Devcontainer WASM-Zig

Simple devcontainer for Zig development for WebAssembly and WASI

Usage

Github Codespaces

Just click the button:

Visual Studio Code

Note this assumes that you have the VS code support for remote containers and docker installed on your machine.

git clone https://github.com/dev-wasm/dev-wasm-zig
cd dev-wasm-zig
code ./

Visual studio should prompt you to see if you want to relaunch the workspace in a container, you do.

Building and Running

Basic example

zig build-exe src/main.zig -target wasm32-wasi
wasmtime main.wasm --dir .

Web serving with WAGI

Coming soon

Http client example

NB: this example uses an experimental wasmtime-http that incorporates a highly experimental HTTP client library that is not yet part of the WASI specification. Use at your own risk, things are likely to change drastically in the future.

# Build it
$ zig build-exe src/http.zig -target wasm32-wasi
# Without any approved URLs it fails
$ wasmtime-http --wasi-modules=experimental-wasi-http http.wasm
Response Error: 7
# With approved URLs it works
$  WASI_HTTP_ALLOWED_HOSTS=https://postman-echo.com wasmtime-http --wasi-modules=experimental-wasi-http http.wasmRequest succeeded: 200
Content length: 236
{"args":{},"headers":{"x-forwarded-proto":"https","x-forwarded-port":"443","host":"postman-echo.com","x-amzn-trace-id":"Root=1-63af6c37-35d6bd1e4fe55f022cd62b81","content-length":"0","accept":"*/*"},"url":"https://postman-echo.com/get"}

Debugging

Both lldb and gdb work. There is vscode debugger integration in .vscode/launch.json so you should be able to use F5 to launch the debugger.

If you want to debug from the command line:

$ lldb wasmtime
# Disable dslr so debugging works in a container
$ settings set target.disable-aslr false
# Set a break point
$ b src/main.zig:8
# Start running
$ run -g main.wasm
...