Remove extern from function declarations.

External linkage is the default for function declarations in C++.

This also fixes ClangTidy errors generated by removing the "extern"
keyword as described above.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188730416

20 files changed, 103 insertions, 110 deletions

diff --git a/db/builder.h b/db/builder.h
index 62431fc..0289730 100644
--- a/db/builder.h
+++ b/db/builder.h
@@ -22,12 +22,12 @@ class VersionEdit;
 // *meta will be filled with metadata about the generated table.
 // If no data is present in *iter, meta->file_size will be set to
 // zero, and no Table file will be produced.
-extern Status BuildTable(const std::string& dbname,
-                         Env* env,
-                         const Options& options,
-                         TableCache* table_cache,
-                         Iterator* iter,
-                         FileMetaData* meta);
+Status BuildTable(const std::string& dbname,
+                  Env* env,
+                  const Options& options,
+                  TableCache* table_cache,
+                  Iterator* iter,
+                  FileMetaData* meta);
 
 }  // namespace leveldb
 
diff --git a/db/db_impl.h b/db/db_impl.h
index 8ff323e..3861b86 100644
--- a/db/db_impl.h
+++ b/db/db_impl.h
@@ -201,10 +201,10 @@ class DBImpl : public DB {
 
 // Sanitize db options.  The caller should delete result.info_log if
 // it is not equal to src.info_log.
-extern Options SanitizeOptions(const std::string& db,
-                               const InternalKeyComparator* icmp,
-                               const InternalFilterPolicy* ipolicy,
-                               const Options& src);
+Options SanitizeOptions(const std::string& db,
+                        const InternalKeyComparator* icmp,
+                        const InternalFilterPolicy* ipolicy,
+                        const Options& src);
 
 }  // namespace leveldb
 
diff --git a/db/db_iter.h b/db/db_iter.h
index 04927e9..262840e 100644
--- a/db/db_iter.h
+++ b/db/db_iter.h
@@ -16,12 +16,11 @@ class DBImpl;
 // Return a new iterator that converts internal keys (yielded by
 // "*internal_iter") that were live at the specified "sequence" number
 // into appropriate user keys.
-extern Iterator* NewDBIterator(
-    DBImpl* db,
-    const Comparator* user_key_comparator,
-    Iterator* internal_iter,
-    SequenceNumber sequence,
-    uint32_t seed);
+Iterator* NewDBIterator(DBImpl* db,
+                        const Comparator* user_key_comparator,
+                        Iterator* internal_iter,
+                        SequenceNumber sequence,
+                        uint32_t seed);
 
 }  // namespace leveldb
 
diff --git a/db/dbformat.h b/db/dbformat.h
index 2e93669..c4d9575 100644
--- a/db/dbformat.h
+++ b/db/dbformat.h
@@ -84,15 +84,13 @@ inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) {
 }
 
 // Append the serialization of "key" to *result.
-extern void AppendInternalKey(std::string* result,
-                              const ParsedInternalKey& key);
+void AppendInternalKey(std::string* result, const ParsedInternalKey& key);
 
 // Attempt to parse an internal key from "internal_key".  On success,
 // stores the parsed data in "*result", and returns true.
 //
 // On error, returns false, leaves "*result" in an undefined state.
-extern bool ParseInternalKey(const Slice& internal_key,
-                             ParsedInternalKey* result);
+bool ParseInternalKey(const Slice& internal_key, ParsedInternalKey* result);
 
 // Returns the user key portion of an internal key.
 inline Slice ExtractUserKey(const Slice& internal_key) {
diff --git a/db/filename.cc b/db/filename.cc
index da32946..6539bbe 100644
--- a/db/filename.cc
+++ b/db/filename.cc
@@ -12,31 +12,31 @@
 namespace leveldb {
 
 // A utility routine: write "data" to the named file and Sync() it.
-extern Status WriteStringToFileSync(Env* env, const Slice& data,
-                                    const std::string& fname);
+Status WriteStringToFileSync(Env* env, const Slice& data,
+                             const std::string& fname);
 
