl/flags/internal/registry.cc @@ -30,6 +30,7 @@ // set it. namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // -------------------------------------------------------------------- @@ -281,7 +282,7 @@ class RetiredFlagObj final : public flags_internal::CommandLineFlag { op_(ops) {} private: - void Destroy() const override { + void Destroy() override { // Values are heap allocated for Retired Flags. delete this; } @@ -336,4 +337,5 @@ bool IsRetiredFlag(absl::string_view name, bool* type_is_bool) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h index 1889f3a0..d2145a8a 100644 --- a/absl/flags/internal/registry.h +++ b/absl/flags/internal/registry.h @@ -27,6 +27,7 @@ // Global flags registry API. namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { CommandLineFlag* FindCommandLineFlag(absl::string_view name); @@ -115,6 +116,7 @@ class FlagSaver { }; } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_REGISTRY_H_ diff --git a/absl/flags/internal/type_erased.cc b/absl/flags/internal/type_erased.cc index a1650fcf..7910db8f 100644 --- a/absl/flags/internal/type_erased.cc +++ b/absl/flags/internal/type_erased.cc @@ -21,6 +21,7 @@ #include "absl/strings/str_cat.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { bool GetCommandLineOption(absl::string_view name, std::string* value) { @@ -79,4 +80,5 @@ bool SpecifiedOnCommandLine(absl::string_view name) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/type_erased.h b/absl/flags/internal/type_erased.h index a9551166..6cbd84cd 100644 --- a/absl/flags/internal/type_erased.h +++ b/absl/flags/internal/type_erased.h @@ -25,6 +25,7 @@ // Registry interfaces operating on type erased handles. namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // If a flag named "name" exists, store its current value in *OUTPUT @@ -81,6 +82,7 @@ inline bool GetByName(absl::string_view name, T* dst) { } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_FLAGS_INTERNAL_TYPE_ERASED_H_ diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc index dc12e32f..4602c019 100644 --- a/absl/flags/internal/usage.cc +++ b/absl/flags/internal/usage.cc @@ -44,6 +44,7 @@ ABSL_FLAG(std::string, helpmatch, "", "show help on modules whose name contains the specified substr"); namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { namespace { @@ -404,4 +405,5 @@ int HandleUsageFlags(std::ostream& out, } } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h index 76075b08..5e8ca6a1 100644 --- a/absl/flags/internal/usage.h +++ b/absl/flags/internal/usage.h @@ -27,6 +27,7 @@ // Usage reporting interfaces namespace absl { +ABSL_NAMESPACE_BEGIN namespace flags_internal { // The format to report the help messages in. @@ -64,6 +65,7 @@ int HandleUsageFlags(std::ostream& out, absl::string_view program_usage_message); } // namespace flags_internal +ABSL_NAMESPACE_END } // namespace absl ABSL_DECLARE_FLAG(bool, help); -- cgit v1.2.3