tvl-depot/absl/flags/internal/registry.cc
Abseil Team 83c1d65c90 Export of internal Abseil changes
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972333fe1e43427849b8a634aa35061e81be3642 by Abseil Team <absl-team@google.com>:

Replace deprecated thread annotations macros.

PiperOrigin-RevId: 267332619

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7039c6dc499a31c372b4872eda0772455931c360 by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 267220271

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a3f524d2afc2535686f206a7ce06961016349d7a by Abseil Team <absl-team@google.com>:

Factor kernel_timeout out of synchronization.

PiperOrigin-RevId: 267217304

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90287de4114ef9a06cafe50256a2d03349772c21 by Abseil Team <absl-team@google.com>:

Fixed comment typo.

PiperOrigin-RevId: 267198532

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d312c1a1e52aeca1871ff0deead416d09a7f237e by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 267185804
GitOrigin-RevId: 972333fe1e43427849b8a634aa35061e81be3642
Change-Id: Ia8a2f877c57cef9854aad48f1753af872fc04dc8
2019-09-05 06:05:17 -04:00

404 lines
13 KiB
C++

//
// 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/registry.h"
#include "absl/base/dynamic_annotations.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/flags/config.h"
#include "absl/flags/usage_config.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
// --------------------------------------------------------------------
// FlagRegistry implementation
// A FlagRegistry holds all flag objects indexed
// by their names so that if you know a flag's name you can access or
// set it.
namespace absl {
namespace flags_internal {
// --------------------------------------------------------------------
// FlagRegistry
// A FlagRegistry singleton object holds all flag objects indexed
// by their names so that if you know a flag's name (as a C
// string), you can access or set it. If the function is named
// FooLocked(), you must own the registry lock before calling
// the function; otherwise, you should *not* hold the lock, and
// the function will acquire it itself if needed.
// --------------------------------------------------------------------
class FlagRegistry {
public:
FlagRegistry() = default;
~FlagRegistry() {
for (auto& p : flags_) {
p.second->Destroy();
}
}
// Store a flag in this registry. Takes ownership of *flag.
void RegisterFlag(CommandLineFlag* flag);
void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }
void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }
// Returns the flag object for the specified name, or nullptr if not found.
// Will emit a warning if a 'retired' flag is specified.
CommandLineFlag* FindFlagLocked(absl::string_view name);
// Returns the retired flag object for the specified name, or nullptr if not
// found or not retired. Does not emit a warning.
CommandLineFlag* FindRetiredFlagLocked(absl::string_view name);
static FlagRegistry* GlobalRegistry(); // returns a singleton registry
private:
friend class FlagSaverImpl; // reads all the flags in order to copy them
friend void ForEachFlagUnlocked(
std::function<void(CommandLineFlag*)> visitor);
// The map from name to flag, for FindFlagLocked().
using FlagMap = std::map<absl::string_view, CommandLineFlag*>;
using FlagIterator = FlagMap::iterator;
using FlagConstIterator = FlagMap::const_iterator;
FlagMap flags_;
absl::Mutex lock_;
// Disallow
FlagRegistry(const FlagRegistry&);
FlagRegistry& operator=(const FlagRegistry&);
};
FlagRegistry* FlagRegistry::GlobalRegistry() {
static FlagRegistry* global_registry = new FlagRegistry;
return global_registry;
}
namespace {
class FlagRegistryLock {
public:
explicit FlagRegistryLock(FlagRegistry* fr) : fr_(fr) { fr_->Lock(); }
~FlagRegistryLock() { fr_->Unlock(); }
private:
FlagRegistry* const fr_;
};
} // namespace
void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
FlagRegistryLock registry_lock(this);
std::pair<FlagIterator, bool> ins =
flags_.insert(FlagMap::value_type(flag->Name(), flag));
if (ins.second == false) { // means the name was already in the map