-static std::string MakeFileName(const std::string& name, uint64_t number,
+static std::string MakeFileName(const std::string& dbname, uint64_t number,
                                 const char* suffix) {
   char buf[100];
   snprintf(buf, sizeof(buf), "/%06llu.%s",
            static_cast<unsigned long long>(number),
            suffix);
-  return name + buf;
+  return dbname + buf;
 }
 
-std::string LogFileName(const std::string& name, uint64_t number) {
+std::string LogFileName(const std::string& dbname, uint64_t number) {
   assert(number > 0);
-  return MakeFileName(name, number, "log");
+  return MakeFileName(dbname, number, "log");
 }
 
-std::string TableFileName(const std::string& name, uint64_t number) {
+std::string TableFileName(const std::string& dbname, uint64_t number) {
   assert(number > 0);
-  return MakeFileName(name, number, "ldb");
+  return MakeFileName(dbname, number, "ldb");
 }
 
-std::string SSTTableFileName(const std::string& name, uint64_t number) {
+std::string SSTTableFileName(const std::string& dbname, uint64_t number) {
   assert(number > 0);
-  return MakeFileName(name, number, "sst");
+  return MakeFileName(dbname, number, "sst");
 }
 
 std::string DescriptorFileName(const std::string& dbname, uint64_t number) {
@@ -77,10 +77,10 @@ std::string OldInfoLogFileName(const std::string& dbname) {
 //    dbname/LOG.old
 //    dbname/MANIFEST-[0-9]+
 //    dbname/[0-9]+.(log|sst|ldb)
-bool ParseFileName(const std::string& fname,
+bool ParseFileName(const std::string& filename,
                    uint64_t* number,
                    FileType* type) {
-  Slice rest(fname);
+  Slice rest(filename);
   if (rest == "CURRENT") {
     *number = 0;
     *type = kCurrentFile;
diff --git a/db/filename.h b/db/filename.h
index 87a7526..62cb3ef 100644
--- a/db/filename.h
+++ b/db/filename.h
@@ -30,55 +30,53 @@ enum FileType {
 // Return the name of the log file with the specified number
 // in the db named by "dbname".  The result will be prefixed with
 // "dbname".
-extern std::string LogFileName(const std::string& dbname, uint64_t number);
+std::string LogFileName(const std::string& dbname, uint64_t number);
 
 // Return the name of the sstable with the specified number
 // in the db named by "dbname".  The result will be prefixed with
 // "dbname".
-extern std::string TableFileName(const std::string& dbname, uint64_t number);
+std::string TableFileName(const std::string& dbname, uint64_t number);
 
 // Return the legacy file name for an sstable with the specified number
 // in the db named by "dbname". The result will be prefixed with
 // "dbname".
-extern std::string SSTTableFileName(const std::string& dbname, uint64_t number);
+std::string SSTTableFileName(const std::string& dbname, uint64_t number);
 
 // Return the name of the descriptor file for the db named by
 // "dbname" and the specified incarnation number.  The result will be
 // prefixed with "dbname".
-extern std::string DescriptorFileName(const std::string& dbname,
-                                      uint64_t number);
+std::string DescriptorFileName(const std::string& dbname, uint64_t number);
 
 // Return the name of the current file.  This file contains the name
 // of the current manifest file.  The result will be prefixed with
 // "dbname".
-extern std::string CurrentFileName(const std::string& dbname);
+std::string CurrentFileName(const std::string& dbname);
 
 // Return the name of the lock file for the db named by
 // "dbname".  The result will be prefixed with "dbname".
-extern std::string LockFileName(const std::string& dbname);
+std::string LockFileName(const std::string& dbname);
 
 // Return the name of a temporary file owned by the db named "dbname".
 // The result will be prefixed with "dbname".
-extern std::string TempFileName(const std::string& dbname, uint64_t number);
+std::string TempFileName(const std::string& dbname, uint64_t number);
 
 // Return the name of the info log file for "dbname".
-extern std::string InfoLogFileName(const std::string& dbname);
+std::string InfoLogFileName(const std::string& dbname);
 
