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Rather than storing a base class as a pointer to a box, just
store the fields of that base class in the same order, so that
a child struct can be directly cast to its parent. This gives
less malloc overhead, less pointer dereferencing, and even less
generated code. Compare to the earlier commit 1e6c1616a "qapi:
Generate a nicer struct for flat unions" (although that patch
had fewer places to change, as less of qemu was directly using
qapi structs for flat unions). It also allows us to turn on
automatic type-safe wrappers for upcasting to the base class
of a struct.
Changes to the generated code look like this in qapi-types.h:
| struct SpiceChannel {
|- SpiceBasicInfo *base;
|+ /* Members inherited from SpiceBasicInfo: */
|+ char *host;
|+ char *port;
|+ NetworkAddressFamily family;
|+ /* Own members: */
| int64_t connection_id;
as well as additional upcast functions like qapi_SpiceChannel_base().
Meanwhile, changes to qapi-visit.c look like:
| static void visit_type_SpiceChannel_fields(Visitor *v, SpiceChannel **obj, Error **errp)
| {
| Error *err = NULL;
|
|- visit_type_implicit_SpiceBasicInfo(v, &(*obj)->base, &err);
|+ visit_type_SpiceBasicInfo_fields(v, (SpiceBasicInfo **)obj, &err);
| if (err) {
(the cast is necessary, since our upcast wrappers only deal with a
single pointer, not pointer-to-pointer); plus the wholesale
elimination of some now-unused visit_type_implicit_FOO() functions.
Without boxing, the corner case of one empty struct having
another empty struct as its base type now requires inserting a
dummy member (previously, the 'Base *base' member sufficed).
And now that we no longer consume a 'base' member in the generated
C struct, we can delete the former negative struct-base-clash-base
test.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1445898903-12082-11-git-send-email-eblake@redhat.com>
[Commit message tweaked slightly]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
|
|
|
Expose some weaknesses in the generator: we don't always forbid
the generation of structs that contain multiple members that map
to the same C or QMP name. This has already been marked FIXME in
qapi.py in commit d90675f, but having more tests will make sure
future patches produce desired behavior; and updating existing
patches to better document things doesn't hurt, either. Some of
these collisions are already caught in the old-style parser
checks, but ultimately we want all collisions to be caught in the
new-style QAPISchema*.check() methods.
This patch focuses on C struct members, and does not consider
collisions between commands and events (affecting C function
names), or even collisions between generated C type names with
user type names (for things like automatic FOOList struct
representing array types or FOOKind for an implicit enum).
There are two types of struct collisions we want to catch:
1) Collision between two keys in a JSON object. qapi.py prevents
that within a single struct (see test duplicate-key), but it is
possible to have collisions between a type's members and its
base type's members (existing tests struct-base-clash,
struct-base-clash-deep), and its flat union variant members
(renamed test flat-union-clash-member).
2) Collision between two members of the C struct that is generated
for a given QAPI type:
a) Multiple QAPI names map to the same C name (new test
args-name-clash)
b) A QAPI name maps to a C name that is used for another purpose
(new tests flat-union-clash-branch, struct-base-clash-base,
union-clash-data). We already fixed some such cases in commit
0f61af3e and 1e6c1616, but more remain.
c) Two C names generated for other purposes clash
(updated test alternate-clash, new test union-clash-branches,
union-clash-type, flat-union-clash-type)
Ultimately, if we need to have a flat union where a tag value
clashes with a base member name, we could change the generator to
name the union (using 'foo.u.value' rather than 'foo.value') or
otherwise munge the C name corresponding to tag values. But
unless such a need arises, it will probably be easier to just
forbid these collisions.
Some of these negative tests will be deleted later, and positive
tests added to qapi-schema-test.json in their place, when the
generator code is reworked to avoid particular code generation
collisions in class 2).
[Note that viewing this patch with git rename detection enabled
may see some confusion due to renaming some tests while adding
others, but where the content is similar enough that git picks
the wrong pre- and post-patch files to associate]
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1443565276-4535-6-git-send-email-eblake@redhat.com>
[Improve commit message and comments a bit, drop an unrelated test]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
|