Add an optional final qualifier to types

When building with GCC's -Wfinal-types, a lot of types of spdlog
are marked as being more optimizable if they were marked final.

This patch adds a possibility for the user of the library to `#define SPDLOG_FINAL final`
and enjoy potentially better performance : GCC is then able to replace virtual calls by true
function calls if it can ensure that there are no derived types).

By default SPDLOG_FINAL is defined to nothing to not break existing code that
may be inheriting of some of these types for some reason.

8 files changed, 41 insertions, 35 deletions

diff --git a/include/spdlog/async_logger.h b/include/spdlog/async_logger.h
index cda6be4f..a86d2190 100644
--- a/include/spdlog/async_logger.h
+++ b/include/spdlog/async_logger.h
@@ -31,7 +31,7 @@ namespace details
 class async_log_helper;
 }
 
-class async_logger :public logger
+class async_logger SPDLOG_FINAL :public logger
 {
 public:
     template<class It>
diff --git a/include/spdlog/common.h b/include/spdlog/common.h
index a0a227ef..dfecb082 100644
--- a/include/spdlog/common.h
+++ b/include/spdlog/common.h
@@ -29,6 +29,12 @@
 #define SPDLOG_CONSTEXPR constexpr
 #endif
 
+// If an user of the library is not inheriting from the types provided by it,
+// he can #define SPDLOG_FINAL final to get additional optimizations
+#if !defined(SPDLOG_FINAL)
+#define SPDLOG_FINAL
+#endif
+
 #if defined(__GNUC__)  || defined(__clang__)
 #define SPDLOG_DEPRECATED __attribute__((deprecated))
 #elif defined(_MSC_VER)
diff --git a/include/spdlog/details/pattern_formatter_impl.h b/include/spdlog/details/pattern_formatter_impl.h
index 123024f7..77f0f20b 100644
--- a/include/spdlog/details/pattern_formatter_impl.h
+++ b/include/spdlog/details/pattern_formatter_impl.h
@@ -99,7 +99,7 @@ static const days_array& full_days()
     static const days_array arr{ { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" } };
     return arr;
 }
-class A_formatter:public flag_formatter
+class A_formatter SPDLOG_FINAL :public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -128,7 +128,7 @@ static const months_array& full_months()
     static const months_array arr{ { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" } };
     return arr;
 }
-class B_formatter:public flag_formatter
+class B_formatter SPDLOG_FINAL :public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -153,7 +153,7 @@ static fmt::MemoryWriter& pad_n_join(fmt::MemoryWriter& w, int v1, int v2, int v
 
 
 //Date and time representation (Thu Aug 23 15:35:46 2014)
-class c_formatter:public flag_formatter
+class c_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -164,7 +164,7 @@ class c_formatter:public flag_formatter
 
 
 // year - 2 digit
-class C_formatter:public flag_formatter
+class C_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -175,7 +175,7 @@ class C_formatter:public flag_formatter
 
 
 // Short MM/DD/YY date, equivalent to %m/%d/%y 08/23/01
-class D_formatter:public flag_formatter
+class D_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -185,7 +185,7 @@ class D_formatter:public flag_formatter
 
 
 // year - 4 digit
-class Y_formatter:public flag_formatter
+class Y_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -194,7 +194,7 @@ class Y_formatter:public flag_formatter
 };
 
 // month 1-12
-class m_formatter:public flag_formatter
+class m_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -203,7 +203,7 @@ class m_formatter:public flag_formatter
 };
 
 // day of month 1-31
-class d_formatter:public flag_formatter
+class d_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -212,7 +212,7 @@ class d_formatter:public flag_formatter
 };
 
 // hours in 24 format  0-23
-class H_formatter:public flag_formatter
+class H_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -221,7 +221,7 @@ class H_formatter:public flag_formatter
 };
 
 // hours in 12 format  1-12
-class I_formatter:public flag_formatter
+class I_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -230,7 +230,7 @@ class I_formatter:public flag_formatter
 };
 
 // minutes 0-59
-class M_formatter:public flag_formatter
+class M_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -239,7 +239,7 @@ class M_formatter:public flag_formatter
 };
 
 // seconds 0-59
-class S_formatter:public flag_formatter
+class S_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -248,7 +248,7 @@ class S_formatter:public flag_formatter
 };
 
 // milliseconds
-class e_formatter:public flag_formatter
+class e_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -259,7 +259,7 @@ class e_formatter:public flag_formatter
 };
 
 // microseconds
-class f_formatter:public flag_formatter
+class f_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -270,7 +270,7 @@ class f_formatter:public flag_formatter
 };
 
 // nanoseconds
-class F_formatter:public flag_formatter
+class F_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -281,7 +281,7 @@ class F_formatter:public flag_formatter
 };
 
 // AM/PM
-class p_formatter:public flag_formatter
+class p_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -291,7 +291,7 @@ class p_formatter:public flag_formatter
 
 
 // 12 hour clock 02:55:02 pm
-class r_formatter:public flag_formatter
+class r_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -300,7 +300,7 @@ class r_formatter:public flag_formatter
 };
 
 // 24-hour HH:MM time, equivalent to %H:%M
-class R_formatter:public flag_formatter
+class R_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -309,7 +309,7 @@ class R_formatter:public flag_formatter
 };
 
 // ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S
-class T_formatter:public flag_formatter
+class T_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
@@ -319,7 +319,7 @@ class T_formatter:public flag_formatter
 