 // Return the name of the old info log file for "dbname".
-extern std::string OldInfoLogFileName(const std::string& dbname);
+std::string OldInfoLogFileName(const std::string& dbname);
 
 // If filename is a leveldb file, store the type of the file in *type.
 // The number encoded in the filename is stored in *number.  If the
 // filename was successfully parsed, returns true.  Else return false.
-extern bool ParseFileName(const std::string& filename,
-                          uint64_t* number,
-                          FileType* type);
+bool ParseFileName(const std::string& filename,
+                   uint64_t* number,
+                   FileType* type);
 
 // Make the CURRENT file point to the descriptor file with the
 // specified number.
-extern Status SetCurrentFile(Env* env, const std::string& dbname,
-                             uint64_t descriptor_number);
-
+Status SetCurrentFile(Env* env, const std::string& dbname,
+                      uint64_t descriptor_number);
 
 }  // namespace leveldb
 
diff --git a/db/version_set.h b/db/version_set.h
index c4e7ac3..80d448a 100644
--- a/db/version_set.h
+++ b/db/version_set.h
@@ -39,9 +39,9 @@ class WritableFile;
 // Return the smallest index i such that files[i]->largest >= key.
 // Return files.size() if there is no such file.
 // REQUIRES: "files" contains a sorted list of non-overlapping files.
-extern int FindFile(const InternalKeyComparator& icmp,
-                    const std::vector<FileMetaData*>& files,
-                    const Slice& key);
+int FindFile(const InternalKeyComparator& icmp,
+             const std::vector<FileMetaData*>& files,
+             const Slice& key);
 
 // Returns true iff some file in "files" overlaps the user key range
 // [*smallest,*largest].
@@ -49,12 +49,11 @@ extern int FindFile(const InternalKeyComparator& icmp,
 // largest==NULL represents a key largest than all keys in the DB.
 // REQUIRES: If disjoint_sorted_files, files[] contains disjoint ranges
 //           in sorted order.
-extern bool SomeFileOverlapsRange(
-    const InternalKeyComparator& icmp,
-    bool disjoint_sorted_files,
-    const std::vector<FileMetaData*>& files,
-    const Slice* smallest_user_key,
-    const Slice* largest_user_key);
+bool SomeFileOverlapsRange(const InternalKeyComparator& icmp,
+                           bool disjoint_sorted_files,
+                           const std::vector<FileMetaData*>& files,
+                           const Slice* smallest_user_key,
+                           const Slice* largest_user_key);
 
 class Version {
  public:
diff --git a/include/leveldb/env.h b/include/leveldb/env.h
index d698169..9d8ebfe 100644
--- a/include/leveldb/env.h
+++ b/include/leveldb/env.h
@@ -271,7 +271,7 @@ class LEVELDB_EXPORT FileLock {
 };
 
 // Log the specified data to *info_log if info_log is non-NULL.
-extern void Log(Logger* info_log, const char* format, ...)
+void Log(Logger* info_log, const char* format, ...)
 #   if defined(__GNUC__) || defined(__clang__)
     __attribute__((__format__ (__printf__, 2, 3)))
 #   endif
diff --git a/port/port_example.h b/port/port_example.h
index b5190e6..88fc9cb 100644
--- a/port/port_example.h
+++ b/port/port_example.h
@@ -70,7 +70,7 @@ class CondVar {
 //      port::InitOnce(&init_control, &Initializer);
 typedef intptr_t OnceType;
 #define LEVELDB_ONCE_INIT 0
-extern void InitOnce(port::OnceType*, void (*initializer)());
+void InitOnce(port::OnceType*, void (*initializer)());
 
 // A type that holds a pointer that can be read or written atomically
 // (i.e., without word-tearing.)
@@ -105,14 +105,14 @@ class AtomicPointer {
 
 // Store the snappy compression of "input[0,input_length-1]" in *output.
 // Returns false if snappy is not supported by this port.
-extern bool Snappy_Compress(const char* input, size_t input_length,
-                            std::string* output);
+bool Snappy_Compress(const char* input, size_t input_length,
+                     std::string* output);
 
