Implementing correct proc_exit in C host is impossible

[squrky]

Hi,

It doesn't seem to be possible to implement a proc_exit host function in C that produces an exit code trap. Specifically, I believe we're missing a function that can produce a trap instance that (when transformed into an error) will satisfy the requirements of wasmtime_error_exit_status.

Please let me know if you need further clarification from me.

Best.

[alexcrichton]

Yeah I think this will involve a new API to create a wasmtime_error_t from a trap code which creates a WASI exit trap. Should be reasonable to add!

[squrky]

Great! I'd offer to have a go at this myself but I think I'd have to learn Rust first!