Multi value! And even more fuzzing! #124
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It looks like some change here (probably related to blocks having types or making the types shared) is making the types come out in non-deterministic orders. I'm going to solve this with an explicit sorting step for emitting types. |
alexcrichton
reviewed
Sep 3, 2019
Nice! Mind running a few benchmarks to ensure that the usage of Mutex/Arc don't regress our current parsing performance?
I'm also curious, could you explain a bit more where the need for interior mutability arose?
Instead of holding a couple of `Box<[ValType]>`s for parameters and results, now they more accurately reflect the spec (and the multi-value extension of it). For simple, MVP wasm, they hold the optional return value type directly inline. For multi-value, they reference a `TypeId`. See the `NB` comment above `InstrSeqType` for details about why this split is beneficial, and we shouldn't *only* use `TypeId`.
This commit adds support for parsing, emitting, and manipulating multi-value Wasm!
This will let us define custom RNGs that are controlled via libFuzzer and/or AFL, so that we can get coverage-guided fuzzing instead of purely random fuzzing.
Re-uses basically all of our existing fuzzing infrastructure, but uses libfuzzer to drive the "RNG" values that we generate Wat with. This lets us combine the benefits of coverage-guided fuzzing with our existing "structured" fuzzing.
This is not /strictly/ necessary because they are otherwise emitted in the order that they are added, which is usually the order that they are parsed. However, if one were adding types in a non-deterministic order, then we would emit types non-deterministically. Overall, this is just a nice robustness addition.
And so its signature should reflect that.
alexcrichton
approved these changes
Sep 5, 2019
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fixes #77