Comment 2 for bug 1009118

Thanks for the report, I can reproduce this. However, from the stack trace I get, it seems to be a bug in libxml2:

#0 xmlXPathNormalizeFunction__internal_alias (ctxt=0x929940, nargs=<optimized out>) at xpath.c:9252
#1 xmlXPathNormalizeFunction__internal_alias (ctxt=0x929940, nargs=<optimized out>) at xpath.c:9233
#2 0x00007ffff57c59e2 in xmlXPathCompOpEval (ctxt=0x929940, op=0xa93600) at xpath.c:13490
#3 0x00007ffff57c4dc2 in xmlXPathCompOpEval (op=<optimized out>, ctxt=0x929940) at xpath.c:13190
#4 xmlXPathCompOpEval (ctxt=0x929940, op=0xa93640) at xpath.c:13874
#5 0x00007ffff57c582f in xmlXPathCompOpEval (ctxt=0x929940, op=0xa93680) at xpath.c:13508
#6 0x00007ffff57c57dd in xmlXPathCompOpEval (op=<optimized out>, ctxt=0x929940) at xpath.c:13190
#7 xmlXPathCompOpEval (ctxt=0x929940, op=0xa93700) at xpath.c:13502
#8 0x00007ffff57c5950 in xmlXPathCompOpEval (op=<optimized out>, ctxt=0x929940) at xpath.c:13190
#9 xmlXPathCompOpEval (ctxt=0x929940, op=0xa93740) at xpath.c:13438
#10 0x00007ffff57c51ea in xmlXPathCompOpEval (op=<optimized out>, ctxt=<optimized out>) at xpath.c:13190
#11 xmlXPathCompOpEval (ctxt=0x929940, op=0xa937c0) at xpath.c:13252
#12 0x00007ffff57c6f5f in xmlXPathCompOpEval (op=0xa937c0, ctxt=0x929940) at xpath.c:13190
#13 xmlXPathCompOpEvalToBoolean (ctxt=0x929940, op=<optimized out>, isPredicate=1) at xpath.c:14108
#14 0x00007ffff57c79d1 in xmlXPathCompOpEvalPredicate (ctxt=0x929940, set=<optimized out>, contextSize=1, hasNsNodes=0, op=<optimized out>) at xpath.c:11664
#15 0x00007ffff57c8af5 in xmlXPathNodeCollectAndTest (ctxt=0x929940, op=<optimized out>, first=<optimized out>, last=<optimized out>, toBool=0) at xpath.c:12520
#16 0x00007ffff57c5698 in xmlXPathCompOpEval (ctxt=0x929940, op=0xa93840) at xpath.c:13387
#17 0x00007ffff57c4dc2 in xmlXPathCompOpEval (op=<optimized out>, ctxt=0x929940) at xpath.c:13190
#18 xmlXPathCompOpEval (ctxt=0x929940, op=0xa93880) at xpath.c:13874
#19 0x00007ffff57c70c8 in xmlXPathCompOpEval (op=<optimized out>, ctxt=0x929940) at xpath.c:13190
#20 xmlXPathRunEval (ctxt=0x929940, toBool=0) at xpath.c:14444
#21 0x00007ffff57ce674 in xmlXPathEvalExpression__internal_alias (str=<optimized out>, ctxt=0xa901a0) at xpath.c:15019
#22 0x00007ffff5fc6bb7 in __pyx_pw_4lxml_5etree_21XPathElementEvaluator_7__call__ () from /home/sbehnel/source/Python/lxml/lxml-hg/src/lxml/etree.so

I don't see how lxml can handle this.