MDEV-20377: Fix uninitialized memory in mysqltest

client/mysqltest.cc

 /* Copyright (c) 2000, 2013, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2017, MariaDB
+   Copyright (c) 2009, 2019, MariaDB
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1693,6 +1693,7 @@ void abort_not_supported_test(const char *fmt, ...)
           cur_file->file_name, cur_file->lineno);
 
   char buff[DIE_BUFF_SIZE];
+  buff[0] = '\0';
   print_file_stack(buff, buff + sizeof(buff));
   fprintf(stderr, "%s", buff);
 

mysql-test/lib/My/SafeProcess/safe_process.cc

 /* Copyright (c) 2008, 2012, Oracle and/or its affiliates
+   Copyright (c) 2019, MariaDB Corporation.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -169,6 +170,7 @@ int main(int argc, char* const argv[] )
   sigemptyset(&sa.sa_mask);
 
   sa_abort.sa_handler= handle_abort;
+  sa_abort.sa_flags= 0;
   sigemptyset(&sa_abort.sa_mask);
   /* Install signal handlers */
   sigaction(SIGTERM, &sa,NULL);