null references to functions

[sjamesr]

I created WebAssembly/wasm-c-api#193, but I thought I'd cross-post the issue to see if anybody here has a solution.

I don't see a way to use wasm_c_api.h to create null function references. We have wasm_func_as_ref to turn non-null wasm_func_t into wasm_ref_t, but I'd like to be able to obtain a wasm_ref_t representing a null function.

Is this feature missing in the API, or am I just not seeing it?

BTW, the purpose is to be able to implement certain spec tests, such as

(assert_return (invoke "select-funcref" (ref.null func) (ref.null func) (i32.const 1)) (ref.null func))

(see the original test)