Hey @echojoys ,
I want to follow up on the topic of “safe” string returns through multi-value returns from WASM. I implemented this feature here and expect support for multi-value returns to land very soon in wasmex.
After the MR landed, you can have Rust code that returns a string pointer and length from the same function call:
#[no_mangle]
pub fn to_string(a: i32) -> (i32, i32) {
let str = a.to_string();
(str.as_ptr() as i32, str.len() as i32)
}
from Elixir you can call that function like any old function:
{:ok, [pointer, length]} = Wasmex.call_function(instance, :to_string, [54321])
{:ok, memory} = Wasmex.memory(instance)
assert Wasmex.Memory.read_string(store, memory, pointer, length) == "54321"
(the code snippets are an extract from Wasmex tests, have a look at those wasmex_test.exs tests to see more examples)
I hope this helps! 
cheers,
tessi
