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References

&Struct

(Supported by c, cpp, and nanobind, queried with #[diplomat::cfg(supports=struct_refs)])

Structs can be borrowed immutably as parameters to functions, but nowhere else.

&mut Struct

(Supported by c, cpp, and nanobind, queried with #[diplomat::cfg(supports=mut_struct_refs)])

Structs can be borrowed mutably as parameters to functions, but nowhere else. Mutable structs must be marked with #[diplomat::attr(*, mut_struct_ref)], as not every backend will represent its structure identically to how it is stored in the C ABI. Therefore, most backends will:

  1. Clone the structure into a C-ABI friendly struct
  2. Call the mutable method on the C-ABI friendly struct
  3. Clone the C-ABI friendly struct back into the native backend type

To assist in making mutable structs possible, some backends will codegen different structure field types from normal behavior. See the C++ backend’s docs for an example of why this might be.