A backdoor in xz

Yeah, solving this is hard.

In a similar area, for a long time we tried to make the libctf and ld.ctf testsuites in binutils work the same way the DWARF ones mostly do: describe a binary CTF dict via a .S file and just assemble it. But a mixture of there being no cross-arch-portable way to represent arbitrary binary data in .S files (.long, .byte4 etc, are all arch-dependent) and a desire to always test the latest CTF format except in a few error cases meant that nearly all of the tests end up compiling a .c file with -gctf just to get its CTF, then running the tests on that. It turned out to be much nicer to work with that, and much easier to see what the tests were actually *doing* as well: .S files are a pretty opaque way to describe a test input! (For corrupted CTF tests, the same problem arises, though at only a few dozen bytes each they're hardly likely to be malicious. There's just no room.)