Fix incorrect string length calculation.

Closes #1963. Thanks to twegener-embertec.

man/mosquitto.conf.5.xml

@@ -824,8 +824,7 @@ log_timestamp_format %Y-%m-%dT%H:%M:%S
 				<term><option>persistence_location</option> <replaceable>path</replaceable></term>
 				<listitem>
 					<para>The path where the persistence database should be
-						stored. Must end in a trailing slash. If not given,
-						then the current directory is used.</para>
+						stored. If not given, then the current directory is used.</para>
 
 					<para>This option applies globally.</para>
 

mosquitto.conf

@@ -412,9 +412,9 @@
 # the path.
 #persistence_file mosquitto.db
 
-# Location for persistent database. Must include trailing /
+# Location for persistent database.
 # Default is an empty string (current directory).
-# Set to e.g. /var/lib/mosquitto/ if running as a proper service on Linux or
+# Set to e.g. /var/lib/mosquitto if running as a proper service on Linux or
 # similar.
 #persistence_location
 

src/conf.c

@@ -661,7 +661,7 @@ int config__read(struct mosquitto__config *config, bool reload)
 		}
 		mosquitto__free(config->persistence_filepath);
 		if(config->persistence_location && strlen(config->persistence_location)){
-			len = strlen(config->persistence_location) + strlen(config->persistence_file) + 1;
+			len = strlen(config->persistence_location) + strlen(config->persistence_file) + 2;
 			config->persistence_filepath = mosquitto__malloc(len);
 			if(!config->persistence_filepath) return MOSQ_ERR_NOMEM;
 #ifdef WIN32