wasmu 🕸️🤏

A small, embeddable WebAssembly runtime for memory-constrained environments.

wasmu was primarily designed as a runtime for WebAssembly apps on the DigiCron retro smartwatch. wasmu focuses more on memory usage over performance, making it suitable for any environment where memory usage is a concern.

The name wasmu is a play on words — wasm is an initialism for WebAssembly, and mu — or µ — is the SI unit prefix for micro.

wasmu is currently capable of running simple WebAssembly binaries, but is likely to experience issues with more complex binaries (such as those produced by a compiler) at this stage.

Features

• In-place interpretation, meaning that wasmu doesn't try to recompile the WebAssembly code into native machine code or another intermediate representation
  • Low memory footprint — wasmu only needs to allocate a few tables and stacks alongside your WebAsesmbly code buffer
  • Architecture-independent — works on a wide range of CPU architectures
• Embeddable — single-header file that doesn't need stdio or stdlib to get working
  • Written in C, can also be embedded in C++ projects
  • Steppable interpreter, preventing infinite loops in WebAssembly from blocking the main thread
• Customisable to fit your specific needs
  • Define native modules that can be called from WebAssembly code
• Designed for microcontrollers, but works on conventional computers and other platforms

Building

Before building wasmu, you will need to install some dependencies:

sudo apt install gcc wabt

To build the library, run:

./build.sh

The built library will then be available at dist/wasmu.h, with the configuration header file at dist/wasmu-config.h.

Testing

To run the unit tests, run:

./build.sh --test

Logs for each test are available at test/$TEST/build/test.log, where $TEST is the name of a test.