fix compilation with g++ option `-Wsuggest-override` (#4272)

Summary:
Fixes compilation warnings (which are turned into compilation errors by default) when compiling with g++ option `-Wsuggest-override`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4272

Differential Revision: D9322556

Pulled By: siying

fbshipit-source-id: abd57a29ec8f544bee77c0bb438f31be830b7244

db/range_del_aggregator.cc

@@ -50,7 +50,7 @@ class UncollapsedRangeDelMap : public RangeDelMap {
       : rep_(TombstoneStartKeyComparator(ucmp)), ucmp_(ucmp) {}
 
   bool ShouldDelete(const ParsedInternalKey& parsed,
-                    RangeDelPositioningMode mode) {
+                    RangeDelPositioningMode mode) override {
     (void)mode;
     assert(mode == RangeDelPositioningMode::kFullScan);
     for (const auto& tombstone : rep_) {
@@ -65,7 +65,7 @@ class UncollapsedRangeDelMap : public RangeDelMap {
     return false;
   }
 
-  bool IsRangeOverlapped(const Slice& start, const Slice& end) {
+  bool IsRangeOverlapped(const Slice& start, const Slice& end) override {
     for (const auto& tombstone : rep_) {
       if (ucmp_->Compare(start, tombstone.end_key_) < 0 &&
           ucmp_->Compare(tombstone.start_key_, end) <= 0 &&
@@ -76,13 +76,13 @@ class UncollapsedRangeDelMap : public RangeDelMap {
     return false;
   }
 
-  void AddTombstone(RangeTombstone tombstone) { rep_.emplace(tombstone); }
+  void AddTombstone(RangeTombstone tombstone) override { rep_.emplace(tombstone); }
 
-  size_t Size() const { return rep_.size(); }
+  size_t Size() const override { return rep_.size(); }
 
-  void InvalidatePosition() {}  // no-op
+  void InvalidatePosition() override {}  // no-op
 
-  std::unique_ptr<RangeDelIterator> NewIterator() {
+  std::unique_ptr<RangeDelIterator> NewIterator() override {
     return std::unique_ptr<RangeDelIterator>(new Iterator(this->rep_));
   }
 };
@@ -176,7 +176,7 @@ class CollapsedRangeDelMap : public RangeDelMap {
   }
 
   bool ShouldDelete(const ParsedInternalKey& parsed,
-                    RangeDelPositioningMode mode) {
+                    RangeDelPositioningMode mode) override {
     if (iter_ == rep_.end() &&
         (mode == RangeDelPositioningMode::kForwardTraversal ||
          mode == RangeDelPositioningMode::kBackwardTraversal)) {
@@ -227,14 +227,14 @@ class CollapsedRangeDelMap : public RangeDelMap {
     return parsed.sequence < iter_->second;
   }
 
-  bool IsRangeOverlapped(const Slice&, const Slice&) {
+  bool IsRangeOverlapped(const Slice&, const Slice&) override {
     // Unimplemented because the only client of this method, file ingestion,
     // uses uncollapsed maps.
     fprintf(stderr, "CollapsedRangeDelMap::IsRangeOverlapped unimplemented");
     abort();
   }
 
-  void AddTombstone(RangeTombstone t) {
+  void AddTombstone(RangeTombstone t) override {
     if (ucmp_->Compare(t.start_key_, t.end_key_) >= 0 || t.seq_ == 0) {
       // The tombstone covers no keys. Nothing to do.
       return;
@@ -344,11 +344,11 @@ class CollapsedRangeDelMap : public RangeDelMap {
     }
   }
 
-  size_t Size() const { return rep_.size() - 1; }
+  size_t Size() const override { return rep_.size() - 1; }
 
-  void InvalidatePosition() { iter_ = rep_.end(); }
+  void InvalidatePosition() override { iter_ = rep_.end(); }
 
-  std::unique_ptr<RangeDelIterator> NewIterator() {
+  std::unique_ptr<RangeDelIterator> NewIterator() override {
     return std::unique_ptr<RangeDelIterator>(new Iterator(this->rep_));
   }
 };

db/snapshot_checker.h

@@ -20,7 +20,7 @@ class DisableGCSnapshotChecker : public SnapshotChecker {
  public:
   virtual ~DisableGCSnapshotChecker() {}
   virtual bool IsInSnapshot(SequenceNumber /*sequence*/,
-                            SequenceNumber /*snapshot_sequence*/) const {
+                            SequenceNumber /*snapshot_sequence*/) const override {
     // By returning false, we prevent all the values from being GCed
     return false;
   }

util/testutil.h

@@ -247,7 +247,7 @@ class RandomRWStringSink : public RandomRWFile {
  public:
   explicit RandomRWStringSink(StringSink* ss) : ss_(ss) {}
 
