Dear Maintainer,

  it is not possible to use X server as XDMCP client. Running:
root@Terminal:~# X -query <server>
.... leads to crash during session initialization.

<server> is properly set workstation with working XDMCP protocol.

Looking to problem I'll find that there is announced WARNING (BUG_WARN_MSG)
in function vpnprintf in log.c, but later it is evaluated as fatal error.

My suggestion:
This problem occurs when character sequence "%*" occurs in input string,
where "*" is any character not known as print directive.
I think it can be solved sending "%%*" sequence to output string.

Regards,
  Pavel