XAllocID issues -- returns 0, calls geteuid, looks strange

[Younes Manton]

Ok, so

printf("%u\n", XAllocID(dpy));
printf("%u\n", XAllocID(dpy));

gives me

58720257
0

and no XFlush(), XSync(), XFlushGC() between the two changes that. I'm
using XAllocIDs() instead which seems to work properly, but is this
expected behaviour for XAllocID()?