-  Status Write(uint64_t offset, const Slice& data) {
+  Status Write(uint64_t offset, const Slice& data) override {
     if (offset + data.size() > ss_->contents_.size()) {
       ss_->contents_.resize(offset + data.size(), '\0');
     }
@@ -258,7 +258,7 @@ class RandomRWStringSink : public RandomRWFile {
   }
 
   Status Read(uint64_t offset, size_t n, Slice* result,
-              char* /*scratch*/) const {
+              char* /*scratch*/) const override {
     *result = Slice(nullptr, 0);
     if (offset < ss_->contents_.size()) {
       size_t str_res_sz =
@@ -268,11 +268,11 @@ class RandomRWStringSink : public RandomRWFile {
     return Status::OK();
   }
 
-  Status Flush() { return Status::OK(); }
+  Status Flush() override { return Status::OK(); }
 
-  Status Sync() { return Status::OK(); }
+  Status Sync() override { return Status::OK(); }
 
-  Status Close() { return Status::OK(); }
+  Status Close() override { return Status::OK(); }
 
   const std::string& contents() const { return ss_->contents(); }
 

utilities/env_mirror.cc

@@ -20,7 +20,7 @@ class SequentialFileMirror : public SequentialFile {
   std::string fname;
   explicit SequentialFileMirror(std::string f) : fname(f) {}
 
-  Status Read(size_t n, Slice* result, char* scratch) {
+  Status Read(size_t n, Slice* result, char* scratch) override {
     Slice aslice;
     Status as = a_->Read(n, &aslice, scratch);
     if (as == Status::OK()) {
@@ -44,13 +44,13 @@ class SequentialFileMirror : public SequentialFile {
     return as;
   }
 
-  Status Skip(uint64_t n) {
+  Status Skip(uint64_t n) override {
     Status as = a_->Skip(n);
     Status bs = b_->Skip(n);
     assert(as == bs);
     return as;
   }
-  Status InvalidateCache(size_t offset, size_t length) {
+  Status InvalidateCache(size_t offset, size_t length) override {
     Status as = a_->InvalidateCache(offset, length);
     Status bs = b_->InvalidateCache(offset, length);
     assert(as == bs);
@@ -64,7 +64,7 @@ class RandomAccessFileMirror : public RandomAccessFile {
   std::string fname;
   explicit RandomAccessFileMirror(std::string f) : fname(f) {}
 
-  Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const {
+  Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const override {
     Status as = a_->Read(offset, n, result, scratch);
     if (as == Status::OK()) {
       char* bscratch = new char[n];
@@ -86,7 +86,7 @@ class RandomAccessFileMirror : public RandomAccessFile {
     return as;
   }
 
-  size_t GetUniqueId(char* id, size_t max_size) const {
+  size_t GetUniqueId(char* id, size_t max_size) const override {
     // NOTE: not verified
     return a_->GetUniqueId(id, max_size);
   }

utilities/persistent_cache/persistent_cache_tier.h

@@ -251,20 +251,20 @@ class PersistentCacheTier : public PersistentCache {
   // Print stats to string recursively
   virtual std::string PrintStats();
 
-  virtual PersistentCache::StatsType Stats();
+  virtual PersistentCache::StatsType Stats() override;
 
   // Insert to page cache
   virtual Status Insert(const Slice& page_key, const char* data,
-                        const size_t size) = 0;
+                        const size_t size) override = 0;
 
   // Lookup page cache by page identifier
   virtual Status Lookup(const Slice& page_key, std::unique_ptr<char[]>* data,
-                        size_t* size) = 0;
+                        size_t* size) override = 0;
 
   // Does it store compressed data ?
-  virtual bool IsCompressed() = 0;
+  virtual bool IsCompressed() override = 0;
 
-  virtual std::string GetPrintableOptions() const = 0;
+  virtual std::string GetPrintableOptions() const override = 0;
 
   // Return a reference to next tier
   virtual Tier& next_tier() { return next_tier_; }