Re: [Qemu-block] [Qemu-devel] [PATCH 03/15] hw/ssi: Remove SSIBus from "qemu/typedefs.h"

[Markus Armbruster]

"Michael S. Tsirkin" <address@hidden> writes:

> On Wed, Jan 16, 2019 at 12:49:07PM +0100, Paolo Bonzini wrote:
>> On 16/01/19 12:34, Gerd Hoffmann wrote:
>> >   Hi,
>> > 
>> >> typedefs.h is useful to avoid rebuilding the world too often if a type
>> >> is used many times as a pointer, but rarely as a struct and rarely has
>> >> functions called on its instances.
>> > 
>> > Related:  Can also be used to keep struct content private.  struct
>> > QemuConsole for example is private to ui/console.c, but pointers to
>> > QemuConsole are passed around alot in ui/* and hw/display/* code.
>> 
>> True, though as we switch more and more from pointers to embedded
>> structs that does not work that much anymore.  Another way to do that is
>> to split the header in include/path/to/foo.h and path/to/foo_internal.h.
>> 
>> Paolo
>
> Not sure this will help since no tool checks structure isn't
> actually used even though it's in internal.
>
> If you want to go overboard it's solvable of course, e.g.
> something like this will work:
>
>
> E.g. in virtio.h
>
> #ifndef VIRTIO_PRIVATE
> #define VIRTIO_PRIVATE(f) (VIRTIO_PIVATE_##f)
> #endif
>
> struct VirtioPrivate {
>       int VIRTIO_PRIVATE(bar);
> };
>
> and in virtio.c:
>
> #define VIRTIO_PRIVATE(f) (f)
> #include <virtio.h>

I don't like such games at all.

Instead, I'd recommend to keep internal headers out of include/, and
rely on review / grep to catch, correct and prevent inappropriate uses.