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Export of internal Abseil changes

Browse source 
--
c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>:

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

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68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>:

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

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ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>:

Change null-term* (and nul-term*) to NUL-term* in comments

PiperOrigin-RevId: 285036610

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729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>:

Use the Posix implementation of thread identity on MinGW.
Some versions of MinGW suffer from thread_local bugs.

PiperOrigin-RevId: 285022920

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39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>:

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
This commit is contained in:
Abseil Team 2019-12-12 10:36:03 -08:00 • committed by Matt Calabrese
parent 1e39f8626a
commit 12bc53e031
339 changed files with 948 additions and 82 deletions
Download patch file Download diff file Expand all files Collapse all files

52
absl/flags/internal/flag.h
View file

@ -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 <typename T>
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<void, DynValueDeleter> 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<bool> 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<int64_t> 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
struct CallbackData {
FlagCallback func;
absl::Mutex guard; // Guard for concurrent callback invocations.
};
CommandLineFlagLocks* locks_ = nullptr; // locks, laziliy allocated.
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<T> type.
@ -354,7 +357,7 @@ class Flag final : public flags_internal::CommandLineFlag {
private:
friend class FlagState<T>;
void Destroy() const override { impl_.Destroy(); }
void Destroy() override { impl_.Destroy(); }
void Read(void* dst) const override {
impl_.Read(*this, dst, &flags_internal::FlagOps<T>);
@ -414,6 +417,7 @@ T* MakeFromDefaultValue(EmptyBraces) {
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_FLAG_H_