Notes

Difference from Wasm spec

  • No SIMD

  • Multiple memory support

  • Multiple function results & block parameters/results

  • 64-bit memory address space (memory64) is supported alongside the 32-bit default; per-memory selection is carried by Limits::is64.

What’s new in 1.3

  • New custom recursive-descent WAT parser replacing the previous ANTLR4-based one — faster builds and a smaller binary.

  • Parser, validator and encoder support for the exception-handling proposal (try_table, throw, throw_ref) and for the GC / typed-references opcodes (struct, array, ref.test / ref.cast, i31).

  • New POSIX-style host modules sys_fs and sys_proc — see Host modules.

  • wasmvm --args ... forwards command-line arguments to the running module via sys_proc.argv*.

  • Windows / MSVC build support; CI runs on Linux, macOS and Windows.