qapi: Don't box struct branch of alternate
There's no reason to do two malloc's for an alternate type visiting
a QAPI struct; let's just inline the struct directly as the C union
branch of the struct.
Surprisingly, no clients were actually using the struct member prior
to this patch outside of the testsuite; an earlier patch in the series
added some testsuite coverage to make the effect of this patch more
obvious.
In qapi.py, c_type() gains a new is_unboxed flag to control when we
are emitting a C struct unboxed within the context of an outer
struct (different from our other two modes of usage with no flags
for normal local variable declarations, and with is_param for adding
'const' in a parameter list). I don't know if there is any more
pythonic way of collapsing the two flags into a single parameter,
as we never have a caller setting both flags at once.
Ultimately, we want to also unbox branches for QAPI unions, but as
that touches a lot more client code, it is better as separate
patches. But since unions and alternates share gen_variants(), I
had to hack in a way to test if we are visiting an alternate type
for setting the is_unboxed flag: look for a non-object branch.
This works because alternates have at least two branches, with at
most one object branch, while unions have only object branches.
The hack will go away in a later patch.
The generated code difference to qapi-types.h is relatively small:
| struct BlockdevRef {
| QType type;
| union { /* union tag is @type */
| void *data;
|- BlockdevOptions *definition;
|+ BlockdevOptions definition;
| char *reference;
| } u;
| };
The corresponding spot in qapi-visit.c calls visit_type_FOO(), which
first calls visit_start_struct() to allocate or deallocate the member
and handle a layer of {} from the JSON stream, then visits the
members. To peel off the indirection and the memory management that
comes with it, we inline this call, then suppress allocation /
deallocation by passing NULL to visit_start_struct(), and adjust the
member visit:
| switch ((*obj)->type) {
| case QTYPE_QDICT:
|- visit_type_BlockdevOptions(v, name, &(*obj)->u.definition, &err);
|+ visit_start_struct(v, name, NULL, 0, &err);
|+ if (err) {
|+ break;
|+ }
|+ visit_type_BlockdevOptions_fields(v, &(*obj)->u.definition, &err);
|+ error_propagate(errp, err);
|+ err = NULL;
|+ visit_end_struct(v, &err);
| break;
| case QTYPE_QSTRING:
| visit_type_str(v, name, &(*obj)->u.reference, &err);
The visit of non-object fields is unchanged.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1455778109-6278-13-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index d7d7ed5..f4e38d1 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -201,11 +201,14 @@
def gen_visit_alternate(name, variants):
promote_int = 'true'
+ ret = ''
for var in variants.variants:
if var.type.alternate_qtype() == 'QTYPE_QINT':
promote_int = 'false'
+ if isinstance(var.type, QAPISchemaObjectType):
+ ret += gen_visit_fields_decl(var.type)
- ret = mcgen('''
+ ret += mcgen('''
void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp)
{
@@ -221,17 +224,35 @@
}
switch ((*obj)->type) {
''',
- c_name=c_name(name), promote_int=promote_int)
+ c_name=c_name(name), promote_int=promote_int)
for var in variants.variants:
ret += mcgen('''
case %(case)s:
- visit_type_%(c_type)s(v, name, &(*obj)->u.%(c_name)s, &err);
- break;
''',
- case=var.type.alternate_qtype(),
- c_type=var.type.c_name(),
- c_name=c_name(var.name))
+ case=var.type.alternate_qtype())
+ if isinstance(var.type, QAPISchemaObjectType):
+ ret += mcgen('''
+ visit_start_struct(v, name, NULL, 0, &err);
+ if (err) {
+ break;
+ }
+ visit_type_%(c_type)s_fields(v, &(*obj)->u.%(c_name)s, &err);
+ error_propagate(errp, err);
+ err = NULL;
+ visit_end_struct(v, &err);
+''',
+ c_type=var.type.c_name(),
+ c_name=c_name(var.name))
+ else:
+ ret += mcgen('''
+ visit_type_%(c_type)s(v, name, &(*obj)->u.%(c_name)s, &err);
+''',
+ c_type=var.type.c_name(),
+ c_name=c_name(var.name))
+ ret += mcgen('''
+ break;
+''')
ret += mcgen('''
default: