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wasmvm

This is a wrapper around the CosmWasm VM. It allows you to compile, initialize and execute CosmWasm smart contracts from Go applications, in particular from x/wasm.

More information on what is CosmWasm and how to use it can be found here: CosmWasm Docs. To generate and show the Rust part documentation you can run make doc-rust.

Structure

This repo contains both Rust and Go code. The Rust code is compiled into a library (shared .dll/.dylib/.so or static .a) to be linked via cgo and wrapped with a pleasant Go API. The full build step involves compiling Rust -> C library, and linking that library to the Go code. For ergonomics of the user, we will include pre-compiled libraries to easily link with, and Go developers should just be able to import this directly.

Rust code

The Rust code lives in a sub-folder ./libwasmvm. This folder compiles to a library that can be used via FFI. It is compiled like this:

# Run unit tests
(cd libwasmvm && cargo test)

# Create release build for your current system. Uses whatever default Rust
# version you have installed.
make build-libwasmvm

# Create reproducible release builds for other systems (slow, don't use for development)
make release-build-alpine
make release-build-linux
make release-build-macos
make release-build-windows

Go code

The Go code consists of three packages:

1. The types (the github.com/CosmWasm/wasmvm/types import), using package types
2. The internal package internal/api, using package api
3. This repo (the github.com/CosmWasm/wasmvm import), using package cosmwasm

The dependencies between them are as follows:

graph TD;
    api-->types;
    cosmwasm-->types;
    cosmwasm-->api;

The Go code is built like this:

make build-go
make test

Package github.com/CosmWasm/wasmvm/types

This packages contains types used by the two other packages. It can be compiled without cgo.

# Build
go build ./types
# Build without CGO
CGO_ENABLED=0 go build ./types

Package internal/api

This package contains the code binding the libwasmvm build to the Go code. All low level FFI handling code belongs there. This package can only be built using cgo. Uing the internal/ convention makes this package fully private.

Package github.com/CosmWasm/wasmvm

This is the package users import. It can be compiled without cgo, but when you do so, a lot of functionality is removed.

# Build
go build .
# Build without CGO
CGO_ENABLED=0 go build .

In the case that it may be desirable to compile with cgo, but with libwasmvm linking disabled an additional build tag is available.

# Build with CGO, but with libwasmvm linking disabled
go build -tags "nolink_libwasmvm"

Supported Platforms

See COMPILER_VERSIONS.md for information on Go and Rust compiler support.

The Rust implementation of the VM is compiled to a library called libwasmvm. This is then linked to the Go code when the final binary is built. For that reason not all systems supported by Go are supported by this project.

Linux (tested on Ubuntu, Debian, Alpine) and macOS is supported. We are working on Windows support with very low priority (#288).

Builds of libwasmvm

Our system currently supports the following builds. In general we can only support targets that are supported by Wasmer's singlepass backend, which for example excludes all 32 bit systems.

Development

There are two halves to this code - go and rust. The first step is to ensure that there is a proper dll built for your platform. This should be api/libwasmvm.X, where X is:

• so for Linux systems
• dylib for MacOS
• dll for Windows - Not currently supported due to upstream dependency

If this is present, then make test will run the Go test suite and you can import this code freely. If it is not present you will have to build it for your system, and ideally add it to this repo with a PR (on your fork). We will set up a proper CI system for building these binaries, but we are not there yet.

To build the rust side, try make build-libwasmvm and wait for it to compile. This depends on cargo being installed with rustc version 1.47+. Generally, you can just use rustup to install all this with no problems.