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authorEric Blake <eblake@redhat.com>2016-02-17 23:48:26 -0700
committerMarkus Armbruster <armbru@redhat.com>2016-02-19 11:08:57 +0100
commitbecceedc4d9bc1435099c90a0514945a89844d3a (patch)
tree514ffcbc4c7fecc0a372808baa380ec35b97b9a0 /scripts/qapi.py
parent2208d64998c5f867ccee7eeee298971685bf822d (diff)
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>
Diffstat (limited to 'scripts/qapi.py')
-rw-r--r--scripts/qapi.py12
1 files changed, 7 insertions, 5 deletions
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 17bf633e39..8497777d94 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -824,7 +824,7 @@ class QAPISchemaVisitor(object):
class QAPISchemaType(QAPISchemaEntity):
- def c_type(self, is_param=False):
+ def c_type(self, is_param=False, is_unboxed=False):
return c_name(self.name) + pointer_suffix
def c_null(self):
@@ -857,7 +857,7 @@ class QAPISchemaBuiltinType(QAPISchemaType):
def c_name(self):
return self.name
- def c_type(self, is_param=False):
+ def c_type(self, is_param=False, is_unboxed=False):
if is_param and self.name == 'str':
return 'const ' + self._c_type_name
return self._c_type_name
@@ -891,7 +891,7 @@ class QAPISchemaEnumType(QAPISchemaType):
# See QAPISchema._make_implicit_enum_type()
return self.name.endswith('Kind')
- def c_type(self, is_param=False):
+ def c_type(self, is_param=False, is_unboxed=False):
return c_name(self.name)
def member_names(self):
@@ -987,9 +987,11 @@ class QAPISchemaObjectType(QAPISchemaType):
assert not self.is_implicit()
return QAPISchemaType.c_name(self)
- def c_type(self, is_param=False):
+ def c_type(self, is_param=False, is_unboxed=False):
assert not self.is_implicit()
- return QAPISchemaType.c_type(self)
+ if is_unboxed:
+ return c_name(self.name)
+ return c_name(self.name) + pointer_suffix
def json_type(self):
return 'object'