You need to think of wasm as a completely separate environment so you cannot
really share anything but `ptr UncheckedArray[uint8]` or `cstring` **from** the
VM to the host since the VM and the Nim code have two completely different
runtimes and data layout. The VM is also sandboxed so it cannot just get
arbitrary pointers from the host and use them. It is best to make host
procedures that take in the pointers and arguments and do the operations in
native code. From my understanding of wasm if you want to write to a buffer and
return it to the host you first need to call the VM's alloc procedure, then
pass that returned `WasmPtr` to your wasm procedure. It then will write to it
in the VM memory (Though this can all be done inside the VM of course and it
just returns a `i32` which would be a `WasmPtr`). From there you need to
convert that `WasmPtr` to a native pointer then you can extract the data how
you need, be that allocating a `seq[uint8]` and copying the data to that or
`cast[ptr UncheckedArray[uint8]]`. I do think I started on a general interface
for converting from the VM representation to the host for the return value but
I do not recall what happened to that.
