How do you deal with structured formats, like XML? In JQF you would just write a XML generator (see their examples). If you just use the "sequence of bytes" approach as AFL does, then a lot of your inputs might be immediately rejected by the parser.

The FuzzedDataProvider (docs at https://codeintelligencetesting.github.io/jazzer-api/com/cod...) offers many of the functions you would need to write such a generator. If there is something missing that could be generally useful, we can always add it.

We use our internal grammar generator similar to libprotobuf mutator. For the OSS solution, we recommend to use libprotobuf mutator though. The reason to abstract this is that we don't want to write the grammars for a single programming language only.