add MSG_ONCE

refer to GH-411

Author: MartinPulec

src/debug.cpp

@@ -134,6 +134,12 @@ void log_msg(int level, const char *format, ...) {
         va_end(ap);
 }
 
+/**
+ * @param  id  the identifier that idetifies identical messages (only first
+ * message of given ID is printed); use values < 0x8000'0000 for manually
+ * generated IDs, the higher values are reserved for automatically generated
+ * ones as in MSG_ONCE()
+ */
 void log_msg_once(int level, uint32_t id, const char *msg, ...) {
         if (log_level < level) {
                 return;

src/debug.h

@@ -96,6 +96,12 @@ void log_perror(int log_level, const char *msg);
 #define MSG(l, fmt, ...) \
         if (log_level >= LOG_LEVEL_##l) \
                 log_msg(LOG_LEVEL_##l, "%s" fmt, MOD_NAME, ##__VA_ARGS__)
+#define MSG_ONCE(l, fmt, ...) \
+        if (log_level >= LOG_LEVEL_##l) \
+                log_msg_once(LOG_LEVEL_##l, \
+                             (0x80000000U | (((uintptr_t) MOD_NAME) & \
+                                 0x7FFFFFFF)) +  __COUNTER__, \
+                             "%s" fmt, MOD_NAME, ##__VA_ARGS__)
 
 bool parse_log_cfg(const char *conf_str,
 		int *log_lvl,