 // If input[0,input_length-1] looks like a valid snappy compressed
 // buffer, store the size of the uncompressed data in *result and
 // return true.  Else return false.
-extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
-                                         size_t* result);
+bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                  size_t* result);
 
 // Attempt to snappy uncompress input[0,input_length-1] into *output.
 // Returns true if successful, false if the input is invalid lightweight
@@ -121,15 +121,15 @@ extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
 // REQUIRES: at least the first "n" bytes of output[] must be writable
 // where "n" is the result of a successful call to
 // Snappy_GetUncompressedLength.
-extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
-                              char* output);
+bool Snappy_Uncompress(const char* input_data, size_t input_length,
+                       char* output);
 
 // ------------------ Miscellaneous -------------------
 
 // If heap profiling is not supported, returns false.
 // Else repeatedly calls (*func)(arg, data, n) and then returns true.
 // The concatenation of all "data[0,n-1]" fragments is the heap profile.
-extern bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg);
+bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg);
 
 // Extend the CRC to include the first n bytes of buf.
 //
diff --git a/port/port_posix.h b/port/port_posix.h
index 5bfc12e..ce52042 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -106,7 +106,7 @@ class CondVar {
 
 typedef pthread_once_t OnceType;
 #define LEVELDB_ONCE_INIT PTHREAD_ONCE_INIT
-extern void InitOnce(OnceType* once, void (*initializer)());
+void InitOnce(OnceType* once, void (*initializer)());
 
 inline bool Snappy_Compress(const char* input, size_t length,
                             ::std::string* output) {
diff --git a/table/format.h b/table/format.h
index 6c0b80c..144ff55 100644
--- a/table/format.h
+++ b/table/format.h
@@ -91,10 +91,10 @@ struct BlockContents {
 
 // Read the block identified by "handle" from "file".  On failure
 // return non-OK.  On success fill *result and return OK.
-extern Status ReadBlock(RandomAccessFile* file,
-                        const ReadOptions& options,
-                        const BlockHandle& handle,
-                        BlockContents* result);
+Status ReadBlock(RandomAccessFile* file,
+                 const ReadOptions& options,
+                 const BlockHandle& handle,
+                 BlockContents* result);
 
 // Implementation details follow.  Clients should ignore,
 
diff --git a/table/merger.h b/table/merger.h
index 91ddd80..bafdf5a 100644
--- a/table/merger.h
+++ b/table/merger.h
@@ -18,7 +18,7 @@ class Iterator;
 // key is present in K child iterators, it will be yielded K times.
 //
 // REQUIRES: n >= 0
-extern Iterator* NewMergingIterator(
+Iterator* NewMergingIterator(
     const Comparator* comparator, Iterator** children, int n);
 
 }  // namespace leveldb
diff --git a/table/two_level_iterator.h b/table/two_level_iterator.h
index 629ca34..a93ba89 100644
--- a/table/two_level_iterator.h
+++ b/table/two_level_iterator.h
@@ -20,7 +20,7 @@ struct ReadOptions;
 //
 // Uses a supplied function to convert an index_iter value into
 // an iterator over the contents of the corresponding block.
-extern Iterator* NewTwoLevelIterator(
+Iterator* NewTwoLevelIterator(
     Iterator* index_iter,
     Iterator* (*block_function)(
         void* arg,
diff --git a/util/coding.h b/util/coding.h
index 3993c4a..5c4d40e 100644
--- a/util/coding.h
+++ b/util/coding.h
@@ -19,38 +19,38 @@
 namespace leveldb {
 
 // Standard Put... routines append to a string
-extern void PutFixed32(std::string* dst, uint32_t value);
-extern void PutFixed64(std::string* dst, uint64_t value);
-extern void PutVarint32(std::string* dst, uint32_t value);
-extern void PutVarint64(std::string* dst, uint64_t value);
-extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
+void PutFixed32(std::string* dst, uint32_t value);
+void PutFixed64(std::string* dst, uint64_t value);
+void PutVarint32(std::string* dst, uint32_t value);
+void PutVarint64(std::string* dst, uint64_t value);
+void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
 
