diff --git a/include/spdlog/details/fast_istostr.h b/include/spdlog/details/fast_istostr.h
index 5b7cdc12..55500955 100644
--- a/include/spdlog/details/fast_istostr.h
+++ b/include/spdlog/details/fast_istostr.h
@@ -49,7 +49,7 @@ const char digit_pairs[201] =
 };
 
 
-inline std::string& fast_itostr(int n, std::string& s, int padding)
+inline std::string& fast_itostr(int n, std::string& s, size_t padding)
 {
     if (n == 0)
     {
@@ -58,9 +58,9 @@ inline std::string& fast_itostr(int n, std::string& s, int padding)
     }
 
     int sign = -(n < 0);
-    unsigned int val = (n^sign) - sign;
+    unsigned int val = static_cast<unsigned int>((n^sign) - sign);
 
-    int size;
+    size_t size;
     if (val >= 10000)
     {
         if (val >= 10000000)
@@ -111,14 +111,14 @@ inline std::string& fast_itostr(int n, std::string& s, int padding)
     c += size - 1;
     while (val >= 100)
     {
-        int pos = val % 100;
+        size_t pos = val % 100;
         val /= 100;
         *(short*)(c - 1) = *(short*)(digit_pairs + 2 * pos);
         c -= 2;
     }
     while (val > 0)
     {
-        *c-- = '0' + (val % 10);
+        *c-- = static_cast<char>('0' + (val % 10));
         val /= 10;
     }
 
diff --git a/include/spdlog/details/fast_oss.h b/include/spdlog/details/fast_oss.h
index cb7f8eb5..3ac35ded 100644
--- a/include/spdlog/details/fast_oss.h
+++ b/include/spdlog/details/fast_oss.h
@@ -158,7 +158,7 @@ public:
     }
 
     // put int and pad with zeroes if smalled than min_width
-    void put_int(int n, int padding)
+    void put_int(int n, size_t padding)
     {
         std::string s;
         details::fast_itostr(n, s, padding);
diff --git a/include/spdlog/details/file_helper.h b/include/spdlog/details/file_helper.h
index b5a43fee..da389d8d 100644
--- a/include/spdlog/details/file_helper.h
+++ b/include/spdlog/details/file_helper.h
@@ -55,6 +55,7 @@ public:
         _flush_countdown(flush_inverval) {};
 
     file_helper(const file_helper&) = delete;
+    file_helper& operator=(const file_helper&) = delete;
 
     ~file_helper()
     {
diff --git a/include/spdlog/details/os.h b/include/spdlog/details/os.h
index 88459512..8eab7b85 100644
--- a/include/spdlog/details/os.h
+++ b/include/spdlog/details/os.h
@@ -134,6 +134,7 @@ inline int utc_minutes_offset(const std::tm& tm = localtime())
 {
 
 #ifdef _WIN32
+    (void)tm; // avoid unused param warning
     DYNAMIC_TIME_ZONE_INFORMATION tzinfo;
     auto rv = GetDynamicTimeZoneInformation(&tzinfo);
     if (!rv)
diff --git a/include/spdlog/details/pattern_formatter_impl.h b/include/spdlog/details/pattern_formatter_impl.h
index 8de6beb9..e063583c 100644
--- a/include/spdlog/details/pattern_formatter_impl.h
+++ b/include/spdlog/details/pattern_formatter_impl.h
@@ -42,6 +42,7 @@ namespace details
 class flag_formatter
 {
 public:
+    virtual ~flag_formatter() {}
     virtual void format(details::log_msg& msg) = 0;
 };
 
@@ -295,6 +296,9 @@ class T_formatter :public flag_formatter
 class z_formatter :public flag_formatter
 {
 public:
+    z_formatter() {}
+    z_formatter(const z_formatter&) = delete;
+    z_formatter& operator=(const z_formatter&) = delete;
 
     void format(log_msg& msg) override
     {
@@ -312,6 +316,8 @@ public:
 private:
     log_clock::time_point _last_update;
     std::string _value;
+    std::mutex _mutex;
+
     std::string get_value(const log_msg& msg)
     {
         int total_minutes = os::utc_minutes_offset(msg.tm_time);
@@ -324,7 +330,7 @@ private:
         oss.put_int(m, 2);
         return oss.str();
     }
-    std::mutex _mutex;
+
 };
 
 
@@ -451,7 +457,7 @@ inline void spdlog::pattern_formatter::handle_flag(char flag)
 {
     switch (flag)
     {
-        // logger name
+    // logger name
     case 'n':
         _formatters.push_back(std::unique_ptr<details::flag_formatter>(new details::name_formatter()));
         break;
diff --git a/include/spdlog/details/registry.h b/include/spdlog/details/registry.h
index 7ac6c564..e84adad0 100644
--- a/include/spdlog/details/registry.h
+++ b/include/spdlog/details/registry.h
@@ -122,6 +122,7 @@ public:
 private:
     registry() = default;
     registry(const registry&) = delete;
+    registry& operator=(const registry&) = delete;
     std::mutex _mutex;
     std::unordered_map <std::string, std::shared_ptr<logger>> _loggers;
     formatter_ptr _formatter;
diff --git a/include/spdlog/formatter.h b/include/spdlog/formatter.h
index e502fd90..35ea0416 100644
--- a/include/spdlog/formatter.h
+++ b/include/spdlog/formatter.h
@@ -44,6 +44,7 @@ class pattern_formatter : public formatter
 public:
     explicit pattern_formatter(const std::string& pattern);
     pattern_formatter(const pattern_formatter&) = delete;
+    pattern_formatter& operator=(const pattern_formatter&) = delete;
     void format(details::log_msg& msg) override;
 private:
     const std::string _pattern;