util: Fix coverity issues

Summary:
util/concurrent_arena.h:
CID 1396145 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
2. uninit_member: Non-static class member free_begin_ is not initialized in this constructor nor in any functions that it calls.
 94    Shard() : allocated_and_unused_(0) {}

util/dynamic_bloom.cc:
	1. Condition hash_func == NULL, taking true branch.

CID 1322821 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
3. uninit_member: Non-static class member data_ is not initialized in this constructor nor in any functions that it calls.
47      hash_func_(hash_func == nullptr ? &BloomHash : hash_func) {}
48

util/file_reader_writer.h:
204 private:
205  AlignedBuffer buffer_;
   	member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize buffer_offset_.
206  uint64_t buffer_offset_;

CID 1418246 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize buffer_len_.
207  size_t buffer_len_;
208};

util/thread_local.cc:
341#endif

CID 1322795 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
3. uninit_member: Non-static class member pthread_key_ is not initialized in this constructor nor in any functions that it calls.
342}

40struct ThreadData {
   	2. uninit_member: Non-static class member next is not initialized in this constructor nor in any functions that it calls.

CID 1400668 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
4. uninit_member: Non-static class member prev is not initialized in this constructor nor in any functions that it calls.
 41  explicit ThreadData(ThreadLocalPtr::StaticMeta* _inst) : entries(), inst(_inst) {}
 42  std::vector<Entry> entries;
   	1. member_decl: Class member declaration for next.
 43  ThreadData* next;
   	3. member_decl: Class member declaration for prev.
 44  ThreadData* prev;
 45  ThreadLocalPtr::StaticMeta* inst;
 46};
Closes https://github.com/facebook/rocksdb/pull/3123

Differential Revision: D6233566

Pulled By: sagar0

fbshipit-source-id: aa2068790ea69787a0035c0db39d59b0c25108db

util/concurrent_arena.h

@@ -91,7 +91,7 @@ class ConcurrentArena : public Allocator {
     char* free_begin_;
     std::atomic<size_t> allocated_and_unused_;
 
-    Shard() : allocated_and_unused_(0) {}
+    Shard() : free_begin_(nullptr), allocated_and_unused_(0) {}
   };
 
 #ifdef ROCKSDB_SUPPORT_THREAD_LOCAL

util/dynamic_bloom.cc

@@ -44,7 +44,8 @@ DynamicBloom::DynamicBloom(uint32_t num_probes,
     : kTotalBits(0),
       kNumBlocks(0),
       kNumProbes(num_probes),
-      hash_func_(hash_func == nullptr ? &BloomHash : hash_func) {}
+      hash_func_(hash_func == nullptr ? &BloomHash : hash_func),
+      data_(0) {}
 
 void DynamicBloom::SetRawData(unsigned char* raw_data, uint32_t total_bits,
                               uint32_t num_blocks) {

util/file_reader_writer.h

@@ -201,6 +201,7 @@ class WritableFileWriter {
 
 class FilePrefetchBuffer {
  public:
+  FilePrefetchBuffer() : buffer_offset_(0), buffer_len_(0) {}
   Status Prefetch(RandomAccessFileReader* reader, uint64_t offset, size_t n);
   bool TryReadFromCache(uint64_t offset, size_t n, Slice* result) const;
 

util/thread_local.cc

@@ -38,7 +38,11 @@ class StaticMeta;
 //     | thread 3 |    void*   |    void*   |    void*   | <- ThreadData
 //     ---------------------------------------------------
 struct ThreadData {
-  explicit ThreadData(ThreadLocalPtr::StaticMeta* _inst) : entries(), inst(_inst) {}
+  explicit ThreadData(ThreadLocalPtr::StaticMeta* _inst)
+    : entries(),
+      next(nullptr),
+      prev(nullptr),
+      inst(_inst) {}
   std::vector<Entry> entries;
   ThreadData* next;
   ThreadData* prev;
@@ -300,7 +304,10 @@ void ThreadLocalPtr::StaticMeta::OnThreadExit(void* ptr) {
   delete tls;
 }
 
-ThreadLocalPtr::StaticMeta::StaticMeta() : next_instance_id_(0), head_(this) {
+ThreadLocalPtr::StaticMeta::StaticMeta()
+  : next_instance_id_(0),
+    head_(this),
+    pthread_key_(0) {
   if (pthread_key_create(&pthread_key_, &OnThreadExit) != 0) {
     abort();
   }