 // Standard Get... routines parse a value from the beginning of a Slice
 // and advance the slice past the parsed value.
-extern bool GetVarint32(Slice* input, uint32_t* value);
-extern bool GetVarint64(Slice* input, uint64_t* value);
-extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
+bool GetVarint32(Slice* input, uint32_t* value);
+bool GetVarint64(Slice* input, uint64_t* value);
+bool GetLengthPrefixedSlice(Slice* input, Slice* result);
 
 // Pointer-based variants of GetVarint...  These either store a value
 // in *v and return a pointer just past the parsed value, or return
 // NULL on error.  These routines only look at bytes in the range
 // [p..limit-1]
-extern const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v);
-extern const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v);
+const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v);
+const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v);
 
 // Returns the length of the varint32 or varint64 encoding of "v"
-extern int VarintLength(uint64_t v);
+int VarintLength(uint64_t v);
 
 // Lower-level versions of Put... that write directly into a character buffer
 // REQUIRES: dst has enough space for the value being written
-extern void EncodeFixed32(char* dst, uint32_t value);
-extern void EncodeFixed64(char* dst, uint64_t value);
+void EncodeFixed32(char* dst, uint32_t value);
+void EncodeFixed64(char* dst, uint64_t value);
 
 // Lower-level versions of Put... that write directly into a character buffer
 // and return a pointer just past the last byte written.
 // REQUIRES: dst has enough space for the value being written
-extern char* EncodeVarint32(char* dst, uint32_t value);
-extern char* EncodeVarint64(char* dst, uint64_t value);
+char* EncodeVarint32(char* dst, uint32_t value);
+char* EncodeVarint64(char* dst, uint64_t value);
 
 // Lower-level versions of Get... that read directly from a character buffer
 // without any bounds checking.
@@ -83,9 +83,9 @@ inline uint64_t DecodeFixed64(const char* ptr) {
 }
 
 // Internal routine for use by fallback path of GetVarint32Ptr
-extern const char* GetVarint32PtrFallback(const char* p,
-                                          const char* limit,
-                                          uint32_t* value);
+const char* GetVarint32PtrFallback(const char* p,
+                                   const char* limit,
+                                   uint32_t* value);
 inline const char* GetVarint32Ptr(const char* p,
                                   const char* limit,
                                   uint32_t* value) {
diff --git a/util/crc32c.h b/util/crc32c.h
index 1d7e5c0..7864688 100644
--- a/util/crc32c.h
+++ b/util/crc32c.h
@@ -14,7 +14,7 @@ namespace crc32c {
 // Return the crc32c of concat(A, data[0,n-1]) where init_crc is the
 // crc32c of some string A.  Extend() is often used to maintain the
 // crc32c of a stream of data.
-extern uint32_t Extend(uint32_t init_crc, const char* data, size_t n);
+uint32_t Extend(uint32_t init_crc, const char* data, size_t n);
 
 // Return the crc32c of data[0,n-1]
 inline uint32_t Value(const char* data, size_t n) {
diff --git a/util/hash.h b/util/hash.h
index 8889d56..74bdb6e 100644
--- a/util/hash.h
+++ b/util/hash.h
@@ -12,8 +12,8 @@
 
 namespace leveldb {
 
-extern uint32_t Hash(const char* data, size_t n, uint32_t seed);
+uint32_t Hash(const char* data, size_t n, uint32_t seed);
 
-}
+}  // namespace leveldb
 
 #endif  // STORAGE_LEVELDB_UTIL_HASH_H_
diff --git a/util/logging.h b/util/logging.h
index 1b450d2..13351a2 100644
--- a/util/logging.h
+++ b/util/logging.h
@@ -19,24 +19,24 @@ class Slice;
 class WritableFile;
 
