BUG#43949 Initialization of slave produces a warning message in Valgrind

In order to define the --slave-load-tmpdir, the init_relay_log_file()
was calling fn_format(MY_PACK_FILENAME) which internally was indirectly
calling strmov_overlapp() (through pack_dirname) and the following
warning message was being printed out while running in Valgrind:
"source and destination overlap in strcpy".

We fixed the issue by removing the flag MY_PACK_FILENAME as it was not
necessary. In a nutshell, with this flag the function fn_format() tried
to replace a directory by either "~", "." or "..". However, we wanted
exactly to remove such strings.

In this patch, we also refactored the functions init_relay_log_file()
and check_temp_dir(). The former was refactored to call the fn_format()
with the flag MY_SAFE_PATH along with the MY_RETURN_REAL_PATH,  in order
to avoid issues with long directories and return an absolute path,
respectively. The flag MY_SAFE_UNPACK_FILENAME was removed too as it was
responsible for removing "~", "." or ".." only from the file parameter
and we wanted to remove such strings from the directory parameter in
the fn_format(). This result is stored in an rli variable, which is then
processed by the other function in order to verify if the directory exists
and if we are able to create files in it.


mysql-test/suite/rpl/t/rpl_slave_load_tmpdir_not_exist.test:
  Changed the output to make it consistent among different runs.
mysys/mf_format.c:
  Replaced a return for DBUG_RETURN.

mysql-test/suite/rpl/r/rpl_slave_load_tmpdir_not_exist.result

@@ -3,4 +3,4 @@ MASTER_CONNECT_RETRY=1,
 MASTER_HOST='127.0.0.1',
 MASTER_PORT=MASTER_MYPORT;
 START SLAVE;
-Unable to use slave's temporary directory ../../../error - Can't read dir of '../../../error' (Errcode: 2)
+12

mysql-test/suite/rpl/t/rpl_slave_load_tmpdir_not_exist.test

@@ -20,5 +20,5 @@ eval CHANGE MASTER TO MASTER_USER='root',
 START SLAVE;
 
 source include/wait_for_slave_sql_to_stop.inc;
-let $error=query_get_value("show slave status", Last_SQL_Error, 1);
-echo $error;
+let $errno=query_get_value("show slave status", Last_SQL_Errno, 1);
+echo $errno;

mysys/mf_format.c

@@ -79,7 +79,7 @@ char * fn_format(char * to, const char *name, const char *dir,
     /* To long path, return original or NULL */
     size_t tmp_length;
     if (flag & MY_SAFE_PATH)
-      return NullS;
+      DBUG_RETURN(NullS);
     tmp_length= strlength(startpos);
     DBUG_PRINT("error",("dev: '%s'  ext: '%s'  length: %u",dev,ext,
                         (uint) length));

sql/rpl_rli.cc

@@ -104,9 +104,16 @@ int init_relay_log_info(Relay_log_info* rli,
   rli->tables_to_lock= 0;
   rli->tables_to_lock_count= 0;
 
-  fn_format(rli->slave_patternload_file, PREFIX_SQL_LOAD, slave_load_tmpdir, "",
-            MY_PACK_FILENAME | MY_UNPACK_FILENAME |
-            MY_RETURN_REAL_PATH);
+  char pattern[FN_REFLEN];
+  if (fn_format(pattern, PREFIX_SQL_LOAD, slave_load_tmpdir, "",
+            MY_SAFE_PATH | MY_RETURN_REAL_PATH) == NullS)
+  {
+    pthread_mutex_unlock(&rli->data_lock);
+    sql_print_error("Unable to use slave's temporary directory %s",
+                    slave_load_tmpdir);
+    DBUG_RETURN(1);
+  }
+  unpack_filename(rli->slave_patternload_file, pattern);
   rli->slave_patternload_file_size= strlen(rli->slave_patternload_file);
 
   /*

sql/slave.cc

@@ -2648,13 +2648,20 @@ err:
   LOAD DATA INFILE.
  */
 static 
-int check_temp_dir(char* tmp_dir, char *tmp_file)
+int check_temp_dir(char* tmp_file)
 {
   int fd;
   MY_DIR *dirp;
+  char tmp_dir[FN_REFLEN];
+  size_t tmp_dir_size;
 
   DBUG_ENTER("check_temp_dir");
 
+  /*
+    Get the directory from the temporary file.
+  */
+  dirname_part(tmp_dir, tmp_file, &tmp_dir_size);
+
   /*
     Check if the directory exists.
    */
@@ -2810,7 +2817,7 @@ log '%s' at position %s, relay log '%s' position: %s", RPL_LOG_NAME,
                     llstr(rli->group_master_log_pos,llbuff),rli->group_relay_log_name,
                     llstr(rli->group_relay_log_pos,llbuff1));
 
-  if (check_temp_dir(slave_load_tmpdir, rli->slave_patternload_file))
+  if (check_temp_dir(rli->slave_patternload_file))
   {
     rli->report(ERROR_LEVEL, thd->main_da.sql_errno(), 
                 "Unable to use slave's temporary directory %s - %s",