libc by itself provides a Turing-complete set of ROP gadgets:
<http://www.cs.ncsu.edu/faculty/jiang/pubs/RAID11.pdf>.
Second of all: ugh! Dear HackerNews team, please fix your URL matching algorithm so it doesn't include <> in URLs; they're actually explicitly recommended by the URI RFC as delimiters.
Sincerely,
halosghost
The other paper shows that this technique is Turing complete.
But yes, basically W^X is defeated.