A stackless, in-place interpreter for WebAssembly written in Zig.

Inspired by the following projects:

• piccolo, a stackless Lua interpreter
• "A fast in-place interpreter for WebAssembly" (2022), which provides the design and data structures that make fast in-place interpretation possible.

Note that wasmstint is still in development and it's API is very unstable!

• Fuel-metering (like all the other WASM runtimes)
• Full control over memory allocations thanks to Zig's std.mem.Allocator API.
• Passes specification testsuite tests (for supported WASM proposals)

wasmstint currently supports and passes test for WebAssembly 2.0 as well as few additional proposals:

• Mutable Globals
• Non-Trapping Float-to-Int Conversions
• Sign Extension Operators
• Multi-Value
• Reference Types
• Bulk Memory Operations
• Fixed-Width SIMD
• Tail Call
• Extended Constant Expressions

Currently, support for all of these features is always enabled. Disabling of features at compile- time may be added in the future.

wasmstint currently has incomplete support for wasi_snapshot_preview1 applications.

To run the WASI preview 1 interpreter, run the following command:

zig build run-wasip1 -- -m /path/to/application.wasm --dir /path/to/dir guest/name rw

Due to the way WASI sandboxing is implemented on Windows, building the WASI interpreter requires targeting at least Windows 10 version 1607 or higher.

zig build run-wasip1 -Dtarget=x86_64-windows.win10_rs1

Run zig build --help for more information.

wasmstint is currently only known to build and run its tests successfully for the x86_64-linux and x86_64-windows targets. Building for 32-bit targets is likely to result in compile errors. Due to the use of tail calls in wasmstint, building for non-x86_64 targets also currently requires the LLVM backend, set with the -Duse-llvm=always build option.

Additionally, big-endian targets are not supported at all.