There are stray references to the concept of multiple address spaces (or 'memories') in the wasm spec at present, and I recall at one point you may have always

There are stray references to the concept of multiple address spaces (or 'memories') in the wasm spec at present, and I recall at one point you may have always been passing 'memory #0' to your load/store opcodes before it was dropped from 1.0. It looks like people are still working on that as the solution. https://github.com/WebAssembly/multi-memory https://github.com/WebAssembly/multi-memory > Add a memory index to all memory-related instructions. > Loads and stores have the memop field, in which we can allocate a bit indicating a memory index immediate in the binary format. > All other memory instruction already have a memory index immediate (which currently has to be 0).