Thoughts on WebAssembly as a stack machine

This week the article Wasm is not quite a stack machine has been making the rounds and has caught my eye. The post claims that WASM is not a pure stack machine because it has locals and is missing some stack manipulation operations like dup and swap. While I don't necessarily disagree, IMHO it's a bit of a semantic discussion because - to the best of my knowledge - there is no formal definition of what is a stack machine. Wikipedia, for example, says: [...], a stack machine is a computer processor or a process virtual machine in which the primary interaction is moving short-lived temporary values to and from a push-down stack. WASM certainly fits this definition; the primary interaction is through the stack, though WASM is augmented with an infinite register file (locals). The more purist stack machines like Forth are only limited to the stack and a memory (pointers into which are managed on the stack); WASM has these too, plus the registers. Speaking of Forth, the mention of dup…