Make clang-analyzer happy (#5821)

Summary:
clang-analyzer has uncovered a bunch of places where the code is relying
on pointers being valid and one case (in VectorIterator) where a moved-from
object is being used:

In file included from db/range_tombstone_fragmenter.cc:17:
./util/vector_iterator.h:23:18: warning: Method called on moved-from object 'keys' of type 'std::vector'
        current_(keys.size()) {
                 ^~~~~~~~~~~
1 warning generated.
utilities/persistent_cache/block_cache_tier_file.cc:39:14: warning: Called C++ object pointer is null
  Status s = env->NewRandomAccessFile(filepath, file, opt);
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:47:19: warning: Called C++ object pointer is null
  Status status = env_->GetFileSize(Path(), size);
                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:290:14: warning: Called C++ object pointer is null
  Status s = env_->FileExists(Path());
             ^~~~~~~~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:363:35: warning: Called C++ object pointer is null
    CacheWriteBuffer* const buf = alloc_->Allocate();
                                  ^~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:399:41: warning: Called C++ object pointer is null
  const uint64_t file_off = buf_doff_ * alloc_->BufferSize();
                                        ^~~~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:463:33: warning: Called C++ object pointer is null
  size_t start_idx = lba.off_ / alloc_->BufferSize();
                                ^~~~~~~~~~~~~~~~~~~~
utilities/persistent_cache/block_cache_tier_file.cc:515:5: warning: Called C++ object pointer is null
    alloc_->Deallocate(bufs_[i]);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
7 warnings generated.
ar: creating librocksdb_debug.a
utilities/memory/memory_test.cc:68:25: warning: Called C++ object pointer is null
      cache_set->insert(db->GetDBOptions().row_cache.get());
                        ^~~~~~~~~~~~~~~~~~
1 warning generated.

The patch fixes these by adding assertions and explicitly passing in zero
when initializing VectorIterator::current_ (which preserves the existing
behavior).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5821

Test Plan: Ran make check and make analyze to make sure the warnings have disappeared.

Differential Revision: D17455949

Pulled By: ltamasi

fbshipit-source-id: 363619618ea649a0674287f9f3b3393e390571ee

util/vector_iterator.h

@@ -20,7 +20,7 @@ class VectorIterator : public InternalIterator {
       : keys_(std::move(keys)),
         values_(std::move(values)),
         indexed_cmp_(icmp, &keys_),
-        current_(keys.size()) {
+        current_(0) {
     assert(keys_.size() == values_.size());
 
     indices_.reserve(keys_.size());

utilities/memory/memory_test.cc

@@ -57,6 +57,8 @@ class MemoryTest : public testing::Test {
     cache_set->clear();
 
     for (auto* db : dbs) {
+      assert(db);
+
       // Cache from DBImpl
       StackableDB* sdb = dynamic_cast<StackableDB*>(db);
       DBImpl* db_impl = dynamic_cast<DBImpl*>(sdb ? sdb->GetBaseDB() : db);

utilities/persistent_cache/block_cache_tier_file.cc

@@ -34,6 +34,8 @@ Status NewWritableCacheFile(Env* const env, const std::string& filepath,
 Status NewRandomAccessCacheFile(Env* const env, const std::string& filepath,
                                 std::unique_ptr<RandomAccessFile>* file,
                                 const bool use_direct_reads = true) {
+  assert(env);
+
   EnvOptions opt;
   opt.use_direct_reads = use_direct_reads;
   Status s = env->NewRandomAccessFile(filepath, file, opt);
@@ -44,6 +46,8 @@ Status NewRandomAccessCacheFile(Env* const env, const std::string& filepath,
 // BlockCacheFile
 //
 Status BlockCacheFile::Delete(uint64_t* size) {
+  assert(env_);
+
   Status status = env_->GetFileSize(Path(), size);
   if (!status.ok()) {
     return status;
@@ -287,6 +291,8 @@ bool WriteableCacheFile::Create(const bool /*enable_direct_writes*/,
   ROCKS_LOG_DEBUG(log_, "Creating new cache %s (max size is %d B)",
                   Path().c_str(), max_size_);
 
+  assert(env_);
+
   Status s = env_->FileExists(Path());
   if (s.ok()) {
     ROCKS_LOG_WARN(log_, "File %s already exists. %s", Path().c_str(),
@@ -359,6 +365,8 @@ bool WriteableCacheFile::ExpandBuffer(const size_t size) {
 
   // expand the buffer until there is enough space to write `size` bytes
   assert(free < size);
+  assert(alloc_);
+
   while (free < size) {
     CacheWriteBuffer* const buf = alloc_->Allocate();
     if (!buf) {
@@ -394,6 +402,7 @@ void WriteableCacheFile::DispatchBuffer() {
   assert(eof_ || buf_doff_ < buf_woff_);
   assert(buf_doff_ < bufs_.size());
   assert(file_);
+  assert(alloc_);
 
   auto* buf = bufs_[buf_doff_];
   const uint64_t file_off = buf_doff_ * alloc_->BufferSize();
@@ -453,6 +462,7 @@ bool WriteableCacheFile::ReadBuffer(const LBA& lba, char* data) {
   rwlock_.AssertHeld();
 
   assert(lba.off_ < disk_woff_);
+  assert(alloc_);
 
   // we read from the buffers like reading from a flat file. The list of buffers
   // are treated as contiguous stream of data
@@ -511,6 +521,8 @@ void WriteableCacheFile::Close() {
 }
 
 void WriteableCacheFile::ClearBuffers() {
+  assert(alloc_);
+
   for (size_t i = 0; i < bufs_.size(); ++i) {
     alloc_->Deallocate(bufs_[i]);
   }