Enable MS compiler warning c4244.

Mostly due to the fact that there are differences in sizes of int,long
  on 64 bit systems vs GNU.

CMakeLists.txt

@@ -59,8 +59,8 @@ add_custom_command(OUTPUT ${BUILD_VERSION_CC}
 add_custom_target(GenerateBuildVersion DEPENDS ${BUILD_VERSION_CC})
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /Zi /nologo  /EHsc /GS /Gd /GR /GF /fp:precise /Zc:wchar_t /Zc:forScope /errorReport:queue")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /FC /d2Zi+ /W3 /WX /wd4127 /wd4267 /wd4800 /wd4996")
 
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /FC /d2Zi+ /W3 /WX /wd4127 /wd4800 /wd4996")
 
 # Used to run CI build and tests so we can run faster
 set(OPTIMIZE_DEBUG_DEFAULT 0)        # Debug build is unoptimized by default use -DOPTDBG=1 to optimize

db/compaction_job_stats_test.cc

@@ -551,8 +551,9 @@ uint64_t EstimatedFileSize(
   const size_t kFooterSize = 512;
 
   uint64_t data_size =
-      static_cast<uint64_t>(num_records * (key_size + 
-         value_size * compression_ratio + kPerKeyOverhead));
+    static_cast<uint64_t>(
+      num_records * (key_size + value_size * compression_ratio +
+      kPerKeyOverhead));
 
   return data_size + kFooterSize
          + num_records * bloom_bits_per_key / 8      // filter block

db/version_set.cc

@@ -738,22 +738,22 @@ uint64_t VersionStorageInfo::GetEstimatedActiveKeys() const {
   // (2) keys are directly overwritten
   // (3) deletion on non-existing keys
   // (4) low number of samples
-  if (num_samples_ == 0) {
+  if (current_num_samples_ == 0) {
     return 0;
   }
 
-  if (accumulated_num_non_deletions_ <= accumulated_num_deletions_) {
+  if (current_num_non_deletions_ <= current_num_deletions_) {
     return 0;
   }
 
-  uint64_t est = accumulated_num_non_deletions_ - accumulated_num_deletions_;
+  uint64_t est = current_num_non_deletions_ - current_num_deletions_;
 
   uint64_t file_count = 0;
   for (int level = 0; level < num_levels_; ++level) {
     file_count += files_[level].size();
   }
 
-  if (num_samples_ < file_count) {
+  if (current_num_samples_ < file_count) {
     // casting to avoid overflowing
     return 
       static_cast<uint64_t>(
@@ -888,7 +888,7 @@ void Version::Get(const ReadOptions& read_options, const LookupKey& k,
   GetContext get_context(
       user_comparator(), merge_operator_, info_log_, db_statistics_,
       status->ok() ? GetContext::kNotFound : GetContext::kMerge, user_key,
-      value, value_found, merge_context, this->env_, seq);
+      value, value_found, merge_context, this->env_);
 
   FilePicker fp(
       storage_info_.files_, user_key, ikey, &storage_info_.level_files_brief_,