On 03/03/2016 04:56 AM, Markus Armbruster wrote: > Eric Blake <ebl...@redhat.com> writes: > >> When first introduced, neither branch of gen_visit_members_call() >> would output a goto. But now that the implicit struct visit >> always ends with a goto, we should do the same for regular >> struct visits, so that callers don't have to worry about whether >> they are creating two identical goto's in a row. >> >> Generated code gets slightly larger; if desired, we could patch >> qapi.py:gen_visit_members() to have a mode where it skips the >> final goto and leave it up to the callers when to use that mode, >> but that adds more maintenance burden when the compiler should >> be smart enough to not bloat the .o file just because the .c >> file got larger. >> >> Signed-off-by: Eric Blake <ebl...@redhat.com> >>
>> +++ b/scripts/qapi-visit.py >> @@ -48,6 +48,7 @@ def gen_visit_members_call(typ, direct_name, >> implicit_name=None): > assert isinstance(typ, QAPISchemaObjectType) > if typ.is_empty(): > pass > elif typ.is_implicit(): > assert implicit_name > assert not typ.variants > ret += gen_visit_members(typ.members, prefix=implicit_name) > > This is the goto-generating part mentioned in the commit message. > >> @@ -95,9 +95,9 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s >> *obj, Error **errp) >> } >> ''') >> >> - # 'goto out' produced for base, by gen_visit_members() for each member, >> - # and if variants were present >> - if base or members or variants: >> + # 'goto out' produced for non-empty base, by gen_visit_members() for >> + # each member, and if variants were present >> + if (base and not base.is_empty()) or members or variants: >> ret += mcgen(''' >> >> out: > > Uh, sure this hunk belongs to this patch? Unfortunately, yeah - because the empty base case doesn't generate a goto. I'm leaning more and more towards not bothering to special case empty types on the next round. I've already started playing with making type.c_name() work on implicit types - it generates names like '_obj_Foo_wrapper', which won't collide (because we reserved leading underscore for our own use), but also doesn't quite match conventional naming conventions - but as long as it is used only in generated code, it isn't that bad. And with an implicit type directly laid out, I can then just blindly call visit_type_FOO_members(), even for implicit base or variant. The v4 spin of the second half of this series is looking promising... -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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