[Qemu-devel] [PATCH v5 06/14] qapi-event: Slightly shrink generated code

[Eric Blake]

Slightly rearrange the code in gen_event_send() for less generated
output, by initializing 'emit' sooner, deferring an assertion
to qdict_put_obj, and dropping a now-unused 'obj' local variable.

While at it, document a FIXME related to the potential for a
compiler naming collision - if the user ever creates a QAPI event
whose name matches 'errp' or one of our local variables (like
'emit'), we'll have to revisit how we generate functions to
avoid the problem.

|@@ -25,16 +25,13 @@ void qapi_event_send_acpi_device_ost(ACP
| {
|     QDict *qmp;
|     Error *err = NULL;
|-    QMPEventFuncEmit emit;
|+    QMPEventFuncEmit emit = qmp_event_get_func_emit();
|     QmpOutputVisitor *qov;
|     Visitor *v;
|-    QObject *obj;
|
|-    emit = qmp_event_get_func_emit();
|     if (!emit) {
|         return;
|     }
|-
|     qmp = qmp_event_build_dict("ACPI_DEVICE_OST");
|
|     qov = qmp_output_visitor_new();
|@@ -53,11 +50,7 @@ out_obj:
|     if (err) {
|         goto out;
|     }
|-
|-    obj = qmp_output_get_qobject(qov);
|-    g_assert(obj);
|-
|-    qdict_put_obj(qmp, "data", obj);
|+    qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
|     emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err);
|
| out:

Signed-off-by: Eric Blake <address@hidden>

---
v5: new patch
---
 scripts/qapi-event.py | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/scripts/qapi-event.py b/scripts/qapi-event.py
index c03cb78..02c9556 100644
--- a/scripts/qapi-event.py
+++ b/scripts/qapi-event.py
@@ -29,13 +29,19 @@ def gen_event_send_decl(name, arg_type):


 def gen_event_send(name, arg_type):
+    # FIXME: Our declaration of local variables (and of 'errp' in the
+    # parameter list) can collide with exploded members of the event's
+    # data type passed in as parameters.  If this collision ever hits in
+    # practice, we can rename our local variables with a leading _ prefix,
+    # or split the code into a wrapper function that creates a boxed
+    # 'param' object then calls another to do the real work.
     ret = mcgen('''

 %(proto)s
 {
     QDict *qmp;
     Error *err = NULL;
-    QMPEventFuncEmit emit;
+    QMPEventFuncEmit emit = qmp_event_get_func_emit();
 ''',
                 proto=gen_event_send_proto(name, arg_type))

@@ -43,16 +49,13 @@ def gen_event_send(name, arg_type):
         ret += mcgen('''
     QmpOutputVisitor *qov;
     Visitor *v;
-    QObject *obj;
-
 ''')

     ret += mcgen('''
-    emit = qmp_event_get_func_emit();
+
     if (!emit) {
         return;
     }
-
     qmp = qmp_event_build_dict("%(name)s");

 ''',
@@ -76,11 +79,7 @@ out_obj:
     if (err) {
         goto out;
     }
-
-    obj = qmp_output_get_qobject(qov);
-    g_assert(obj);
-
-    qdict_put_obj(qmp, "data", obj);
+    qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
 ''')

     ret += mcgen('''
-- 
2.5.0