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rocksdb/options/options_parser.h
Josh Kang 4b983da055 Spell out special member functions (rule of five) (#15387)
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/15387

## Summary

RocksDB's `.clang-tidy` enables `cppcoreguidelines-special-member-functions`,
`cppcoreguidelines-virtual-class-destructor` and the noexcept-move checks,
and clang warns `-Wdeprecated-copy-with-user-provided-dtor`. A full scan
reports 476 findings. In most of them, a class declares a destructor (or
copy operations) but leaves the rest of copy/move implicit. That has two
costs. Readers can't tell whether a class may be copied or moved. And
resource-owning classes keep an implicit copy that would double-free if
anyone ever used it. This diff resolves 453 of the 476.

Approach, picked per class from least to most invasive:
1. An empty user-provided destructor becomes `= default`. This covers most
   interface classes, such as `virtual ~X() {}` -> `= default`. If the
   class is still copied, that would only rename the deprecated-copy
   warning, so the destructor is removed instead when nothing needs it
   (`Customizable`, `TableFactory` and `InternalKeyComparator` inherit a
   virtual one; `IteratorWrapperBase` isn't polymorphic), and
   `MemTableRep::KeyComparator` gets defaulted copy and move.
2. Classes whose copy is already deleted get explicitly deleted move
   operations too. Move was already unavailable, so this only documents
   it.
3. Resource-owning classes that are never copied get deleted copy and move
   operations. Examples: the C API wrapper structs, which run a
   `destructor_` callback (edited in `tools/c_api_gen/c_base.cc` and
   regenerated into `db/c.cc`); `ShardedCache`, which frees its shards;
   iterator wrappers; and RAII handles.
4. Value types that are copied or moved get the missing operations as
   `= default`, which keeps their current behavior.
5. Exception specifications of existing functions are unchanged, except
   for `WriteBatch`'s move assignment (below): no other `noexcept` is
   added or removed. Only the move operations this diff
   newly declares (`Comparator`, `FileSampledStats` and the thread-local
   `Entry`) are `noexcept`; they copy only scalars or atomics.

`WriteBatch`'s copy and move assignment destroyed `*this` and
placement-new'ed a new `WriteBatch` over it. That is undefined behavior
when `*this` is a subclass, and if the copy constructor threw, `*this`
was left destroyed and was later destroyed again. Move assignment now
assigns member-wise and ends in the same state as the move constructor,
which leaves `has_key_with_ts_`, the timestamp-size tracking and the
other fields it doesn't copy at their defaults. `rep_` is swapped through
a temporary, because a plain string move-assignment can keep the old
buffer (e.g. a large batch reset with `batch = WriteBatch()` would keep
its memory). Nothing in it can throw, so it is now `noexcept`. Copy
assignment copies into a temporary and moves it in, so a throwing copy
leaves `*this` unchanged.

Bugs this exposed and fixed:
- `RestoreAfterCopyOrCreateWorkItem` (backup engine): the hand-written
  move constructor and assignment moved only some fields, so `from_file`
  and `to_file` were empty after `push_back(std::move(...))`. A restore
  that hit a checksum mismatch then reported "While restoring  -> : ..."
  without file names. It now uses the compiler-generated moves, which
  are still `noexcept`.
- `ExternalSstFileIngestionJob` lived in a `std::vector`, and its
  destructor frees raw-owned pointers, so the implicit copy used on
  vector reallocation would double-free. Its file batches also point into
  its own inline file storage, so neither a copy nor a move is safe after
  `Prepare()`. Copy and move are now deleted, and `DBImpl` holds jobs
  through `std::unique_ptr`.

Compatibility: no public class loses an operation users can call. Public
interfaces mostly only get `virtual ~X() = default;`.
`WriteBatch`'s move assignment becomes `noexcept`, which is not part of
the mangled name, so the ABI doesn't change.
`SubcompactionJobInfo` and `CompactionJobInfo` intentionally stay C++20
aggregates, so users' aggregate and designated initializers keep
compiling. `Configurable`, `CompareInterface`, `WriteBatchBase`,
`ObjectLibrary::Entry` and `MemTableRep::KeyComparator` declare defaulted
copy and move, and `Customizable` no longer declares a destructor. As a
result, `Configurable` and `Customizable` subclasses that declare no
destructor or copy operations of their own now move their
registered-options list instead of copying it. In-tree, these are the
mutable-options adapters, the table factories, the memory allocators and
test classes; all are held through smart pointers or used in place, and
`Clone()` copies, so none is moved by value.

Not changed (23): `IODebugContext` (custom deep copy plus a
`std::shared_mutex`), `DBWithColumnFamilies` in db_bench (stored in a
`std::vector` with non-movable members), `Snapshot`'s protected virtual
destructor (intended), `ManagedSnapshot`, the `SubcompactionJobInfo` and
`CompactionJobInfo` aggregates, and the 16 noexcept-move-constructor and
noexcept-swap findings on existing functions, including `autovector`'s
move assignment (adding `noexcept` would change their exception
specifications). Copying `ManagedSnapshot` already double-releases the
snapshot. Fixing that needs a real move implementation and is a behavior
change, so it is left for a separate diff.

