Support for arbitrary data types

[nagisa]

Not efficient[1], but that mostly needs work on the arbitrary crate, as opposed to work on libfuzzer-sys.

[1]: fuzzing struggles with e.g.

fuzz_target!(|data: String| { if data == "banana" { panic!() } });

and takes quite a while to find an input that fails the check (compared to fuzzing against raw bytes). It seems to me that to take full advantage of fuzzing structured data, one would have to adjust libFuzzer somehow or, perhaps, rewrite libFuzzer in rust having precisely structured fuzzing in mind.

[nagisa]

cc @Manishearth @frewsxcv for a review.

[Manishearth]

Why not just use the quickcheck stuff here? Bonus points if we can make a macro that also expands to a quickcheck test depending on some flag.

[nagisa]

Primary motivation is me not really wanting to deal with having to land stuff into quickcheck at the moment, because I need fast turn-around times for upcoming month.

Besides, quickcheck’s implementations of arbitrary are oriented towards quickcheck and random data, and those don’t necessarily work well for generating structured data from, say, a ring buffer as is done here.

In the end, I hope to migrate quickcheck itself to use the arbitrary crate, but it might end up being entirely unfeasible due to significantly differing requirements/desires/constraints.

[Manishearth]

@burntsushi thoughts?

fine with merging as is but would like to avoid duplication

[BurntSushi]

@Manishearth I don't have any specific thoughts, but I am strongly in favor of folks experimenting with improving quickcheck-style testing. Not everything in this realm fits cleanly with how the quickcheck crate is setup, and I suspect there are nice ergonomic wins to be had if the idea was given a refresh. (I might perhaps point folks towards auto-shrinking and the Hypothesis work.)

[Manishearth]

Cool. I'd love for the two crates to converge on a preferred solution eventually.

So r=me on this for now, looks ok otherwise.

[Manishearth]

bors: r+

[frewsxcv]

I finally got around to looking at this. This is very cool, thanks for doing this @nagisa :100: