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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
168 lines
6.4 KiB
C++
168 lines
6.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <string>
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#include <vector>
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#include "db/db_impl/db_impl.h"
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namespace ROCKSDB_NAMESPACE {
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// TODO: Share common structure with DBImplSecondary and DBImplReadOnly
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class CompactedDBImpl : public DBImpl {
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public:
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CompactedDBImpl(const DBOptions& options, const std::string& dbname);
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// No copying allowed
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CompactedDBImpl(const CompactedDBImpl&) = delete;
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void operator=(const CompactedDBImpl&) = delete;
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CompactedDBImpl(CompactedDBImpl&&) = delete;
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void operator=(CompactedDBImpl&&) = delete;
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~CompactedDBImpl() override;
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static Status Open(const Options& options, const std::string& dbname,
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std::unique_ptr<DB>* dbptr);
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// Implementations of the DB interface
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using DB::Get;
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DECLARE_SYNC_AND_ASYNC_OVERRIDE(Status, Get, const ReadOptions& options,
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ColumnFamilyHandle* column_family,
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const Slice& key, PinnableSlice* value,
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std::string* timestamp);
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using DB::GetWithMetadata;
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Status GetWithMetadata(const ReadOptions& options,
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ColumnFamilyHandle* column_family, const Slice& key,
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PinnableSlice* value,
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OutputMetadata* output_metadata) override;
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using DB::MultiGet;
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// Note that CompactedDBImpl::MultiGet is not the optimized version of
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// MultiGet to use.
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// TODO: optimize CompactedDBImpl::MultiGet, see DBImpl::MultiGet for details.
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DECLARE_SYNC_AND_ASYNC_OVERRIDE(void, MultiGet, const ReadOptions& options,
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size_t num_keys,
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ColumnFamilyHandle** column_families,
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const Slice* keys, PinnableSlice* values,
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std::string* timestamps, Status* statuses,
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const bool sorted_input);
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using DB::MultiGetWithMetadata;
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void MultiGetWithMetadata(const ReadOptions& options, size_t num_keys,
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ColumnFamilyHandle* const* column_families,
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const Slice* keys, PinnableSlice* values,
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Status* statuses,
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MultiGetOutputMetadata* output_metadata,
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const bool sorted_input) override;
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using DBImpl::Put;
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Status Put(const WriteOptions& /*options*/,
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ColumnFamilyHandle* /*column_family*/, const Slice& /*key*/,
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const Slice& /*value*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DBImpl::PutEntity;
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Status PutEntity(const WriteOptions& /* options */,
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ColumnFamilyHandle* /* column_family */,
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const Slice& /* key */,
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const WideColumns& /* columns */) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DBImpl::Merge;
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Status Merge(const WriteOptions& /*options*/,
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ColumnFamilyHandle* /*column_family*/, const Slice& /*key*/,
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const Slice& /*value*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DBImpl::Delete;
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Status Delete(const WriteOptions& /*options*/,
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ColumnFamilyHandle* /*column_family*/,
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const Slice& /*key*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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Status Write(const WriteOptions& /*options*/,
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WriteBatch* /*updates*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DBImpl::CompactRange;
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Status CompactRange(const CompactRangeOptions& /*options*/,
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ColumnFamilyHandle* /*column_family*/,
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const Slice* /*begin*/, const Slice* /*end*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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Status DisableFileDeletions() override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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Status EnableFileDeletions() override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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Status GetLiveFiles(std::vector<std::string>& ret,
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uint64_t* manifest_file_size,
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bool /*flush_memtable*/) override {
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return DBImpl::GetLiveFiles(ret, manifest_file_size,
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false /* flush_memtable */);
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}
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using DBImpl::Flush;
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Status Flush(const FlushOptions& /*options*/,
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ColumnFamilyHandle* /*column_family*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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Status SyncWAL() override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DB::IngestExternalFile;
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Status IngestExternalFile(
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ColumnFamilyHandle* /*column_family*/,
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const std::vector<std::string>& /*external_files*/,
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const IngestExternalFileOptions& /*ingestion_options*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DB::CreateColumnFamilyWithImport;
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Status CreateColumnFamilyWithImport(
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const ColumnFamilyOptions& /*options*/,
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const std::string& /*column_family_name*/,
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const ImportColumnFamilyOptions& /*import_options*/,
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const std::vector<const ExportImportFilesMetaData*>& /*metadatas*/,
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ColumnFamilyHandle** /*handle*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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using DB::ClipColumnFamily;
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Status ClipColumnFamily(ColumnFamilyHandle* /*column_family*/,
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const Slice& /*begin*/,
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const Slice& /*end*/) override {
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return Status::NotSupported("Not supported in compacted db mode.");
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}
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// FIXME: some missing overrides for more "write" functions
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// Share with DBImplReadOnly?
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protected:
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Status FlushForGetLiveFiles(bool /*force_atomic_flush*/) override {
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// No-op for read-only DB
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return Status::OK();
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}
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private:
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friend class DB;
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inline size_t FindFile(const Slice& key);
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Status Init(const Options& options);
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ColumnFamilyData* cfd_;
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Version* version_;
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const Comparator* user_comparator_;
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LevelFilesBrief files_;
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int files_level_{0};
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};
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} // namespace ROCKSDB_NAMESPACE
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