How to add custom metadata for solution?

[Slava0135]

I have a differential fuzzer that reads output from stdout and compares it.
I want to save the stdout in metadata so I can check the output of programs without rerunning them, but unable to figure out how to do so.

[domenukk]

You can eager_or an extra ToMetadata feedback that will do nothing but append metadata. Specifically, this one: StdOutToMetadataFeedback

LibAFL/libafl/src/feedbacks/stdio.rs

Line 107 in 4e54182

impl StdOutToMetadataFeedback {

(Using feedback_or!)

[Slava0135]

I decided save data to Feedback struct and then use it in append_metadata, maybe this should be put in function description (unless this is not intentional way of doing things). I first thought it wouldn't be called for solution (only for corpus).

[domenukk]

It's not perfect but it's the way we do it right now.
Feel free to open a PR to add documentation for clarification :)