xemu/include
Eric Blake 3bc97fd592 qapi: Add visit_type_null() visitor
Right now, qmp-output-visitor happens to produce a QNull result
if nothing is actually visited between the creation of the visitor
and the request for the resulting QObject.  A stronger protocol
would require that a QMP output visit MUST visit something.  But
to still be able to produce a JSON 'null' output, we need a new
visitor function that states our intentions.  Yes, we could say
that such a visit must go through visit_type_any(), but that
feels clunky.

So this patch introduces the new visit_type_null() interface and
its no-op interface in the dealloc visitor, and stubs in the
qmp visitors (the next patch will finish the implementation).
For the visitors that will not implement the callback, document
the situation. The code in qapi-visit-core unconditionally
dereferences the callback pointer, so that a segfault will inform
a developer if they need to implement the callback for their
choice of visitor.

Note that JSON has a primitive null type, with the single value
null; likewise with the QNull type for QObject; but for QAPI,
we just have the 'null' value without a null type.  We may
eventually want to add more support in QAPI for null (most likely,
we'd use it via an alternate type that permits 'null' or an
object); but we'll create that usage when we need it.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-15-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-05-12 09:47:54 +02:00
..
block block: Fix bdrv_drain in coroutine 2016-04-11 16:59:09 +01:00
crypto include/crypto: Include qapi-types.h or qemu/bswap.h instead of qemu-common.h 2016-03-22 22:20:16 +01:00
disas
exec qemu-log: dfilter-ise exec, out_asm, op and opt_op 2016-03-22 22:20:18 +01:00
fpu include: Clean up includes 2016-02-23 12:43:05 +00:00
hw virtio-input: support absolute axis config in pass-through 2016-04-13 17:26:12 +02:00
io io: implement socket watch for win32 using WSAEventSelect+select 2016-03-10 17:19:07 +00:00
libdecnumber include: Clean up includes 2016-02-23 12:43:05 +00:00
migration migration (ordinary): move bdrv_invalidate_cache_all of of coroutine context 2016-02-26 20:39:50 +05:30
monitor Use scripts/clean-includes to drop redundant qemu/typedefs.h 2016-03-22 22:20:16 +01:00
net Use scripts/clean-includes to drop redundant qemu/typedefs.h 2016-03-22 22:20:16 +01:00
qapi qapi: Add visit_type_null() visitor 2016-05-12 09:47:54 +02:00
qemu event-notifier: Add "is_external" parameter 2016-04-22 16:43:56 +02:00
qom qom: -object error messages lost location, restore it 2016-04-28 08:19:36 +02:00
standard-headers update Linux headers to 4.6 2016-04-05 11:46:52 +02:00
sysemu kvm: add kvm_device_supported() helper function 2016-03-30 17:27:24 +01:00
ui ui/virtio-gpu: add and use qemu_create_displaysurface_pixman 2016-04-11 12:32:01 +02:00
elf.h include: Clean up includes 2016-02-23 12:43:05 +00:00
glib-compat.h
qemu-common.h util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
qemu-io.h
qjson.h
trace-tcg.h
trace.h