[Xcb] Assert in xcb_io.c:542

[Graeme Gill]

Hi,
	a user of one of my applications is reporting an assert
from xcb:

% dispcal -v -q l -y l test
dispcal: ../../src/xcb_io.c:542: _XRead: Assertion
`dpy->xcb->reply_data != ((void *)0)' failed.
zsh: abort (core dumped)  dispcal -v -q l -y l test

This application has been running fine for a long time
with the non xcb based client libraries.

Is this likely to be a bug in xcb, or some sort of
latent bug in corresponding application X11 call
that the original X11 client libraries didn't trip
up on ? What further information is needed to track
this down ?

thanks,
	Graeme Gill.