1850592 - Autogenerate C++ bindings for authrs_bridge

Status: NEW

(Core :: DOM: Web Authentication, enhancement, P3)

Description

[John Schanck [:jschanck]]

We should use cbindgen to create bindings for authrs_transport_constructor and authrs_webauthn_att_obj_constructor. There's a very minor obstacle to doing this at the moment. That is

1. the rust side defines its out parameters as *mut *const T,
2. cbindgen produces a header with out params of type const T**, and
3. the C++ side uses getterAddRefs which converts to T **.

This results in a compile error:
candidate function not viable: no known conversion from 'nsGetterAddRefs<T>' to 'const T **' .

Comment 1

[John Schanck [:jschanck]]

Attachment: WIP: Bug 1850592 - autogenerate C bindings for authrs_bridge.

Comment 2

[Emilio Cobos Álvarez [:emilio]]

If that's the only blocker, we could define the rust function to use *mut *mut T, right? It should automatically coerce to *mut *const T if needed.

Comment 3

[John Schanck [:jschanck]]

The compiler won't automatically coerce the inner pointer type, but using *mut *mut T and manually coercing is certainly one solution.

FWIW, there are a number of other instances of this pattern, and most of those could benefit from automatic binding generation.

Comment 4

[Emilio Cobos Álvarez [:emilio]]

An even better alternative would be to make getterAddrefs coerce to const T**, I guess.