tvl-depot/absl/flags/internal/flag.cc
Abseil Team b69c7d880c Export of internal Abseil changes
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00f5301405423005d9129935c05f20155536cc1a by CJ Johnson <johnsoncj@google.com>:

Removes usage of std::aligned_storage from Abseil implementation details

PiperOrigin-RevId: 296492301

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fc11d15f91764612fba080669d2381dc181df52b by Abseil Team <absl-team@google.com>:

Fix absl::bind_front documentation.

PiperOrigin-RevId: 296482945

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0164c595c129c46bf21ae74eba5399a1da5f140b by Gennadiy Rozental <rogeeff@google.com>:

Automated g4 rollback of changelist 296320700.

PiperOrigin-RevId: 296439968

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1eb295700758ca0894d872b2de7c675b4ad679af by Abseil Team <absl-team@google.com>:

Removes duplicate comments.

PiperOrigin-RevId: 296433214

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c30c01caae02d2fa4ef783d988de6bebb9757c39 by Derek Mauro <dmauro@google.com>:

Merge GitHub #621: Add RISCV support to GetProgramCounter()

Fixes #621

PiperOrigin-RevId: 296351174

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95d4498167596fd7543e025bdfe9a8da9e2ca3c8 by Abseil Team <absl-team@google.com>:

Automated g4 rollback of changelist 296320700.

PiperOrigin-RevId: 296348701

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b193f0543e0cec54dddb2ed51f45dc489c8d06d5 by Gennadiy Rozental <rogeeff@google.com>:

Change TryParse interface to return managed value.

In addition introduce companion StoreValue routine which consumes pointer to source value and stores the value inside of FlagImpl. In a follow up CL we will change StoreValue implementation to behave differently depending on "value storage kind".
We also rename default_src_ to default_value_.

PiperOrigin-RevId: 296320700

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57e942b485d12912a0a8d0d0b35fa2a62847020f by Derek Mauro <dmauro@google.com>:

Merge GitHub #622
 * Add missing #ifdef conditionals for ABSL_HAVE_VDSO_SUPPORT

PiperOrigin-RevId: 296272830
GitOrigin-RevId: 00f5301405423005d9129935c05f20155536cc1a
Change-Id: I1b05eeaf1280f95fb0a2c5f3654995a87c792893
2020-02-21 15:56:04 -05:00

