Init files for fuzzing

[darrenldl]

Spawned from #338

Adds the following fuzzing tests:

• ccsexp_parse_string_does_not_crash
  • The fuzzing test that revealed CCSexp.parse_string crash/unexpected Invalid_argument exception #338
• ccutf8_string_uchar_to_bytes_is_same_as_simple_version
  • Tests CCUtf8_string.uchar_to_bytes against a simpler implementation of the equivalent

[c-cube]

I get this after trying to call run.sh:

[-] Hmm, looks like the target binary terminated before we could complete a
    handshake with the injected code. There are two probable explanations:

    - The current memory limit (50.0 MB) is too restrictive, causing an OOM
      fault in the dynamic linker. This can be fixed with the -m option. A
      simple way to confirm the diagnosis may be:

      ( ulimit -Sv $[49 << 10]; /path/to/fuzzed_app )

      Tip: you can use http://jwilk.net/software/recidivm to quickly
      estimate the required amount of virtual memory for the binary.

    - Less likely, there is a horrible bug in the fuzzer. If other options
      fail, poke <lcamtuf@coredump.cx> for troubleshooting tips.

[darrenldl]

Is that with both tests? Both run fine on my system : /

[darrenldl]

I've increased the virtual memory allocated to 100MiB, but I'm not confident that's the issue.

[darrenldl]

Aha, I managed to replicate that when I'm back to switch 4.08.1 instead of 4.08.1+afl - were you using a +afl switch when running the scripts?

[c-cube]

I'm using 4.11.1+afl, but maybe there's some opam state that has not been properly updated when I upgraded my switch.

[darrenldl]

Both tests still run fine for me after switching to 4.11.1+afl, hm...

[c-cube]

It was my fault, sorry. I thought I had 4.11.1+afl, but it turns out opam had rejected my pin (I needed opam pin ocaml-variants 4.11.1+afl --unlock-base) so I had a vanilla 4.11.

This seems to work, it's fuzzing right now!! 😁