At Sun, 20 Mar 2011 08:41:50 +0100, "keyd...@gmx.de" wrote:
> I wonder how to handle
> composite objects (structs) returned by a library function that have
> themselves composite objects as fields, but these objects in turn are
> considered to be "private", as seen by them being declared like so:
>
> typedef struct xy xy;
If the shape of `struct xy' isn't exposed, then,
struct something_else {
....
xy an_xy;
....
};
isn't allowed in C. The layout of `struct' fields must be known at the
declaration.
So, either the shape of `struct xy' must be exposed before the
declaration of `struct something_else', or (more commonly) uses of `xy'
are indirect through a pointer. For example, if `something_else' is
struct something_else {
....
xy * an_xy;
....
};
then at the FFI level, you can treat the `an_xy' as a `(_cpointer 'xy)'
or just `_pointer'.
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