Using wasm_externref_ref2obj/obj2ref safely with untrusted wasm

[behdad]

I'm writing native code interacting with untrusted wasm. I'm using wasm_externref_ref2obj/obj2ref to convert from my native objects to/from refs to pass to the wasm. I have multiple different object types that I convert using this API. However I find that the wasm can easily crash my code by passing a reference number to the wrong API.

For example, if I have to type font_t and buffer_t, then passing a reference belonging to a font_t to an API taking a buffer_t will successfully pass ref2obj and my native code will try to treat the returned void* object as a buffer object, whereas it's actually a font object.

Am I missing something? Or is this not possible and my native code has to have a way to know what object type it's dealing with (like eg. Javascript or Python etc would know)?