 
 // ISO 8601 offset from UTC in timezone (+-HH:MM)
-class z_formatter:public flag_formatter
+class z_formatter SPDLOG_FINAL:public flag_formatter
 {
 public:
     const std::chrono::seconds cache_refresh = std::chrono::seconds(5);
@@ -376,7 +376,7 @@ private:
 
 
 // Thread id
-class t_formatter:public flag_formatter
+class t_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -385,7 +385,7 @@ class t_formatter:public flag_formatter
 };
 
 // Current pid
-class pid_formatter:public flag_formatter
+class pid_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -394,7 +394,7 @@ class pid_formatter:public flag_formatter
 };
 
 
-class v_formatter:public flag_formatter
+class v_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm&) override
     {
@@ -402,7 +402,7 @@ class v_formatter:public flag_formatter
     }
 };
 
-class ch_formatter:public flag_formatter
+class ch_formatter SPDLOG_FINAL:public flag_formatter
 {
 public:
     explicit ch_formatter(char ch): _ch(ch)
@@ -417,7 +417,7 @@ private:
 
 
 //aggregate user chars to display as is
-class aggregate_formatter:public flag_formatter
+class aggregate_formatter SPDLOG_FINAL:public flag_formatter
 {
 public:
     aggregate_formatter()
@@ -436,7 +436,7 @@ private:
 
 // Full info formatter
 // pattern: [%Y-%m-%d %H:%M:%S.%e] [%n] [%l] %v
-class full_formatter:public flag_formatter
+class full_formatter SPDLOG_FINAL:public flag_formatter
 {
     void format(details::log_msg& msg, const std::tm& tm_time) override
     {
diff --git a/include/spdlog/formatter.h b/include/spdlog/formatter.h
index 0ffcec03..639cc7d2 100644
--- a/include/spdlog/formatter.h
+++ b/include/spdlog/formatter.h
@@ -25,7 +25,7 @@ public:
     virtual void format(details::log_msg& msg) = 0;
 };
 
-class pattern_formatter : public formatter
+class pattern_formatter SPDLOG_FINAL : public formatter
 {
 
 public:
diff --git a/include/spdlog/sinks/ansicolor_sink.h b/include/spdlog/sinks/ansicolor_sink.h
index 96e10148..d9df4349 100644
--- a/include/spdlog/sinks/ansicolor_sink.h
+++ b/include/spdlog/sinks/ansicolor_sink.h
@@ -21,7 +21,7 @@ namespace sinks
  * the output with an ANSI escape sequence color code depending on the severity
  * of the message.
  */
-class ansicolor_sink : public sink
+class ansicolor_sink SPDLOG_FINAL : public sink
 {
 public:
     ansicolor_sink(sink_ptr wrapped_sink);
diff --git a/include/spdlog/sinks/base_sink.h b/include/spdlog/sinks/base_sink.h
index 0a539f32..c0a910e0 100644
--- a/include/spdlog/sinks/base_sink.h
+++ b/include/spdlog/sinks/base_sink.h
@@ -31,7 +31,7 @@ public:
     base_sink(const base_sink&) = delete;
     base_sink& operator=(const base_sink&) = delete;
 
-    void log(const details::log_msg& msg) override
+    void log(const details::log_msg& msg) SPDLOG_FINAL override
     {
         std::lock_guard<Mutex> lock(_mutex);
         _sink_it(msg);
diff --git a/include/spdlog/sinks/file_sinks.h b/include/spdlog/sinks/file_sinks.h
index 721a96df..fe40a362 100644
--- a/include/spdlog/sinks/file_sinks.h
+++ b/include/spdlog/sinks/file_sinks.h
@@ -26,7 +26,7 @@ namespace sinks
  * Trivial file sink with single file as target
  */
 template<class Mutex>
-class simple_file_sink : public base_sink < Mutex >
+class simple_file_sink SPDLOG_FINAL : public base_sink < Mutex >
 {
 public:
     explicit simple_file_sink(const filename_t &filename, bool truncate = false):_force_flush(false)
@@ -61,7 +61,7 @@ typedef simple_file_sink<details::null_mutex> simple_file_sink_st;
  * Rotating file sink based on size
  */
 template<class Mutex>
-class rotating_file_sink : public base_sink < Mutex >
+class rotating_file_sink SPDLOG_FINAL : public base_sink < Mutex >
 {
 public:
     rotating_file_sink(const filename_t &base_filename,
@@ -177,7 +177,7 @@ struct dateonly_daily_file_name_calculator
  * Rotating file sink based on date. rotates at midnight
  */
 template<class Mutex, class FileNameCalc = default_daily_file_name_calculator>
-class daily_file_sink :public base_sink < Mutex >
+class daily_file_sink SPDLOG_FINAL :public base_sink < Mutex >
 {
 public:
     //create daily file sink which rotates on given time
diff --git a/include/spdlog/sinks/stdout_sinks.h b/include/spdlog/sinks/stdout_sinks.h
index c05f80dd..4dd52ed8 100644
--- a/include/spdlog/sinks/stdout_sinks.h
+++ b/include/spdlog/sinks/stdout_sinks.h
@@ -18,7 +18,7 @@ namespace sinks
 {
 
 template <class Mutex>
-class stdout_sink: public base_sink<Mutex>
+class stdout_sink SPDLOG_FINAL : public base_sink<Mutex>
 {
     using MyType = stdout_sink<Mutex>;
 public:
@@ -47,7 +47,7 @@ typedef stdout_sink<std::mutex> stdout_sink_mt;
 
 
 template <class Mutex>
-class stderr_sink: public base_sink<Mutex>
+class stderr_sink SPDLOG_FINAL : public base_sink<Mutex>
 {
     using MyType = stderr_sink<Mutex>;
 public: