On Fri, Mar 19, 2010 at 01:41:59AM +0000, Jamie Lokier wrote: > Juan Quintela wrote: > > vstrucut virtio_common *create_virtio_comon(...., size we really want); > > Again, this implements superclass/subclass as well as you can implemnt > > it in C. > > It would be more type-safe for create_virtio_common() to be a macro > taking the subclass *type* rather than sizeof. > > And it would make the calls short: No need to cast the result, because > the macro would return the desired type (doing the cast itself). > > #define create_virtio_common(...., type) \ > ((type *)_create_virtio_common(...., sizeof(type))) > > Once you have that, it's easy to change to add a field name and > container_of: > > #define create_virtio_common(...., type, field) \ > (container_of(_create_virtio_common(...., sizeof(type)), type, field)) > > That gives you malloc in common init, and type-safe callers everywhere > (no possibility for mistaken sizeof). > > I think it's a simpler to use API and better at protecting against > caller mistakes; you may disagree. > > -- Jamie
That's version 1 of my patch. Version 2 removed even need for macro completely by moving allocations to the caller. -- MST
