Fix warnings when using API (#12066)

Summary:
Fixes https://github.com/facebook/rocksdb/issues/11457.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12066

Reviewed By: cbi42

Differential Revision: D51259966

Pulled By: ajkr

fbshipit-source-id: a158b6f341b6b48233d917bfe4d00b639dbd8619

include/rocksdb/advanced_options.h

@@ -714,7 +714,7 @@ struct AdvancedColumnFamilyOptions {
   //
   // Dynamically changeable through SetOptions() API
   std::vector<int> max_bytes_for_level_multiplier_additional =
-      std::vector<int>(num_levels, 1);
+      std::vector<int>(static_cast<size_t>(num_levels), 1);
 
   // We try to limit number of bytes in one compaction to be lower than this
   // threshold. But it's not guaranteed.

include/rocksdb/sst_file_writer.h

@@ -46,7 +46,7 @@ struct ExternalSstFileInfo {
                       const std::string& _smallest_key,
                       const std::string& _largest_key,
                       SequenceNumber _sequence_number, uint64_t _file_size,
-                      int32_t _num_entries, int32_t _version)
+                      uint64_t _num_entries, int32_t _version)
       : file_path(_file_path),
         smallest_key(_smallest_key),
         largest_key(_largest_key),

include/rocksdb/write_batch.h

@@ -43,13 +43,13 @@ struct SavePoints;
 struct SliceParts;
 
 struct SavePoint {
-  size_t size;  // size of rep_
-  int count;    // count of elements in rep_
+  size_t size;     // size of rep_
+  uint32_t count;  // count of elements in rep_
   uint32_t content_flags;
 
   SavePoint() : size(0), count(0), content_flags(0) {}
 
-  SavePoint(size_t _size, int _count, uint32_t _flags)
+  SavePoint(size_t _size, uint32_t _count, uint32_t _flags)
       : size(_size), count(_count), content_flags(_flags) {}
 
   void clear() {