tvl-depot/absl/flags/internal/commandlineflag.cc

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Export of internal Abseil changes. -- 78293ba4eb4981991ae7e6edd25eb9245fcd7515 by Andy Soffer <asoffer@google.com>: internal changes PiperOrigin-RevId: 247073879 -- 7bd97e3aad0c3012b89a39392a6ad3f254e9f3c3 by Derek Mauro <dmauro@google.com>: Release commandline flags PiperOrigin-RevId: 247065920 -- 2a991849fd7b140a43b073076d194b61533fd199 by Tom Manshreck <shreck@google.com>: Add documentation for built-in usage flags PiperOrigin-RevId: 247058863 -- 14157b0de45841706bbd631284191fd94c313db9 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 247058292 -- ed67e0a80468596e30540b367727a250fa415b68 by Abseil Team <absl-team@google.com>: Internal Change. PiperOrigin-RevId: 246828655 -- e1bc8c2aa3f90b3d56c55c5b7244e718c919265d by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 246822325 -- 907a68f287199f749cb9bdb48571b50bc34731e1 by Eric Fiselier <ericwf@google.com>: Accept vector<bool>::reference in StrCat and friends. Converting vector<bool>::reference to alphanum requires two user defined conversions, which isn't allowed. In order to accept this, we need a special constructor that is only enabled for the bool proxy types. PiperOrigin-RevId: 246626732 -- fe4295fa95cc65dee8c881ba12dd8f516e68c40d by Abseil Team <absl-team@google.com>: Clarify the proper way to define AbslHashValue, and fix confusing indentation. PiperOrigin-RevId: 246406528 -- d7174681a72d4a25c8fd2b4d9f515a0763eff87c by Gennadiy Rozental <rogeeff@google.com>: Internal change PiperOrigin-RevId: 246358214 -- a7fdc19683cf1a5885e9e1af52fcdb2db1eda53b by Abseil Team <absl-team@google.com>: Fix sample template instantiation. PiperOrigin-RevId: 246354617 -- 29a23c6835f872948d09b24d890385bf195bc995 by Abseil Team <absl-team@google.com>: Fix incorrectly copy-pasted static_assert in absl::optional::value_or The static_assert for a move-constructible type previously said the type must be copy-constructible. PiperOrigin-RevId: 246313827 -- 41884d5872d4ea2c67875b00144b8c8a5859a295 by Greg Falcon <gfalcon@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 245418790 -- 7f90a7f94cdd5e21232c749efe952a750b5c43a2 by Abseil Team <absl-team@google.com>: Internal change PiperOrigin-RevId: 245412658 -- 730a329cf047d54b46971fce1781edd857208c2a by Greg Falcon <gfalcon@google.com>: internal change PiperOrigin-RevId: 245293234 -- cf0216be6338200cbb18167d3f3b2e98e372be77 by Greg Falcon <gfalcon@google.com>: Internal change PiperOrigin-RevId: 245288164 GitOrigin-RevId: 78293ba4eb4981991ae7e6edd25eb9245fcd7515 Change-Id: I5ea9a852c36c722bae2d6be65fb7f72473d94ab6
2019-05-07 21:56:42 +02:00
//
// 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/commandlineflag.h"
#include <cassert>
#include "absl/base/internal/raw_logging.h"
#include "absl/base/optimization.h"
#include "absl/flags/config.h"
#include "absl/flags/usage_config.h"
#include "absl/strings/str_cat.h"
#include "absl/synchronization/mutex.h"
namespace absl {
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
// This is used by this file, and also in commandlineflags_reporting.cc
const char kStrippedFlagHelp[] = "\001\002\003\004 (unknown) \004\003\002\001";
namespace {
void StoreAtomic(CommandLineFlag* flag, const void* data, size_t size) {
int64_t t = 0;
assert(size <= sizeof(int64_t));
memcpy(&t, data, size);
flag->atomic.store(t, std::memory_order_release);
}
// 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.
void InvokeCallback(CommandLineFlag* flag, absl::Mutex* primary_lock)
EXCLUSIVE_LOCKS_REQUIRED(primary_lock) {
if (!flag->callback) return;
// The callback lock is guaranteed initialized, because *primary_lock exists.
absl::Mutex* callback_mu = &flag->locks->callback_mu;
// When executing the callback we need the primary flag's mutex to be unlocked
// so that callback can retrieve the flag's value.
primary_lock->Unlock();
{
absl::MutexLock lock(callback_mu);
flag->callback();
}
primary_lock->Lock();
}
// Currently we only validate flag values for user-defined flag types.
bool ShouldValidateFlagValue(const CommandLineFlag& flag) {
#define DONT_VALIDATE(T) \
if (flag.IsOfType<T>()) return false;
ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(DONT_VALIDATE)
DONT_VALIDATE(std::string)
DONT_VALIDATE(std::vector<std::string>)
#undef DONT_VALIDATE
return true;
}
} // namespace
// Update any copy of the flag value that is stored in an atomic word.
