diff options
Diffstat (limited to 'absl/flags/internal/commandlineflag.cc')
| -rw-r--r-- | absl/flags/internal/commandlineflag.cc | 496 |
1 files changed, 496 insertions, 0 deletions
diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/internal/commandlineflag.cc new file mode 100644 index 00000000..f964165e --- /dev/null +++ b/absl/flags/internal/commandlineflag.cc @@ -0,0 +1,496 @@ +// +// 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 { +inline namespace lts_2019_08_08 { +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 { + +// 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 + +absl::Mutex* InitFlag(CommandLineFlag* flag) { + ABSL_CONST_INIT static absl::Mutex init_lock(absl::kConstInit); + absl::Mutex* mu; + + { + absl::MutexLock lock(&init_lock); + + if (flag->locks == nullptr) { // Must initialize Mutexes for this flag. + flag->locks = new flags_internal::CommandLineFlagLocks; + } + + mu = &flag->locks->primary_mu; + } + + { + absl::MutexLock lock(mu); + + 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); + flag->inited.store(true, std::memory_order_release); + flag->InvokeCallback(); + } + } + + flag->inited.store(true, std::memory_order_release); + return mu; +} + +// Ensure that the lazily initialized fields of *flag have been initialized, +// and return &flag->locks->primary_mu. +absl::Mutex* CommandLineFlag::InitFlagIfNecessary() const + LOCK_RETURNED(locks->primary_mu) { + if (!this->inited.load(std::memory_order_acquire)) { + return InitFlag(const_cast<CommandLineFlag*>(this)); + } + + // All fields initialized; this->locks is therefore safe to read. + return &this->locks->primary_mu; +} + +void CommandLineFlag::Destroy() const { + // Values are heap allocated for retired and Abseil Flags. + if (IsRetired() || IsAbseilFlag()) { + if (this->cur) Delete(this->op, this->cur); + if (this->def) Delete(this->op, this->def); + } + + delete this->locks; +} + +bool CommandLineFlag::IsModified() const { + absl::MutexLock l(InitFlagIfNecessary()); + return modified; +} + +void CommandLineFlag::SetModified(bool is_modified) { + absl::MutexLock l(InitFlagIfNecessary()); + modified = is_modified; +} + +bool CommandLineFlag::IsSpecifiedOnCommandLine() const { + absl::MutexLock l(InitFlagIfNecessary()); + return on_command_line; +} + +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 { + absl::MutexLock l(InitFlagIfNecessary()); + + return Unparse(this->marshalling_op, this->def); +} + +std::string CommandLineFlag::CurrentValue() const { + absl::MutexLock l(InitFlagIfNecessary()); + + return Unparse(this->marshalling_op, this->cur); +} + +bool CommandLineFlag::HasValidatorFn() const { + absl::MutexLock l(InitFlagIfNecessary()); + + return this->validator != nullptr; +} + +bool CommandLineFlag::SetValidatorFn(FlagValidator fn) { + absl::MutexLock l(InitFlagIfNecessary()); + + // ok to register the same function over and over again + if (fn == this->validator) return true; + + // Can't set validator to a different function, unless reset first. + if (fn != nullptr && this->validator != nullptr) { + ABSL_INTERNAL_LOG( + WARNING, absl::StrCat("Ignoring SetValidatorFn() for flag '", Name(), + "': validate-fn already registered")); + + return false; + } + + this->validator = fn; + return true; +} + +bool CommandLineFlag::InvokeValidator(const void* value) const + EXCLUSIVE_LOCKS_REQUIRED(this->locks->primary_mu) { + if (!this->validator) { + return true; + } + + (void)value; + + ABSL_INTERNAL_LOG( + FATAL, + absl::StrCat("Flag '", Name(), + "' of encapsulated type should not have a validator")); + + return false; +} + +void CommandLineFlag::SetCallback( + const flags_internal::FlagCallback mutation_callback) { + absl::MutexLock l(InitFlagIfNecessary()); + + callback = mutation_callback; + + InvokeCallback(); +} + +// 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 CommandLineFlag::InvokeCallback() + EXCLUSIVE_LOCKS_REQUIRED(this->locks->primary_mu) { + if (!this->callback) return; + + // The callback lock is guaranteed initialized, because *locks->primary_mu + // exists. + absl::Mutex* callback_mu = &this->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. + this->locks->primary_mu.Unlock(); + + { + absl::MutexLock lock(callback_mu); + this->callback(); + } + + this->locks->primary_mu.Lock(); +} + +// 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' +bool TryParseLocked(CommandLineFlag* flag, void* dst, absl::string_view value, + std::string* err) + EXCLUSIVE_LOCKS_REQUIRED(flag->locks->primary_mu) { + 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 (!flag->InvokeValidator(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; + + absl::MutexLock l(InitFlagIfNecessary()); + + // Direct-access flags can be modified without going through the + // flag API. Detect such changes and update the flag->modified bit. + if (!IsAbseilFlag()) { + if (!this->modified && ChangedDirectly(this, this->cur, this->def)) { + this->modified = true; + } + } + + 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); + InvokeCallback(); + + 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); + InvokeCallback(); + } 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); + InvokeCallback(); + } + break; + } + default: { + // unknown set_mode + assert(false); + return false; + } + } + + return true; +} + +void CommandLineFlag::StoreAtomic(size_t size) { + int64_t t = 0; + assert(size <= sizeof(int64_t)); + memcpy(&t, this->cur, size); + this->atomic.store(t, std::memory_order_release); +} + +void CommandLineFlag::CheckDefaultValueParsingRoundtrip() const { + std::string v = DefaultValue(); + + absl::MutexLock lock(InitFlagIfNecessary()); + + void* dst = Clone(this->op, this->def); + std::string error; + if (!flags_internal::Parse(this->marshalling_op, v, dst, &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. + Delete(this->op, dst); +} + +bool CommandLineFlag::ValidateDefaultValue() const { + absl::MutexLock lock(InitFlagIfNecessary()); + return InvokeValidator(this->def); +} + +bool CommandLineFlag::ValidateInputValue(absl::string_view value) const { + absl::MutexLock l(InitFlagIfNecessary()); // protect default value access + + void* obj = Clone(this->op, this->def); + std::string ignored_error; + const bool result = + flags_internal::Parse(this->marshalling_op, value, obj, &ignored_error) && + InvokeValidator(obj); + Delete(this->op, obj); + return result; +} + +const int64_t CommandLineFlag::kAtomicInit; + +void CommandLineFlag::Read(void* dst, + const flags_internal::FlagOpFn dst_op) const { + absl::ReaderMutexLock l(InitFlagIfNecessary()); + + // `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::MutexLock l(InitFlagIfNecessary()); + + // `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) || + !InvokeValidator(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); + InvokeCallback(); +} + +std::string HelpText::GetHelpText() const { + if (help_function_) return help_function_(); + if (help_message_) return help_message_; + + return {}; +} + +// 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) { +#define STORE_ATOMIC(T) \ + else if (flag->IsOfType<T>()) { \ + flag->StoreAtomic(sizeof(T)); \ + } + + if (false) { + } + ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(STORE_ATOMIC) +#undef STORE_ATOMIC +} + +// 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; +} + +} // namespace flags_internal +} // inline namespace lts_2019_08_08 +} // namespace absl |