Remove crashy unwrap() in on_error

[emilk]

I got a crash here, and I don't want a crash :)

thread 'av1_decoder' panicked at 'called `Option::unwrap()` on a `None` value'
6f12e3f/src/decode.rs:4997

It seems like this unwrap was introduced in #663 along with many others.

May I suggest enabling the clippy::unwrap_used lint? Any .unwrap() is a panic waiting to happen :/

EDIT: The crash happens during decode of the chunk starting at timestamp 114176 of this video: https://storage.googleapis.com/rerun-test-assets/video/Sintel_1080_10s_av1.mp4

[emilk]

I'm not sure what the right behavior is in the None case, but crashing is certainly not it

[kkysen]

Places where there is an unwrap should have been unchecked derefs in C, so let me check what C was doing here.

[kkysen]

So C is doing the same thing as we are here:

• rav1d/src/decode.c

  Line 3350 in c7d127e

  if (f->frame_hdr->refresh_context)

• https://code.videolan.org/videolan/dav1d/-/blob/master/src/decode.c?ref_type=heads#L3722

Can you check if you get an error/crash on dav1d here or not? Thanks!

[emilk]

Using https://crates.io/crates/dav1d 0.10.3 I do not get a crash, but I get an Invalid argument error and some useful info printed:

Error parsing frame header
Error parsing OBU data

It should be noted though that dereferencing a null pointer is not necessarily a crash in C - it is Undefined Behavior. The compiler is free to assume the pointer is not null, and do whatever crazy shenanigans that implies.

[kkysen]

Hmm, it's possible UB could be doing something weird here, but I'd still expect a segfault for the most part. We likely diverged at some point, so we'll have to figure out where and see if that's something we need to fix or if it's okay to crash, just in a different place.

That said, this video should successfully decode with normal dav1d, but doesn't? Is that a bug with dav1d as well?

[emilk]

or if it's okay to crash

I would prefer a rav1d that never crashes on any input, but returns errors.

That said, this video should successfully decode with normal dav1d, but doesn't? Is that a bug with dav1d as well?

I don't know if the video should successfully decode, or if it is actually a bad video.

[kkysen]

I would prefer a rav1d that never crashes on any input, but returns errors.

Yup, that would definitely be preferable.

[kkysen]

What input were you running this on?

[emilk]

I was running this video (the crash happens about half-way through it):

https://storage.googleapis.com/rerun-test-assets/video/Sintel_1080_10s_av1.mp4

The crash happens during decode of the chunk starting at timestamp 114176

[kkysen]

Hi @emilk, I have some time to look into this bug now. What specific command did you use on Sintel_1080_10s_av1.mp4 that triggered the bug? Sorry, I'm not super familiar with all of the CLI options besides what's run in the tests.