// In addition if flag has a mutation callback this function invokes it.
void UpdateCopy(CommandLineFlag* flag, absl::Mutex* primary_lock)
EXCLUSIVE_LOCKS_REQUIRED(primary_lock) {
#define STORE_ATOMIC(T) \
else if (flag->IsOfType<T>()) { \
StoreAtomic(flag, flag->cur, sizeof(T)); \
}
if (false) {
}
ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(STORE_ATOMIC)
#undef STORE_ATOMIC
InvokeCallback(flag, primary_lock);
}
// Ensure that the lazily initialized fields of *flag have been initialized,
// and return &flag->locks->primary_mu.
absl::Mutex* InitFlagIfNecessary(CommandLineFlag* flag)
LOCK_RETURNED(flag->locks->primary_mu) {
absl::Mutex* mu;
if (!flag->inited.load(std::memory_order_acquire)) {
// Need to initialize lazily initialized fields.
ABSL_CONST_INIT static absl::Mutex init_lock(absl::kConstInit);
init_lock.Lock();
if (flag->locks == nullptr) { // Must initialize Mutexes for this flag.
flag->locks = new flags_internal::CommandLineFlagLocks;
}
mu = &flag->locks->primary_mu;
init_lock.Unlock();
mu->Lock();
if (!flag->retired &&
flag->def == nullptr) { // Need to initialize def and cur fields.
flag->def = (*flag->make_init_value)();
flag->cur = Clone(flag->op, flag->def);
UpdateCopy(flag, mu);
}
mu->Unlock();
flag->inited.store(true, std::memory_order_release);
} else { // All fields initialized; flag->locks is therefore safe to read.
mu = &flag->locks->primary_mu;
}
return mu;
}
// Return true iff flag value was changed via direct-access.
bool ChangedDirectly(CommandLineFlag* flag, const void* a, const void* b) {
if (!flag->IsAbseilFlag()) {
// Need to compare values for direct-access flags.
#define CHANGED_FOR_TYPE(T) \
if (flag->IsOfType<T>()) { \
return *reinterpret_cast<const T*>(a) != *reinterpret_cast<const T*>(b); \
}
CHANGED_FOR_TYPE(bool);
CHANGED_FOR_TYPE(int32_t);
CHANGED_FOR_TYPE(int64_t);
CHANGED_FOR_TYPE(uint64_t);
CHANGED_FOR_TYPE(double);
CHANGED_FOR_TYPE(std::string);
#undef CHANGED_FOR_TYPE
}
return false;
}
// Direct-access flags can be modified without going through the
// flag API. Detect such changes and updated the modified bit.
void UpdateModifiedBit(CommandLineFlag* flag) {
if (!flag->IsAbseilFlag()) {
absl::MutexLock l(InitFlagIfNecessary(flag));
if (!flag->modified && ChangedDirectly(flag, flag->cur, flag->def)) {
flag->modified = true;
}
}
}
bool Validate(CommandLineFlag*, const void*) {
return true;
}
std::string HelpText::GetHelpText() const {
if (help_function_) return help_function_();
if (help_message_) return help_message_;
return {};
}
const int64_t CommandLineFlag::kAtomicInit;
void CommandLineFlag::Read(void* dst,
const flags_internal::FlagOpFn dst_op) const {
absl::ReaderMutexLock l(
InitFlagIfNecessary(const_cast<CommandLineFlag*>(this)));
// `dst_op` is the unmarshaling operation corresponding to the declaration
// visibile at the call site. `op` is the Flag's defined unmarshalling
// operation. They must match for this operation to be well-defined.
if (ABSL_PREDICT_FALSE(dst_op != op)) {
ABSL_INTERNAL_LOG(
ERROR,
absl::StrCat("Flag '", name,
"' is defined as one type and declared as another"));
}
CopyConstruct(op, cur, dst);
}
void CommandLineFlag::Write(const void* src,
const flags_internal::FlagOpFn src_op) {
absl::Mutex* mu = InitFlagIfNecessary(this);
absl::MutexLock l(mu);
// `src_op` is the marshalling operation corresponding to the declaration
// visible at the call site. `op` is the Flag's defined marshalling operation.
