xcb_send_event() reads beyond end of argument / is hard to use correctly
Submitted by Uli Schlachter @psychon
Assigned to xcb mailing list dummy
Description
https://bugreports.qt.io/browse/QTBUG-56518 is about valgrind warnings that occur in Qt. The code in question does basically:
xcb_unmap_notify_event_t event;
set all fields of event;
xcb_send_event(c, false, root, mask, &event);The problem here is that sizeof(event) is 16 while xcb_send_event() expects 32 bytes of event data. So the argument needs to be "something bigger". This is quite unintuitive and it seems like everyone using xcb_send_event() is getting this wrong. (I would claim that I know may way around XCB and I did not know this!)
Can there be a version of xcb_send_event() which gets a length argument? Are there any other ideas on how this could be made safer or more obvious?