Message ID | 1457571335-10938-6-git-send-email-eblake@redhat.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Eric Blake <eblake@redhat.com> writes: > We already have several places that want to visit all the members > of an implicit object within a larger context (simple union variant, > event with anonymous data, command with anonymous arguments struct); > and will be adding another one soon (the ability to declare an > anonymous base for a flat union). Having a C struct declared for > these implicit types, along with a visit_type_FOO_members() helper > function, will make for fewer special cases in our generator. > > We do not, however, need qapi_free_FOO() or visit_type_FOO() > functions for implicit types, because they should not be used > directly outside of the generated code. This is done by adding a > conditional in visit_object_type() for both qapi-types.py and > qapi-visit.py based on the object name. The comparison of > "name.startswith('q_')" is a bit hacky (it's basically duplicating > what .is_implicit() already uses), but beats changing the signature > of the visit_object_type() callback to pass a new 'implicit' flag. > The hack should be temporary: we are considering adding a future > patch that consolidates the narrow visit_object_type() and > visit_object_type_flat() [with different pieces already broken out] > into a broader visit_object_type() [where the visitor can query the > type object directly]. > > Also, now that we WANT to output C code for implicits, we have to > change the condition in the visit_needed() filter. We have to > special-case 'q_empty' in that filter as something that does not > get output: because it is a built-in type, it would be emitted in > multiple files (the main qapi-types.h and in qga-qapi-types.h) > causing compilation failure due to redefinition. But since it > has no members, it's easier to just avoid an attempt to visit > that particular type. Not just easier. ':empty' is a genuinely internal thing so far (it exists only to make qapi-introspect.py simpler), and generating C for it would be weird. > The patch relies on the changed naming of implicit types in the > previous patch. It is a bit unfortunate that the generated struct > names and visit_type_FOO_members() don't match normal naming > conventions, but it's not too bad, since they will only be used in > generated code. > > The generated code grows substantially in size: the implicit > '-wrapper' types must be emitted in qapi-types.h before any union > can include an unboxed member of that type. Arguably, the '-args' > types could be emitted in a private header for just qapi-visit.c > and qmp-marshal.c, rather than polluting qapi-types.h; but adding > complexity to the generator to split the output location according > to role doesn't seem worth the maintenance costs. Another idea > for a later patch would be reworking error.h to not need to > include all of qapi-types.h. I got that in my tree. If it goes in before this patch, the last sentence should be dropped. > Signed-off-by: Eric Blake <eblake@redhat.com> > > --- > v5: rebase onto different naming scheme, document future improvements > v4: new patch > --- > scripts/qapi.py | 2 -- > scripts/qapi-types.py | 14 ++++++++------ > scripts/qapi-visit.py | 20 ++++++++++---------- > 3 files changed, 18 insertions(+), 18 deletions(-) > > diff --git a/scripts/qapi.py b/scripts/qapi.py > index f6701f5..96fb216 100644 > --- a/scripts/qapi.py > +++ b/scripts/qapi.py > @@ -1000,7 +1000,6 @@ class QAPISchemaObjectType(QAPISchemaType): > return self.name.startswith('q_') > > def c_name(self): > - assert not self.is_implicit() > return QAPISchemaType.c_name(self) > > def c_type(self): > @@ -1008,7 +1007,6 @@ class QAPISchemaObjectType(QAPISchemaType): > return c_name(self.name) + pointer_suffix > > def c_unboxed_type(self): > - assert not self.is_implicit() > return c_name(self.name) > > def json_type(self): > diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py > index f194bea..107eabe 100644 > --- a/scripts/qapi-types.py > +++ b/scripts/qapi-types.py > @@ -61,8 +61,7 @@ def gen_object(name, base, members, variants): > ret = '' > if variants: > for v in variants.variants: > - if (isinstance(v.type, QAPISchemaObjectType) and > - not v.type.is_implicit()): > + if isinstance(v.type, QAPISchemaObjectType): > ret += gen_object(v.type.name, v.type.base, > v.type.local_members, v.type.variants) > > @@ -197,9 +196,8 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor): > self._btin = None > > def visit_needed(self, entity): > - # Visit everything except implicit objects > - return not (entity.is_implicit() and > - isinstance(entity, QAPISchemaObjectType)) > + # Visit everything except the special empty builtin > + return entity.name != 'q_empty' > > def _gen_type_cleanup(self, name): > self.decl += gen_type_cleanup_decl(name) Before: we visit all types except for implicit object types in "def before use" order. visit_needed() filters out implicit object types. gen_object() sorts by recursing, but filters out non-object types and implicit object types. Note the shared "filters out implicit object types" part. After: we visit all types escept for the empty type in "def before use" order. visit_needed() filters out the empty type. gen_object filters out non-object types. It lost its shared part. If we somehow recurse into the empty type, we visit it. Oops. Actually, we overcomplicated things. visit_needed() exists so we can filter out different kinds of entities in one condition. Really convenient in qapi-introspect.py. But if you want to filter out just one kind (here: object types), like we do here, it's simpler to filter in that kind's visit_ method (here: visit_object_type(). More efficient, too, but that doesn't matter. Since