// They must match for this operation to be well-defined.
if (ABSL_PREDICT_FALSE(src_op != op)) {
ABSL_INTERNAL_LOG(
ERROR,
absl::StrCat("Flag '", name,
"' is defined as one type and declared as another"));
}
if (ShouldValidateFlagValue(*this)) {
void* obj = Clone(op, src);
std::string ignored_error;
std::string src_as_str = Unparse(marshalling_op, src);
if (!Parse(marshalling_op, src_as_str, obj, &ignored_error) ||
!Validate(this, obj)) {
ABSL_INTERNAL_LOG(ERROR, absl::StrCat("Attempt to set flag '", name,
"' to invalid value ", src_as_str));
}
Delete(op, obj);
}
modified = true;
counter++;
Copy(op, src, cur);
UpdateCopy(this, mu);
}
absl::string_view CommandLineFlag::Typename() const {
// We do not store/report type in Abseil Flags, so that user do not rely on in
// at runtime
if (IsAbseilFlag() || IsRetired()) return "";
#define HANDLE_V1_BUILTIN_TYPE(t) \
if (IsOfType<t>()) { \
return #t; \
}
HANDLE_V1_BUILTIN_TYPE(bool);
HANDLE_V1_BUILTIN_TYPE(int32_t);
HANDLE_V1_BUILTIN_TYPE(int64_t);
HANDLE_V1_BUILTIN_TYPE(uint64_t);
HANDLE_V1_BUILTIN_TYPE(double);
#undef HANDLE_V1_BUILTIN_TYPE
if (IsOfType<std::string>()) {
return "string";
}
return "";
}
std::string CommandLineFlag::Filename() const {
return flags_internal::GetUsageConfig().normalize_filename(this->filename);
}
std::string CommandLineFlag::DefaultValue() const {
return Unparse(this->marshalling_op, this->def);
}
std::string CommandLineFlag::CurrentValue() const {
return Unparse(this->marshalling_op, this->cur);
}
void CommandLineFlag::SetCallback(
const flags_internal::FlagCallback mutation_callback) {
absl::Mutex* mu = InitFlagIfNecessary(this);
absl::MutexLock l(mu);
callback = mutation_callback;
InvokeCallback(this, mu);
}
// Attempts to parse supplied `value` string using parsing routine in the `flag`
// argument. If parsing is successful, it will try to validate that the parsed
// value is valid for the specified 'flag'. Finally 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'
static bool TryParseLocked(CommandLineFlag* flag, void* dst,
absl::string_view value, std::string* err) {
void* tentative_value = Clone(flag->op, flag->def);
std::string parse_err;
if (!Parse(flag->marshalling_op, value, tentative_value, &parse_err)) {
auto type_name = flag->Typename();
absl::string_view err_sep = parse_err.empty() ? "" : "; ";
absl::string_view typename_sep = type_name.empty() ? "" : " ";
*err = absl::StrCat("Illegal value '", value, "' specified for",
typename_sep, type_name, " flag '", flag->Name(), "'",
err_sep, parse_err);
Delete(flag->op, tentative_value);
return false;
}
if (!Validate(flag, tentative_value)) {
*err = absl::StrCat("Failed validation of new value '",
Unparse(flag->marshalling_op, tentative_value),
"' for flag '", flag->Name(), "'");
Delete(flag->op, tentative_value);
return false;
}
flag->counter++;
Copy(flag->op, tentative_value, dst);
Delete(flag->op, tentative_value);
return true;
}
// 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 CommandLineFlag::SetFromString(absl::string_view value,
FlagSettingMode set_mode,
ValueSource source, std::string* err) {
if (IsRetired()) return false;
UpdateModifiedBit(this);
absl::Mutex* mu = InitFlagIfNecessary(this);
absl::MutexLock l(mu);
switch (set_mode) {
case SET_FLAGS_VALUE: {
// set or modify the flag's value
if (!TryParseLocked(this, this->cur, value, err)) return false;
this->modified = true;
UpdateCopy(this, mu);
if (source == kCommandLine) {
this->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 (!this->modified) {
if (!TryParseLocked(this, this->cur, value, err)) return false;
this->modified = true;
UpdateCopy(this, mu);
} else {
// 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(this->Name(), " is already set to ",
// CurrentValue(), "\n");
// return false;
return true;
}
break;
}
case SET_FLAGS_DEFAULT: {
// modify the flag's default-value
if (!TryParseLocked(this, this->def, value, err)) return false;
if (!this->modified) {
// Need to set both defvalue *and* current, in this case
Copy(this->op, this->def, this->cur);
UpdateCopy(this, mu);
}
break;
}
default: {
// unknown set_mode
assert(false);
return false;
}
}
return true;
}
} // namespace flags_internal
} // namespace absl