CommandLineFlag* old_flag = ins.first->second;
if (flag->IsRetired() != old_flag->IsRetired()) {
// All registrations must agree on the 'retired' flag.
flags_internal::ReportUsageError(
absl::StrCat(
"Retired flag '", flag->Name(),
"' was defined normally in file '",
(flag->IsRetired() ? old_flag->Filename() : flag->Filename()),
"'."),
true);
} else if (flag->op_ != old_flag->op_) {
flags_internal::ReportUsageError(
absl::StrCat("Flag '", flag->Name(),
"' was defined more than once but with "
"differing types. Defined in files '",
old_flag->Filename(), "' and '", flag->Filename(),
"' with types '", old_flag->Typename(), "' and '",
flag->Typename(), "', respectively."),
true);
} else if (old_flag->IsRetired()) {
// Retired definitions are idempotent. Just keep the old one.
flag->Destroy();
return;
} else if (old_flag->Filename() != flag->Filename()) {
flags_internal::ReportUsageError(
absl::StrCat("Flag '", flag->Name(),
"' was defined more than once (in files '",
old_flag->Filename(), "' and '", flag->Filename(),
"')."),
true);
} else {
flags_internal::ReportUsageError(
absl::StrCat(
"Something wrong with flag '", flag->Name(), "' in file '",
flag->Filename(), "'. One possibility: file '", flag->Filename(),
"' is being linked both statically and dynamically into this "
"executable. e.g. some files listed as srcs to a test and also "
"listed as srcs of some shared lib deps of the same test."),
true);
}
// All cases above are fatal, except for the retired flags.
std::exit(1);
}
}
CommandLineFlag* FlagRegistry::FindFlagLocked(absl::string_view name) {
FlagConstIterator i = flags_.find(name);
if (i == flags_.end()) {
return nullptr;
}
if (i->second->IsRetired()) {
flags_internal::ReportUsageError(
absl::StrCat("Accessing retired flag '", name, "'"), false);
}
return i->second;
}
CommandLineFlag* FlagRegistry::FindRetiredFlagLocked(absl::string_view name) {
FlagConstIterator i = flags_.find(name);
if (i == flags_.end() || !i->second->IsRetired()) {
return nullptr;
}
return i->second;
}
// --------------------------------------------------------------------
// FlagSaver
// FlagSaverImpl
// This class stores the states of all flags at construct time,
// and restores all flags to that state at destruct time.
// Its major implementation challenge is that it never modifies
// pointers in the 'main' registry, so global FLAG_* vars always
// point to the right place.
// --------------------------------------------------------------------
class FlagSaverImpl {
public:
// Constructs an empty FlagSaverImpl object.
FlagSaverImpl() {}
~FlagSaverImpl() {
// reclaim memory from each of our CommandLineFlags
for (const SavedFlag& src : backup_registry_) {
Delete(src.op, src.current);
Delete(src.op, src.default_value);
}
}
// Saves the flag states from the flag registry into this object.
// It's an error to call this more than once.
// Must be called when the registry mutex is not held.
void SaveFromRegistry() {
assert(backup_registry_.empty()); // call only once!
SavedFlag saved;
flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
if (flag->IsRetired()) return;
saved.name = flag->Name();
saved.op = flag->op_;
saved.marshalling_op = flag->marshalling_op_;
{
absl::MutexLock l(flag->InitFlagIfNecessary());
saved.validator = flag->GetValidator();
saved.modified = flag->modified_;
saved.on_command_line = flag->on_command_line_;
saved.current = Clone(saved.op, flag->cur_);
saved.default_value = Clone(saved.op, flag->def_);
saved.counter = flag->counter_;
}
backup_registry_.push_back(saved);
});
}
// Restores the saved flag states into the flag registry. We
// assume no flags were added or deleted from the registry since
// the SaveFromRegistry; if they were, that's trouble! Must be
// called when the registry mutex is not held.
void RestoreToRegistry() {
FlagRegistry* const global_registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(global_registry);
for (const SavedFlag& src : backup_registry_) {
CommandLineFlag* flag = global_registry->FindFlagLocked(src.name);
// If null, flag got deleted from registry.
if (!flag) continue;
bool restored = false;
