xemu/qapi
Markus Armbruster a95291007b qapi: Eliminate indirection through qmp_event_get_func_emit()
The qapi_event_send_FOO() functions emit events like this:

    QMPEventFuncEmit emit;

    emit = qmp_event_get_func_emit();
    if (!emit) {
        return;
    }

    qmp = qmp_event_build_dict("FOO");
    [put event arguments into @qmp...]

    emit(QAPI_EVENT_FOO, qmp);

The value of qmp_event_get_func_emit() depends only on the program:

* In qemu-system-FOO, it's always monitor_qapi_event_queue.

* In tests/test-qmp-event, it's always event_test_emit.

* In all other programs, it's always null.

This is exactly the kind of dependence the linker is supposed to
resolve; we don't actually need an indirection.

Note that things would fall apart if we linked more than one QAPI
schema into a single program: each set of qapi_event_send_FOO() uses
its own event enumeration, yet they share a single emit function.
Which takes the event enumeration as an argument.  Which one if
there's more than one?

More seriously: how does this work even now?  qemu-system-FOO wants
QAPIEvent, and passes a function taking that to
qmp_event_set_func_emit().  test-qmp-event wants test_QAPIEvent, and
passes a function taking that to qmp_event_set_func_emit().

It works by type trickery, of course:

    typedef void (*QMPEventFuncEmit)(unsigned event, QDict *dict);

    void qmp_event_set_func_emit(QMPEventFuncEmit emit);

    QMPEventFuncEmit qmp_event_get_func_emit(void);

We use unsigned instead of the enumeration type.  Relies on both
enumerations boiling down to unsigned, which happens to be true for
the compilers we use.

Clean this up as follows:

* Generate qapi_event_send_FOO() that call PREFIX_qapi_event_emit()
  instead of the value of qmp_event_set_func_emit().

* Generate a prototype for PREFIX_qapi_event_emit() into
  qapi-events.h.

* PREFIX_ is empty for qapi/qapi-schema.json, and test_ for
  tests/qapi-schema/qapi-schema-test.json.  It's qga_ for
  qga/qapi-schema.json, and doc-good- for
  tests/qapi-schema/doc-good.json, but those don't define any events.

* Rename monitor_qapi_event_queue() to qapi_event_emit() instead of
  passing it to qmp_event_set_func_emit().  This takes care of
  qemu-system-FOO.

* Rename event_test_emit() to test_qapi_event_emit() instead of
  passing it to qmp_event_set_func_emit().  This takes care of
  tests/test-qmp-event.

* Add a qapi_event_emit() that does nothing to stubs/monitor.c.  This
  takes care of all other programs that link code emitting QMP events.

* Drop qmp_event_set_func_emit(), qmp_event_get_func_emit().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20181218182234.28876-3-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[Commit message typos fixed]
2019-01-24 10:01:05 +01:00
..
block-core.json block: remove 'x' prefix from experimental bitmap APIs 2019-01-14 10:09:46 -06:00
block.json nbd: Remove x-nbd-server-add-bitmap 2019-01-14 10:09:46 -06:00
char.json qapi: add more conditions to SPICE 2018-12-14 06:52:48 +01:00
common.json qapi: Define PCIe link speed and width properties 2018-12-19 16:48:16 -05:00
crypto.json crypto: Fix defaults in QCryptoBlockCreateOptionsLUKS 2018-12-12 11:16:49 +00:00
introspect.json json: Update references to RFC 7159 to RFC 8259 2018-08-24 20:27:14 +02:00
job.json qapi/job: The next release will be 3.0 2018-06-29 14:20:56 +02:00
Makefile.objs qapi: rename *qmp-*-visitor* to *qobject-*-visitor* 2016-10-25 16:25:48 +02:00
migration.json qapi: add conditions to REPLICATION type/commands on the schema 2018-12-14 06:52:48 +01:00
misc.json qmp hmp: Make system_wakeup check wake-up support and run state 2018-12-18 07:55:47 +01:00
net.json qapi: break long lines at 'data' member 2018-12-13 19:20:11 +01:00
opts-visitor.c qapi: Fix QemuOpts visitor regression on unvisited input 2017-03-22 19:24:34 +01:00
qapi-clone-visitor.c qapi/qnull: Add own header 2017-11-17 18:21:30 +01:00
qapi-dealloc-visitor.c qobject: Replace qobject_incref/QINCREF qobject_decref/QDECREF 2018-05-04 08:27:53 +02:00
qapi-schema.json qapi: Define new QMP message for pvrdma 2018-12-22 11:09:56 +02:00
qapi-util.c qapi: Change data type of the FOO_lookup generated for enum FOO 2017-09-04 13:09:13 +02:00
qapi-visit-core.c Include qapi/qmp/qobject.h exactly where needed 2018-02-09 13:52:15 +01:00
qmp-dispatch.c qmp: constify qmp_is_oob() 2018-08-30 16:08:47 +02:00
qmp-event.c qapi: Eliminate indirection through qmp_event_get_func_emit() 2019-01-24 10:01:05 +01:00
qmp-registry.c qapi: Support multiple command registries per program 2017-03-05 09:12:25 +01:00
qobject-input-visitor.c qapi: Use qemu_strtod_finite() in qobject-input-visitor 2018-12-13 19:10:06 +01:00
qobject-output-visitor.c qobject: Modify qobject_ref() to return obj 2018-05-04 08:27:53 +02:00
rdma.json qapi: Define new QMP message for pvrdma 2018-12-22 11:09:56 +02:00
rocker.json qapi: The #optional tag is redundant, drop 2017-03-16 07:13:02 +01:00
run-state.json qmp: Split ShutdownCause host-qmp into quit and system-reset 2018-12-18 07:55:47 +01:00
sockets.json sockets: allow SocketAddress 'fd' to reference numeric file descriptors 2018-03-13 18:06:06 +00:00
string-input-visitor.c qapi: Rewrite string-input-visitor's integer and list parsing 2018-12-13 19:10:06 +01:00
string-output-visitor.c qapi: Use QNull for a more regular visit_type_null() 2017-07-24 13:35:11 +02:00
tpm.json qapi: break long lines at 'data' member 2018-12-13 19:20:11 +01:00
trace-events trace: forbid floating point types 2018-06-27 11:09:29 +01:00
trace.json qapi-schema: Improve section headings 2017-09-04 13:09:12 +02:00
transaction.json block: remove 'x' prefix from experimental bitmap APIs 2019-01-14 10:09:46 -06:00
ui.json qapi: break long lines at 'data' member 2018-12-13 19:20:11 +01:00