Reviewed By: rban1

Differential Revision: D123186309

fbshipit-source-id: 6f8e57e233e12199a007407130bb9a1f6d52e8d1
2026-10-12 16:00:09 -07:00

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5.8 KiB
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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <map>
#include <string>
#include <unordered_set>
#include <vector>
#include "rocksdb/env.h"
#include "rocksdb/options.h"
namespace ROCKSDB_NAMESPACE {
struct ConfigOptions;
class OptionTypeInfo;
class TableFactory;
#define ROCKSDB_OPTION_FILE_MAJOR 1
#define ROCKSDB_OPTION_FILE_MINOR 1
enum OptionSection : char {
kOptionSectionVersion = 0,
kOptionSectionDBOptions,
kOptionSectionCFOptions,
kOptionSectionTableOptions,
kOptionSectionUnknown
};
static const std::string opt_section_titles[] = {
"Version", "DBOptions", "CFOptions", "TableOptions/", "Unknown"};
Status PersistRocksDBOptions(const WriteOptions& write_options,
const DBOptions& db_opt,
const std::vector<std::string>& cf_names,
const std::vector<ColumnFamilyOptions>& cf_opts,
const std::string& file_name, FileSystem* fs);
Status PersistRocksDBOptions(const WriteOptions& write_options,
const ConfigOptions& config_options,
const DBOptions& db_opt,
const std::vector<std::string>& cf_names,
const std::vector<ColumnFamilyOptions>& cf_opts,
const std::string& file_name, FileSystem* fs);
class RocksDBOptionsParser {
public:
explicit RocksDBOptionsParser();
~RocksDBOptionsParser() = default;
void Reset();
// `file_readahead_size` is used for readahead for the option file.
// If 0 is given, a default value will be used.
Status Parse(const std::string& file_name, FileSystem* fs,
bool ignore_unknown_options, size_t file_readahead_size);
Status Parse(const ConfigOptions& config_options,
const std::string& file_name, FileSystem* fs);
static std::string TrimAndRemoveComment(const std::string& line,
const bool trim_only = false);
const DBOptions* db_opt() const { return &db_opt_; }
const std::unordered_map<std::string, std::string>* db_opt_map() const {
return &db_opt_map_;
}
const std::vector<ColumnFamilyOptions>* cf_opts() const { return &cf_opts_; }
const std::vector<std::string>* cf_names() const { return &cf_names_; }
const std::vector<std::unordered_map<std::string, std::string>>* cf_opt_maps()
const {
return &cf_opt_maps_;
}
const ColumnFamilyOptions* GetCFOptions(const std::string& name) {
return GetCFOptionsImpl(name);
}
size_t NumColumnFamilies() { return cf_opts_.size(); }
static Status VerifyRocksDBOptionsFromFile(
const ConfigOptions& config_options, const DBOptions& db_opt,
const std::vector<std::string>& cf_names,
const std::vector<ColumnFamilyOptions>& cf_opts,
const std::string& file_name, FileSystem* fs);
static Status VerifyRocksDBOptionsFromFile(
const ConfigOptions& config_options, const DBOptions& db_opt,
const std::vector<std::string>& cf_names,
const std::vector<ColumnFamilyOptions>& cf_opts,
const std::unordered_set<std::string>& live_cf_names,
const std::string& file_name, FileSystem* fs);
static Status VerifyDBOptions(
const ConfigOptions& config_options, const DBOptions& base_opt,
const DBOptions& new_opt,
const std::unordered_map<std::string, std::string>* new_opt_map =
nullptr);
static Status VerifyCFOptions(
const ConfigOptions& config_options, const ColumnFamilyOptions& base_opt,
const ColumnFamilyOptions& new_opt,
const std::unordered_map<std::string, std::string>* new_opt_map =
nullptr);
static Status VerifyTableFactory(const ConfigOptions& config_options,
const TableFactory* base_tf,
const TableFactory* file_tf);
static Status ExtraParserCheck(const RocksDBOptionsParser& input_parser);
static Status ParseStatement(std::string* name, std::string* value,
const std::string& line, const int line_num);
protected:
bool IsSection(const std::string& line);
Status ParseSection(OptionSection* section, std::string* title,
std::string* argument, const std::string& line,
const int line_num);
Status CheckSection(const OptionSection section,
const std::string& section_arg, const int line_num);
Status EndSection(
const ConfigOptions& config_options, const OptionSection section,
const std::string& title, const std::string& section_arg,
const std::unordered_map<std::string, std::string>& opt_map);
Status ValidityCheck();
static Status InvalidArgument(const int line_num, const std::string& message);
Status ParseVersionNumber(const std::string& ver_name,
const std::string& ver_string, const int max_count,
int* version);
ColumnFamilyOptions* GetCFOptionsImpl(const std::string& name) {
assert(cf_names_.size() == cf_opts_.size());
for (size_t i = 0; i < cf_names_.size(); ++i) {
if (cf_names_[i] == name) {
return &cf_opts_[i];
}
}
return nullptr;
}
private:
DBOptions db_opt_;
std::unordered_map<std::string, std::string> db_opt_map_;
std::vector<std::string> cf_names_;
std::vector<ColumnFamilyOptions> cf_opts_;
std::vector<std::unordered_map<std::string, std::string>> cf_opt_maps_;
bool has_version_section_;
bool has_db_options_;
bool has_default_cf_options_;
int db_version[3];
int opt_file_version[3];
};
} // namespace ROCKSDB_NAMESPACE