{
// This function encapsulate the lock.
flag->SetValidator(src.validator);
absl::MutexLock l(flag->InitFlagIfNecessary());
flag->modified_ = src.modified;
flag->on_command_line_ = src.on_command_line;
if (flag->counter_ != src.counter ||
ChangedDirectly(flag, src.default_value, flag->def_)) {
restored = true;
Copy(src.op, src.default_value, flag->def_);
}
if (flag->counter_ != src.counter ||
ChangedDirectly(flag, src.current, flag->cur_)) {
restored = true;
Copy(src.op, src.current, flag->cur_);
UpdateCopy(flag);
flag->InvokeCallback();
}
}
if (restored) {
flag->counter_++;
// Revalidate the flag because the validator might store state based
// on the flag's value, which just changed due to the restore.
// Failing validation is ignored because it's assumed that the flag
// was valid previously and there's little that can be done about it
// here, anyway.
flag->ValidateInputValue(flag->CurrentValue());
ABSL_INTERNAL_LOG(
INFO, absl::StrCat("Restore saved value of ", flag->Name(), ": ",
Unparse(src.marshalling_op, src.current)));
}
}
}
private:
struct SavedFlag {
absl::string_view name;
FlagOpFn op;
FlagMarshallingOpFn marshalling_op;
int64_t counter;
void* validator;
bool modified;
bool on_command_line;
const void* current; // nullptr after restore
const void* default_value; // nullptr after restore
};
std::vector<SavedFlag> backup_registry_;
FlagSaverImpl(const FlagSaverImpl&); // no copying!
void operator=(const FlagSaverImpl&);
};
FlagSaver::FlagSaver() : impl_(new FlagSaverImpl()) {
impl_->SaveFromRegistry();
}
void FlagSaver::Ignore() {
delete impl_;
impl_ = nullptr;
}
FlagSaver::~FlagSaver() {
if (!impl_) return;
impl_->RestoreToRegistry();
delete impl_;
}
// --------------------------------------------------------------------
CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
if (name.empty()) return nullptr;
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
return registry->FindFlagLocked(name);
}
CommandLineFlag* FindRetiredFlag(absl::string_view name) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
return registry->FindRetiredFlagLocked(name);
}
// --------------------------------------------------------------------
void ForEachFlagUnlocked(std::function<void(CommandLineFlag*)> visitor) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
for (FlagRegistry::FlagConstIterator i = registry->flags_.begin();
i != registry->flags_.end(); ++i) {
visitor(i->second);
}
}
void ForEachFlag(std::function<void(CommandLineFlag*)> visitor) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
ForEachFlagUnlocked(visitor);
}
// --------------------------------------------------------------------
bool RegisterCommandLineFlag(CommandLineFlag* flag) {
FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
return true;
}
// --------------------------------------------------------------------
namespace {
class RetiredFlagObj final : public flags_internal::CommandLineFlag {
public:
constexpr RetiredFlagObj(const char* name, FlagOpFn ops,
FlagMarshallingOpFn marshalling_ops)
: flags_internal::CommandLineFlag(
name, flags_internal::HelpText::FromStaticCString(nullptr),
/*filename=*/"RETIRED", ops, marshalling_ops,
/*initial_value_gen=*/nullptr,
/*def=*/nullptr,
/*cur=*/nullptr) {}
private:
bool IsRetired() const override { return true; }
void Destroy() const override {
// Values are heap allocated for Retired Flags.
if (cur_) Delete(op_, cur_);
if (def_) Delete(op_, def_);
if (locks_) delete locks_;
delete this;
}
};
} // namespace
bool Retire(const char* name, FlagOpFn ops,
FlagMarshallingOpFn marshalling_ops) {
auto* flag = new flags_internal::RetiredFlagObj(name, ops, marshalling_ops);
FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
return true;
}
// --------------------------------------------------------------------
bool IsRetiredFlag(absl::string_view name, bool* type_is_bool) {
assert(!name.empty());
CommandLineFlag* flag = flags_internal::FindRetiredFlag(name);
if (flag == nullptr) {
return false;
}
assert(type_is_bool);
*type_is_bool = flag->IsOfType<bool>();
return true;
}
} // namespace flags_internal
} // namespace absl