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We only generate *valid* sequences of API calls. To do this, we keep track of what objects we've already created in earlier API calls via the `Scope` struct. To generate even-more-pathological sequences of API calls, we use [swarm testing]: > In swarm testing, the usual practice of potentially including all features > in every test case is abandoned. Rather, a large “swarm” of randomly > generated configurations, each of which omits some features, is used, with > configurations receiving equal resources. [swarm testing]: https://www.cs.utah.edu/~regehr/papers/swarm12.pdf There are more public APIs and instance introspection APIs that we have than this fuzzer exercises right now. We will need a better generator of valid Wasm than `wasm-opt -ttf` to really get the most out of those currently-unexercised APIs, since the Wasm modules generated by `wasm-opt -ttf` don't import and export a huge variety of things.
Wasmtime: a WebAssembly Runtime
A Bytecode Alliance project
Wasmtime is a standalone wasm-only optimizing runtime for WebAssembly and WASI. It runs WebAssembly code outside of the Web, and can be used both as a command-line utility or as a library embedded in a larger application.
To get started, visit wasmtime.dev.
There are Rust, C, and C++ toolchains that can compile programs with WASI. See the WASI intro for more information, and the WASI tutorial for a tutorial on compiling and running programs using WASI and wasmtime, as well as an overview of the filesystem sandboxing system.
Wasmtime passes the WebAssembly spec testsuite. To run it, update the
tests/spec_testsuite submodule with git submodule update --remote, and it
will be run as part of cargo test.
Wasmtime does not yet implement Spectre mitigations, however this is a subject of ongoing research.
Additional goals for Wasmtime include:
- Support a variety of host APIs (not just WASI), with fast calling sequences, and develop proposals for additional API modules to be part of WASI.
- Facilitate development and testing around the Cranelift and Lightbeam JITs, and other WebAssembly execution strategies.
- Develop a native ABI used for compiling WebAssembly suitable for use in both JIT and AOT to native object files.
Including Wasmtime in your project
Wasmtime exposes an API for embedding as a library through the wasmtime subcrate,
which contains both a high-level and safe Rust API, as well as a C-compatible API
compatible with the proposed WebAssembly C API.
For more information, see the Rust API embedding chapter of the Wasmtime documentation.
It's Wasmtime.