382 lines
12 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/flag.h"
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <atomic>
#include <memory>
#include <string>
#include <vector>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/const_init.h"
#include "absl/base/optimization.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/flags/usage_config.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
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
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)
#undef DONT_VALIDATE
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_;
};
} // namespace
void FlagImpl::Init() {
new (&data_guard_) absl::Mutex;
absl::MutexLock lock(reinterpret_cast<absl::Mutex*>(&data_guard_));
value_.dynamic = MakeInitValue().release();
StoreAtomic();
}
// 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.
return reinterpret_cast<absl::Mutex*>(&data_guard_);
}
void FlagImpl::AssertValidType(FlagStaticTypeId type_id) const {
FlagStaticTypeId this_type_id = flags_internal::StaticTypeId(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;
void* lhs_runtime_type_id = type_id();
void* rhs_runtime_type_id = this_type_id();
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;
#endif
ABSL_INTERNAL_LOG(
FATAL, absl::StrCat("Flag '", Name(),
"' is defined as one type and declared as another"));
}
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)();
}
return {res, DynValueDeleter{op_}};
}
void FlagImpl::StoreValue(const void* src) {
flags_internal::Copy(op_, src, value_.dynamic);
StoreAtomic();
modified_ = true;
++counter_;
InvokeCallback();
}
absl::string_view FlagImpl::Name() const { return name_; }
std::string FlagImpl::Filename() const {
return flags_internal::GetUsageConfig().normalize_filename(filename_);
}
std::string FlagImpl::Help() const {
return HelpSourceKind() == FlagHelpKind::kLiteral ? help_.literal
: help_.gen_func();
}
bool FlagImpl::IsModified() const {
absl::MutexLock l(DataGuard());
return modified_;
}
bool FlagImpl::IsSpecifiedOnCommandLine() const {
absl::MutexLock l(DataGuard());
return on_command_line_;
}
std::string FlagImpl::DefaultValue() const {
absl::MutexLock l(DataGuard());
auto obj = MakeInitValue();
return flags_internal::Unparse(op_, obj.get());
}
std::string FlagImpl::CurrentValue() const {
absl::MutexLock l(DataGuard());
return flags_internal::Unparse(op_, value_.dynamic);
}
void FlagImpl::SetCallback(const FlagCallbackFunc mutation_callback) {
absl::MutexLock l(DataGuard());
if (callback_ == nullptr) {
callback_ = new FlagCallback;
}
callback_->func = mutation_callback;
InvokeCallback();
}
void FlagImpl::InvokeCallback() const {
if (!callback_) return;
// Make a copy of the C-style function pointer that we are about to invoke
// before we release the lock guarding it.
FlagCallbackFunc cb = callback_->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
// re-locked back after call to callback is completed. Callback invocation is
// guarded by flag's secondary mutex instead which prevents concurrent
// callback invocation. Note that it is possible for other thread to grab the
// primary lock and update flag's value at any time during the callback
// invocation. This is by design. Callback can get a value of the flag if
// necessary, but it might be different from the value initiated the callback
// 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());
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());
if (counter_ == counter) return false;
}
Write(value);
{
absl::MutexLock l(DataGuard());
modified_ = modified;
on_command_line_ = on_command_line;
}
return true;
}
// 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 {
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);
return nullptr;
}
return tentative_value;
}
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);
}
#endif
}
void FlagImpl::Write(const void* src) {
absl::MutexLock l(DataGuard());
if (ShouldValidateFlagValue(flags_internal::StaticTypeId(op_))) {
std::unique_ptr<void, DynValueDeleter> obj{flags_internal::Clone(op_, src),
DynValueDeleter{op_}};
std::string ignored_error;
std::string src_as_str = flags_internal::Unparse(op_, src);
if (!flags_internal::Parse(op_, src_as_str, obj.get(), &ignored_error)) {
ABSL_INTERNAL_LOG(ERROR, absl::StrCat("Attempt to set flag '", Name(),
"' to invalid value ", src_as_str));
}
}
StoreValue(src);
}
// Sets the value of the flag based on specified string `value`. If the flag
// was successfully set to new value, it returns true. Otherwise, sets `err`
// to indicate the error, leaves the flag unchanged, and returns false. There
// are three ways to set the flag's value:
// * Update the current flag value
// * 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) {
absl::MutexLock l(DataGuard());
switch (set_mode) {
case SET_FLAGS_VALUE: {
// set or modify the flag's value
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
if (source == kCommandLine) {
on_command_line_ = true;
}
break;
}
case SET_FLAG_IF_DEFAULT: {
// set the flag's value, but only if it hasn't been set by someone else
if (modified_) {
// TODO(rogeeff): review and fix this semantic. Currently we do not fail
// in this case if flag is modified. This is misleading since the flag's
// value is not updated even though we return true.
// *err = absl::StrCat(Name(), " is already set to ",
// CurrentValue(), "\n");
// return false;
return true;
}
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
StoreValue(tentative_value.get());
break;
}
case SET_FLAGS_DEFAULT: {
auto tentative_value = TryParse(value, err);
if (!tentative_value) return false;
if (DefaultKind() == FlagDefaultKind::kDynamicValue) {
void* old_value = default_value_.dynamic_value;
default_value_.dynamic_value = tentative_value.release();
tentative_value.reset(old_value);
} else {
default_value_.dynamic_value = tentative_value.release();
def_kind_ = static_cast<uint8_t>(FlagDefaultKind::kDynamicValue);
}
if (!modified_) {
// Need to set both default value *and* current, in this case
StoreValue(default_value_.dynamic_value);
modified_ = false;
}
break;
}
}
return true;
}
void FlagImpl::CheckDefaultValueParsingRoundtrip() const {
std::string v = DefaultValue();
absl::MutexLock lock(DataGuard());
auto dst = MakeInitValue();
std::string error;
if (!flags_internal::Parse(op_, v, dst.get(), &error)) {
ABSL_INTERNAL_LOG(
FATAL,
absl::StrCat("Flag ", Name(), " (from ", Filename(),
"): std::string form of default value '", v,
"' could not be parsed; error=", error));
}
// We do not compare dst to def since parsing/unparsing may make
// small changes, e.g., precision loss for floating point types.
}
bool FlagImpl::ValidateInputValue(absl::string_view value) const {
absl::MutexLock l(DataGuard());
auto obj = MakeInitValue();
std::string ignored_error;
return flags_internal::Parse(op_, value, obj.get(), &ignored_error);
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl