Augmentation moved.

Augmentation moved to skygw_log_write_context. The severity prefix
will be added there as well. If all is done on that level, the
amount of memory needed can be figured out in one go. No need to
allocate and copy the message several times.

log_manager/log_manager.cc

@@ -1468,42 +1468,6 @@ static int log_write(logfile_id_t   id,
     {
         CHK_LOGMANAGER(lm);
 
-        const char* format;
-
-        if (log_augmentation == LOG_AUGMENT_WITH_FUNCTION)
-        {
-            static const char function_format[] = "%s [%s]";
-
-            format = function_format;
-
-            len += sizeof(function_format); // A little bit more than needed, but won't hurt.
-            assert(function);
-            len += strlen(function);
-        }
-        else
-        {
-            static const char default_format[] = "%s";
-
-            format = default_format;
-
-            len += sizeof(default_format);  // A little bit more than needed, but won't hurt.
-        }
-
-        len += 1; // For the trailing NULL.
-
-        char message[len];
-
-        if (log_augmentation == LOG_AUGMENT_WITH_FUNCTION)
-        {
-            len = snprintf(message, sizeof(message), format, str, function);
-        }
-        else
-        {
-            len = snprintf(message, sizeof(message), format, str);
-        }
-
-        assert(len >= 0);
-
         int attempts = 0;
         int successes = 0;
 
@@ -1529,7 +1493,7 @@ static int log_write(logfile_id_t   id,
                                          LOG_USE_VALIST_NO,
                                          LOG_SPREAD_DOWN_YES,
                                          LOG_ROTATE_NO,
-                                         len, message, valist) == 0)
+                                         len, str, valist) == 0)
                 {
                     ++successes;
                 }
@@ -1567,23 +1531,63 @@ int skygw_log_write_context(logfile_id_t   id,
      * Find out the length of log string (to be formatted str).
      */
     va_start(valist, str);
-    int len = vsnprintf(NULL, 0, str, valist);
+    int message_len = vsnprintf(NULL, 0, str, valist);
     va_end(valist);
 
-    if (len >= 0)
+    if (message_len >= 0)
     {
-        if (len > MAX_LOGSTRLEN)
+        static const char FORMAT_FUNCTION[] = "(%s): ";
+
+        int augmentation_len = 0;
+
+        switch (log_augmentation)
         {
-            len = MAX_LOGSTRLEN;
+        case LOG_AUGMENT_WITH_FUNCTION:
+            augmentation_len = sizeof(FORMAT_FUNCTION) - 1; // Remove trailing 0
+            augmentation_len -= 2; // Remove the %s
+            augmentation_len += strlen(function);
+            break;
+
+        default:
+            break;
         }
 
-        char message[len + 1];
+        int buffer_len = augmentation_len + message_len + 1; // Trailing NULL
+
+        if (buffer_len > MAX_LOGSTRLEN)
+        {
+            message_len -= (buffer_len - MAX_LOGSTRLEN);
+            buffer_len = MAX_LOGSTRLEN;
+
+            assert(augmentation_len + message_len + 1 == buffer_len);
+        }
+
+        char buffer[buffer_len];
+        char *message = buffer + augmentation_len;
+
+        if (augmentation_len)
+        {
+            char *augmentation = buffer;
+            int len = 0;
+
+            switch (log_augmentation)
+            {
+            case LOG_AUGMENT_WITH_FUNCTION:
+                len = sprintf(augmentation, FORMAT_FUNCTION, function);
+                break;
+
+            default:
+                assert(!true);
+            }
+
+            assert(len == augmentation_len);
+        }
 
         va_start(valist, str);
-        vsnprintf(message, sizeof(message), str, valist);
+        vsnprintf(message, message_len + 1, str, valist);
         va_end(valist);
 
-        err = log_write(id, file, line, function, len, message, flush);
+        err = log_write(id, file, line, function, buffer_len - 1, buffer, flush);
 
         if (err != 0)
         {