`wasm_trap_new` expects a `wasm_message_t`. It's a type alias to
`wasm_name_t` with the exception that it represents a null-terminated
string.
When calling `wasm_trap_new`, no check was present to ensure the
string was well-formed. That's a first issue. But in the best
scenario, the string was correctly formed and was
null-terminated. This string was transformed to a Rust `String` —with
the null byte!— and passed to `RuntimeError`.
Then in `wasm_trap_message`, another null byte was pushed at the end
of the message. It's been introduced in
https://github.com/wasmerio/wasmer/pull/1947. It results in a
doubly-null-terminated string, which is incorrect.
This patch does the following:
1. It checks that the string given to `wasm_trap_new` contains a
null-terminated string or not, and will act accordingly. Note that
it's possible to pass a non-null-terminated string, and it will
still work because this detail is vicious. The idea is to get a
well-formed `RuntimeError` in anycase.
* If no null byte is found, the string is passed to `RuntimeError`
as a valid Rust string,
* If a null byte is found at the end of the string, a new string is
passed to `RuntimeError` but without the final null byte,
* If a null byte is found but not at the end, it's considered as an
error,
* If the string contains invalid UTF-8 bytes, it's considered as an
error.
2. It updates `wasm_trap_message` to always add a null byte at the end
of the returned owned string.
3. It adds test cases when passing a null-terminated or a
non-null-terminated string to `wasm_trap_new` and to compare the
results to `wasm_trap_message`.
