Thanks for your reply.
In last mail, I have mentioned ldap API's used in my code. After all API call, am checking the return value. If it is success, then only am going for next api call, otherwise I will return from that point.
In that crash scenario, ldap_start_tls_s() returned LDAP_SUCCESS, but it crashed inside
That is why, I suspected ldap_start_tls_s() has corrupted the handle.