 // Append a human-readable printout of "num" to *str
-extern void AppendNumberTo(std::string* str, uint64_t num);
+void AppendNumberTo(std::string* str, uint64_t num);
 
 // Append a human-readable printout of "value" to *str.
 // Escapes any non-printable characters found in "value".
-extern void AppendEscapedStringTo(std::string* str, const Slice& value);
+void AppendEscapedStringTo(std::string* str, const Slice& value);
 
 // Return a human-readable printout of "num"
-extern std::string NumberToString(uint64_t num);
+std::string NumberToString(uint64_t num);
 
 // Return a human-readable version of "value".
 // Escapes any non-printable characters found in "value".
-extern std::string EscapeString(const Slice& value);
+std::string EscapeString(const Slice& value);
 
 // Parse a human-readable number from "*in" into *value.  On success,
 // advances "*in" past the consumed number and sets "*val" to the
 // numeric value.  Otherwise, returns false and leaves *in in an
 // unspecified state.
-extern bool ConsumeDecimalNumber(Slice* in, uint64_t* val);
+bool ConsumeDecimalNumber(Slice* in, uint64_t* val);
 
 }  // namespace leveldb
 
diff --git a/util/testharness.h b/util/testharness.h
index da4fe68..029e5c7 100644
--- a/util/testharness.h
+++ b/util/testharness.h
@@ -27,15 +27,15 @@ namespace test {
 //
 // Returns 0 if all tests pass.
 // Dies or returns a non-zero value if some test fails.
-extern int RunAllTests();
+int RunAllTests();
 
 // Return the directory to use for temporary storage.
-extern std::string TmpDir();
+std::string TmpDir();
 
 // Return a randomization seed for this run.  Typically returns the
 // same number on repeated invocations of this binary, but automated
 // runs may be able to vary the seed.
-extern int RandomSeed();
+int RandomSeed();
 
 // An instance of Tester is allocated to hold temporary state during
 // the execution of an assertion.
@@ -129,8 +129,7 @@ void TCONCAT(_Test_,name)::_Run()
 
 // Register the specified test.  Typically not used directly, but
 // invoked via the macro expansion of TEST.
-extern bool RegisterTest(const char* base, const char* name, void (*func)());
-
+bool RegisterTest(const char* base, const char* name, void (*func)());
 
 }  // namespace test
 }  // namespace leveldb
diff --git a/util/testutil.cc b/util/testutil.cc
index bee56bf..9d8079c 100644
--- a/util/testutil.cc
+++ b/util/testutil.cc
@@ -31,8 +31,8 @@ std::string RandomKey(Random* rnd, int len) {
 }
 
 
-extern Slice CompressibleString(Random* rnd, double compressed_fraction,
-                                size_t len, std::string* dst) {
+Slice CompressibleString(Random* rnd, double compressed_fraction,
+                         size_t len, std::string* dst) {
   int raw = static_cast<int>(len * compressed_fraction);
   if (raw < 1) raw = 1;
   std::string raw_data;
diff --git a/util/testutil.h b/util/testutil.h
index d7e4583..8726bf7 100644
--- a/util/testutil.h
+++ b/util/testutil.h
@@ -14,17 +14,17 @@ namespace test {
 
 // Store in *dst a random string of length "len" and return a Slice that
 // references the generated data.
-extern Slice RandomString(Random* rnd, int len, std::string* dst);
+Slice RandomString(Random* rnd, int len, std::string* dst);
 
 // Return a random key with the specified length that may contain interesting
 // characters (e.g. \x00, \xff, etc.).
-extern std::string RandomKey(Random* rnd, int len);
+std::string RandomKey(Random* rnd, int len);
 
 // Store in *dst a string of length "len" that will compress to
 // "N*compressed_fraction" bytes and return a Slice that references
 // the generated data.
-extern Slice CompressibleString(Random* rnd, double compressed_fraction,
-                                size_t len, std::string* dst);
+Slice CompressibleString(Random* rnd, double compressed_fraction,
+                         size_t len, std::string* dst);
 
 // A wrapper that allows injection of errors.
 class ErrorEnv : public EnvWrapper {