merge (and including the fix for bug#48939 since that was not included in mysql-trunk-bugfixing).

mysql-test/include/check_key_reads.inc

+# include file for checking if variable key_reads is zero
+let $key_reads= query_get_value(SHOW STATUS LIKE 'key_reads',Value,1);
+--disable_query_log
+eval SELECT IF($key_reads = 0, "Yes!", "No!") as 'Zero key reads?';
+FLUSH STATUS;
+--enable_query_log

mysql-test/include/check_key_req.inc

+# include file for checking if variable key_reads = key_read_requests
+let $key_reads= query_get_value(SHOW STATUS LIKE 'key_reads',Value,1);
+let $key_r_req= query_get_value(SHOW STATUS LIKE 'key_read_requests',Value,1);
+let $key_writes= query_get_value(SHOW STATUS LIKE 'key_writes',Value,1);
+let $key_w_req= query_get_value(SHOW STATUS LIKE 'key_write_requests',Value,1);
+--disable_query_log
+eval SELECT IF($key_reads = $key_r_req, "reads == requests", "reads != requests") as 'reads vs requests';
+eval SELECT IF($key_writes = $key_w_req, "writes == requests", "writes != requests") as 'writes vs requests';
+--enable_query_log

sql/protocol.cc

@@ -411,8 +411,8 @@ bool net_send_error_packet(THD *thd, uint sql_errno, const char *err,
                                            thd->variables.character_set_results,
                                            err, strlen(err),
                                            system_charset_info, &error);
-  length= (uint) (strmake((char*) pos, (char*)converted_err, MYSQL_ERRMSG_SIZE) -
-                  (char*) buff);
+  length= (uint) (strmake((char*) pos, (char*)converted_err,
+                          MYSQL_ERRMSG_SIZE - 1) - (char*) buff);
   err= (char*) buff;
   DBUG_RETURN(net_write_command(net,(uchar) 255, (uchar*) "", 0, (uchar*) err,
                                 length));