This directory contains a build configuration for WASI support, plus a basic sample. This is not intended for production use, nor is it currently supported. This is a step towards possible future support.

The mechanism for executing .NET code in a WASI runtime environment is equivalent to how dotnet.wasm executes .NET code in a browser environment. That is, it runs the Mono interpreter to execute .NET bytecode that has been built in the normal way. It should also work with AOT but this is not yet attempted.

To build the wasi runtime we need the file wasm_m2n_invoke.g.h which is generated when compiling wasm runtime

make -C src/mono/wasm provision-wasm
export EMSDK_PATH=[path_printed_by_provision_wasm]
./build.sh mono+libs -os browser

Currently this can only be built in Linux or WSL (tested on Windows 11). Simply run make in this directory. It will automatically download and use WASI SDK.

The resulting libraries are placed in (repo_root)/artifacts/bin/mono/Wasi.Release.

To run an application in a WASI environment, you need to have a WASI runtime available. For example, download wasmtime and make sure it's available on PATH:

export PATH=~/wasmtime-v0.31.0-x86_64-linux
wasmtime --version

Other WASI runtimes also work. Tested: wamr, wasmer.

You also need to have a working installation of .NET 7 including the browser-wasm runtime pack. For example, obtain the .NET SDK daily build (main branch), and ensure the browser-wasm pack is installed:

dotnet workload install wasm-tools -s https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet7/nuget/v3/index.json

To make this available to the build scripts, supply environment variables. Example:

export DOTNET_ROOT=~/dotnet7
export BROWSER_WASM_RUNTIME_PATH=$(DOTNET_ROOT)/packs/Microsoft.NETCore.App.Runtime.Mono.browser-wasm/7.0.0-alpha.1.22061.11/runtimes/browser-wasm

You'll need to update these paths to match the location where you extracted the .NET daily SDK build and the exact version of the browser-wasm pack you received.

Finally, you can build and run the sample:

cd sample/console
make run

Also, you can build and debug the sample:

cd sample/console
make debug

Using Visual Studio code, add a breakpoint on Program.cs line 17. Download the Mono Debug extension and configure a launch.json like this:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Attach",
            "type": "mono",
            "request": "attach",
            "address": "localhost",
            "port": 64000
        }
    ]
}