diff --git a/src/addhead.cpp b/src/addhead.cpp
index 0b7147b..e3157eb 100644
--- a/src/addhead.cpp
+++ b/src/addhead.cpp
@@ -168,7 +168,7 @@ void AdditionalHeader::Unload()
 {
   is_enable = false;
 
-  for(addheadlist_t::iterator iter = addheadlist.begin(); iter != addheadlist.end(); iter = addheadlist.erase(iter)){
+  for(addheadlist_t::iterator iter = addheadlist.begin(); iter != addheadlist.end(); ++iter){
     ADDHEAD *paddhead = *iter;
     if(paddhead){
       if(paddhead->pregex){
@@ -178,6 +178,7 @@ void AdditionalHeader::Unload()
       delete paddhead;
     }
   }
+  addheadlist.clear();
 }
 
 bool AdditionalHeader::AddHeader(headers_t& meta, const char* path) const
diff --git a/src/cache.cpp b/src/cache.cpp
index 727aac7..6bb7a70 100644
--- a/src/cache.cpp
+++ b/src/cache.cpp
@@ -87,7 +87,7 @@ inline void InitStatCacheTime(struct timespec& ts)
   ts.tv_nsec = 0;
 }
 
-inline int CompareStatCacheTime(struct timespec& ts1, struct timespec& ts2)
+inline int CompareStatCacheTime(const struct timespec& ts1, const struct timespec& ts2)
 {
   // return -1:  ts1 < ts2
   //         0:  ts1 == ts2
@@ -304,7 +304,7 @@ bool StatCache::GetStat(const string& key, struct stat* pst, headers_t* meta, bo
   return false;
 }
 
-bool StatCache::IsNoObjectCache(string& key, bool overcheck)
+bool StatCache::IsNoObjectCache(const string& key, bool overcheck)
 {
   bool is_delete_cache = false;
   string strpath = key;
diff --git a/src/cache.h b/src/cache.h
index 6472685..f210080 100644
--- a/src/cache.h
+++ b/src/cache.h
@@ -110,7 +110,7 @@ class StatCache
     }
 
     // Cache For no object
-    bool IsNoObjectCache(std::string& key, bool overcheck = true);
+    bool IsNoObjectCache(const std::string& key, bool overcheck = true);
     bool AddNoObjectCache(std::string& key);
 
     // Add stat cache
diff --git a/src/curl.cpp b/src/curl.cpp
index c6bdeda..24527dd 100644
--- a/src/curl.cpp
+++ b/src/curl.cpp
@@ -3420,7 +3420,7 @@ int S3fsCurl::PreMultipartPostRequest(const char* tpath, headers_t& meta, string
   return 0;
 }
 
-int S3fsCurl::CompleteMultipartPostRequest(const char* tpath, string& upload_id, etaglist_t& parts)
+int S3fsCurl::CompleteMultipartPostRequest(const char* tpath, const string& upload_id, etaglist_t& parts)
 {
   S3FS_PRN_INFO3("[tpath=%s][parts=%zu]", SAFESTRPTR(tpath), parts.size());
 
@@ -3530,7 +3530,7 @@ int S3fsCurl::MultipartListRequest(string& body)
   return result;
 }
 
-int S3fsCurl::AbortMultipartUpload(const char* tpath, string& upload_id)
+int S3fsCurl::AbortMultipartUpload(const char* tpath, const string& upload_id)
 {
   S3FS_PRN_INFO3("[tpath=%s]", SAFESTRPTR(tpath));
 
@@ -3662,7 +3662,7 @@ int S3fsCurl::UploadMultipartPostRequest(const char* tpath, int part_num, const
   return result;
 }
 
-int S3fsCurl::CopyMultipartPostSetup(const char* from, const char* to, int part_num, string& upload_id, headers_t& meta)
+int S3fsCurl::CopyMultipartPostSetup(const char* from, const char* to, int part_num, const string& upload_id, headers_t& meta)
 {
   S3FS_PRN_INFO3("[from=%s][to=%s][part=%d]", SAFESTRPTR(from), SAFESTRPTR(to), part_num);
 
diff --git a/src/curl.h b/src/curl.h
index da99998..c1441d0 100644
--- a/src/curl.h
+++ b/src/curl.h
@@ -396,7 +396,7 @@ class S3fsCurl
     int GetIAMCredentials(void);
 
     int UploadMultipartPostSetup(const char* tpath, int part_num, const std::string& upload_id);
-    int CopyMultipartPostSetup(const char* from, const char* to, int part_num, std::string& upload_id, headers_t& meta);
+    int CopyMultipartPostSetup(const char* from, const char* to, int part_num, const std::string& upload_id, headers_t& meta);
     bool UploadMultipartPostComplete();
     bool CopyMultipartPostComplete();
 
