On 10/26/2015 01:33 AM, Markus Armbruster wrote: > Eric Blake <ebl...@redhat.com> writes: > >> On 10/23/2015 09:30 AM, Markus Armbruster wrote: >>> Eric Blake <ebl...@redhat.com> writes: >>> >>>> A previous patch (commit 1e6c1616) made it possible to >>>> directly cast from a qapi type to its base type. A future >>>> patch will do likewise for structs. However, it requires >>>> the client code to use a C cast, which turns off compiler >>>> type-safety checks if the client gets it wrong. So this >>> >>> Who's the client? Suggest to simply drop "if the client gets it wrong". >>> >>>> patch adds inline type-safe wrappers named qapi_FOO_base() >>>> for any type FOO that has a base, which can be used to >>>> upcast a qapi type to its base, then uses the new generated >>>> functions in places where we were already casting. >>>>
>> >> Indeed, if I don't port gen_upcast() to types until patch 10/25, then >> this hunk also has to move to patch 10. That means no clients of the >> upcast macros in patch 9/25, _unless_ I add testsuite coverage. Which I >> probably ought to do. >> >>>> switch (event) { >>>> case QAPI_EVENT_VNC_CONNECTED: >>>> - qapi_event_send_vnc_connected(si, vs->info->base, &error_abort); >>>> + qapi_event_send_vnc_connected(si, >>>> qapi_VncClientInfo_base(vs->info), >>>> + &error_abort); >>>> break; >>>> case QAPI_EVENT_VNC_INITIALIZED: >>>> qapi_event_send_vnc_initialized(si, vs->info, &error_abort); >>> >>> Not a single cast to union base? >> >> Not that I could find. So I'll have to create one in the testsuite. > > I guess I'd introduce gen_upcast() only with its first real user, > i.e. when unboxing struct base. At that time, its obvious > implementation should work for both struct and union, even though we > actually use it only for struct. If you want to add a test case for > unions, go ahead. I'm not sure I'd bother, because once we unify code > generation for the two, testing them separately won't add much value > anymore. It sounds like I have two options for v11: 1. Keep 9/25 introducing gen_upcast(), just for union types, and including testsuite coverage. In 10/25, make use of the upcast functions to struct as part of making structs sane. 2. Swap the patch order: do 10/25 to alter struct layout first, using ugly casts; then implement 9/25 that adds gen_upcast() and fixes the ugly casts to instead use the new upcast functions. I can go either way, so do you have any preference? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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