14 releases

0.4.5 Apr 19, 2019
0.4.4 Mar 15, 2019
0.4.3 Jan 3, 2019
0.4.2 Nov 15, 2018
0.1.1 Mar 24, 2018

#15 in WebAssembly

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Used in 4 crates (3 directly)


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wasmi - a Wasm interpreter.

wasmi was conceived as a component of parity-ethereum (ethereum-like contracts in wasm) and substrate. These projects are related to blockchain and require a high degree of correctness, even if that might be over conservative. This specifically means that we are not trying to be involved in any implementation of any of work-in-progress Wasm proposals. We are also trying to be as close as possible to the spec, which means we are trying to avoid features that is not directly supported by the spec. This means that it is flexible on the one hand and on the other hand there shouldn't be a problem migrating to another spec compilant execution engine.

With all that said, wasmi should be a good option for initial prototyping.

Build & Test

As wasmi contains a git submodule, you need to use --recursive for cloning or to checkout the submodule explicitly, otherwise the testing would fail.

git clone https://github.com/paritytech/wasmi.git --recursive
cd wasmi
cargo build
cargo test

no_std support

This crate supports no_std environments. Enable the core feature and disable default features:

parity-wasm = {
	version = "0.31",
	default-features = false,
	features = "core"

The core feature requires the core and alloc libraries and a nightly compiler. Also, code related to std::error is disabled.

Floating point operations in no_std use libm, which sometimes panics in debug mode (https://github.com/japaric/libm/issues/4). So make sure to either use release builds or avoid WASM with floating point operations, for example by using deny_floating_point.


wasmi is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), at your choice.

See LICENSE-APACHE, and LICENSE-MIT for details.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in wasmi by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


~13K SLoC