[Xcb] bug #7261: random crashes with Xlib/XCB

Jamey Sharp jamey at minilop.net
Wed Sep 13 01:13:13 PDT 2006

On Wed, Sep 13, 2006 at 03:41:49AM +0200, morgoth6 at box43.pl wrote:
> Hmm, what about #7261 ? It was reported quite long time ago, but there
> is still no news about possible sollution. Generaly I give a try to
> XCB && libX11 maybe week or two ago, but the problem is still there.
> No sure is it libxcb or libX11 related, but maybe someone would take a
> look.

Oops, I never got around to looking at the ethereal logs I asked for.

I really need sleep right now, but on quick glance through the ethereal
log it looks like an assumption I made in xcb/src/xcb_in.c was wrong:

if(genrep.response_type != XCBReply) /* error or event */
	c->in.request_completed = c->in.request_read;
	/* XXX: does event/error imply no more replies? */

In the trace where things fail, you're getting an event with sequence
number 1474 immediately before getting a reply with the same sequence
number. I think that'll incorrectly trigger the above code.

In conclusion, probably this is an XCB implementation bug. I'll look at
it when I'm more awake. I guess it wouldn't actually block the release,
though, because fixing it shouldn't require API or ABI changes.

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