Re: libhurd-cap-server: making API compatibility easier

[Ludovic Courtès]

"Neal H. Walfield" <address@hidden> writes:

> I am not entirely clear what you intend.  Do you want to apply this
> technique to hurd_cap_obj_t and hurd_cap_class_t?

I was trying to address the question of how to allow caller object
allocation while not exposing data structures.  In your previous
example, you mentioned that this would be needed for `struct
hurd_cap_ctx_cap_use' and you suggested that this could be achieved by
defining a function that returns the size of this data structure:

  struct hurd_cap_ctx_cap_use *cap_ctx = alloca (hurd_cap_ctx_size ());

I'm just saying that instead of making an actual function call (not
inlined) to `hurd_cap_ctx_size ()', the caller could do something like:

  struct hurd_cap_ctx_cap_use *cap_ctx =
    alloca (hurd_class_instance_size (&hurd_cap_ctx_cap_use_class));

And this even saves a function call since `hurd_class_instance_size ()'
can be inlined.

Hope this makes sense,
Ludovic.