[xanathar]

1) Do not free memory allocated in one language (even more: in one library unless explicitly documented so) into another. Rust can use a custom allocator, and what it uses by default is an implementation detail that can change at a blink.

2) Do not use Vec<T> to pass arrays to C. Use boxed slices. Do not even try to allocate a Vec and free a Box... how can it even work?!

3) free(ptr) can be called even in ptr is NULL

4) ... I frankly stopped reading. I will never know if Rust actually needs Go's defer or not.