@@ -494,10 +494,10 @@ class S3fsCurl
     int CheckBucket(void);
     int ListBucketRequest(const char* tpath, const char* query);
     int PreMultipartPostRequest(const char* tpath, headers_t& meta, std::string& upload_id, bool is_copy);
-    int CompleteMultipartPostRequest(const char* tpath, std::string& upload_id, etaglist_t& parts);
+    int CompleteMultipartPostRequest(const char* tpath, const std::string& upload_id, etaglist_t& parts);
     int UploadMultipartPostRequest(const char* tpath, int part_num, const std::string& upload_id);
     int MultipartListRequest(std::string& body);
-    int AbortMultipartUpload(const char* tpath, std::string& upload_id);
+    int AbortMultipartUpload(const char* tpath, const std::string& upload_id);
     int MultipartHeadRequest(const char* tpath, off_t size, headers_t& meta, bool is_copy);
     int MultipartUploadRequest(const char* tpath, headers_t& meta, int fd, bool is_copy);
     int MultipartUploadRequest(const std::string& upload_id, const char* tpath, int fd, off_t offset, off_t size, etaglist_t& list);
diff --git a/src/s3fs.cpp b/src/s3fs.cpp
index 2fcf07b..19dbc0c 100644
--- a/src/s3fs.cpp
+++ b/src/s3fs.cpp
@@ -172,7 +172,7 @@ static int check_parent_object_access(const char* path, int mask);
 static FdEntity* get_local_fent(const char* path, bool is_load = false);
 static bool multi_head_callback(S3fsCurl* s3fscurl);
 static S3fsCurl* multi_head_retry_callback(S3fsCurl* s3fscurl);
-static int readdir_multi_head(const char* path, S3ObjList& head, void* buf, fuse_fill_dir_t filler);
+static int readdir_multi_head(const char* path, const S3ObjList& head, void* buf, fuse_fill_dir_t filler);
 static int list_bucket(const char* path, S3ObjList& head, const char* delimiter, bool check_content_only = false);
 static int directory_empty(const char* path);
 static bool is_truncated(xmlDocPtr doc);
@@ -2440,7 +2440,7 @@ static S3fsCurl* multi_head_retry_callback(S3fsCurl* s3fscurl)
   return newcurl;
 }
 
-static int readdir_multi_head(const char* path, S3ObjList& head, void* buf, fuse_fill_dir_t filler)
+static int readdir_multi_head(const char* path, const S3ObjList& head, void* buf, fuse_fill_dir_t filler)
 {
   S3fsMultiCurl curlmulti(S3fsCurl::GetMaxMultiRequest());
   s3obj_list_t  headlist;
@@ -2750,7 +2750,7 @@ static bool GetXmlNsUrl(xmlDocPtr doc, string& nsurl)
   bool result = false;
 
   if(!doc){
-    return result;
+    return false;
   }
   if((tmLast + 60) < time(NULL)){
     // refresh
@@ -2877,7 +2877,7 @@ static bool is_truncated(xmlDocPtr doc)
 
   xmlChar* strTruncate = get_base_exp(doc, "IsTruncated");
   if(!strTruncate){
-    return result;
+    return false;
   }
   if(0 == strcasecmp((const char*)strTruncate, "true")){
     result = true;
diff --git a/src/s3fs_util.cpp b/src/s3fs_util.cpp
index 0e370b4..2a1c9f8 100644
--- a/src/s3fs_util.cpp
+++ b/src/s3fs_util.cpp
@@ -994,18 +994,18 @@ bool simple_parse_xml(const char* data, size_t len, const char* key, std::string
   bool result = false;
 
   if(!data || !key){
-    return result;
+    return false;
   }
   value.clear();
 
   xmlDocPtr doc;
   if(NULL == (doc = xmlReadMemory(data, len, "", NULL, 0))){
-    return result;
+    return false;
   }
 
   if(NULL == doc->children){
     S3FS_XMLFREEDOC(doc);
-    return result;
+    return false;
   }
   for(xmlNodePtr cur_node = doc->children->children; NULL != cur_node; cur_node = cur_node->next){
     // For DEBUG