we recurse, we need to additionally filter there. An easy way to do that would be to start with objects_seen set to set(schema.the_empty_object_type) instead of set(). > @@ -233,7 +231,11 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor): > self.decl += gen_object(name, base, members, variants) > if base: > self.decl += gen_upcast(name, base) > - self._gen_type_cleanup(name) > + # FIXME Worth changing the visitor signature, so we could > + # directly use rather than repeat type.is_implicit()? Nitpick: this is a TODO, because it's not about fixing something that's broken. > + if not name.startswith('q_'): > + # implicit types won't be directly allocated/freed > + self._gen_type_cleanup(name) > > def visit_alternate_type(self, name, info, variants): > self._fwdecl += gen_fwd_object_or_array(name) > diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py > index a712e9a..c486aaa 100644 > --- a/scripts/qapi-visit.py > +++ b/scripts/qapi-visit.py > @@ -215,13 +215,11 @@ out: > > > def gen_visit_object(name, base, members, variants): > - ret = gen_visit_object_members(name, base, members, variants) > - See visit_object_type() below. > # FIXME: if *obj is NULL on entry, and visit_start_struct() assigns to > # *obj, but then visit_type_FOO_members() fails, we should clean up *obj > # rather than leaving it non-NULL. As currently written, the caller must > # call qapi_free_FOO() to avoid a memory leak of the partial FOO. > - ret += mcgen(''' > + return mcgen(''' > > void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp) > { > @@ -245,8 +243,6 @@ out: > ''', > c_name=c_name(name)) > > - return ret > - > > class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): > def __init__(self): > @@ -269,9 +265,8 @@ class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): > self._btin = None > > def visit_needed(self, entity): > - # Visit everything except implicit objects > - return not (entity.is_implicit() and > - isinstance(entity, QAPISchemaObjectType)) > + # Visit everything except the special empty builtin > + return entity.name != 'q_empty' As in qapi-types.py, visit_needed() isn't necessary even before the patch. > def visit_enum_type(self, name, info, values, prefix): > # Special case for our lone builtin enum type > @@ -297,8 +292,13 @@ class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): > > def visit_object_type(self, name, info, base, members, variants): > self.decl += gen_visit_members_decl(name) > - self.decl += gen_visit_decl(name) > - self.defn += gen_visit_object(name, base, members, variants) > + self.defn += gen_visit_object_members(name, base, members, variants) Moved from gen_visit_object(), the rest can be called conditionally: > + # FIXME Worth changing the visitor signature, so we could > + # directly use rather than repeat type.is_implicit()? > + if not name.startswith('q_'): > + # only explicit types need an allocating visit > + self.decl += gen_visit_decl(name) > + self.defn += gen_visit_object(name, base, members, variants) > > def visit_alternate_type(self, name, info, variants): > self.decl += gen_visit_decl(name) Okay.
diff --git a/scripts/qapi.py b/scripts/qapi.py index f6701f5..96fb216 100644 --- a/scripts/qapi.py +++ b/scripts/qapi.py @@ -1000,7 +1000,6 @@ class QAPISchemaObjectType(QAPISchemaType): return self.name.startswith('q_') def c_name(self): - assert not self.is_implicit() return QAPISchemaType.c_name(self) def c_type(self): @@ -1008,7 +1007,6 @@ class QAPISchemaObjectType(QAPISchemaType): return c_name(self.name) + pointer_suffix def c_unboxed_type(self): - assert not self.is_implicit() return c_name(self.name) def json_type(self): diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py index f194bea..107eabe 100644 --- a/scripts/qapi-types.py +++ b/scripts/qapi-types.py @@ -61,8 +61,7 @@ def gen_object(name, base, members, variants): ret = '' if variants: for v in variants.variants: - if (isinstance(v.type, QAPISchemaObjectType) and - not v.type.is_implicit()): + if isinstance(v.type, QAPISchemaObjectType): ret += gen_object(v.type.name, v.type.base, v.type.local_members, v.type.variants) @@ -197,9 +196,8 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor): self._btin = None def visit_needed(self, entity): - # Visit everything except implicit objects - return not (entity.is_implicit() and - isinstance(entity, QAPISchemaObjectType)) + # Visit everything except the special empty builtin + return entity.name != 'q_empty' def _gen_type_cleanup(self, name): self.decl += gen_type_cleanup_decl(name) @@ -233,7 +231,11 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor): self.decl += gen_object(name, base, members, variants) if base: self.decl += gen_upcast(name, base) - self._gen_type_cleanup(name) + # FIXME Worth changing the visitor signature, so we could + # directly use rather than repeat type.is_implicit()? + if not name.startswith('q_'): + # implicit types won't be directly allocated/freed + self._gen_type_cleanup(name) def visit_alternate_type(self, name, info, variants): self._fwdecl += gen_fwd_object_or_array(name) diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py index a712e9a..c486aaa 100644 --- a/scripts/qapi-visit.py +++ b/scripts/qapi-visit.py @@ -215,13 +215,11 @@ out: def gen_visit_object(name, base, members, variants): - ret = gen_visit_object_members(name, base, members, variants) - # FIXME: if *obj is NULL on entry, and visit_start_struct() assigns to # *obj, but then visit_type_FOO_members() fails, we should clean up *obj # rather than leaving it non-NULL. As currently written, the caller must # call qapi_free_FOO() to avoid a memory leak of the partial FOO. - ret += mcgen(''' + return mcgen(''' void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp) { @@ -245,8 +243,6 @@ out: ''', c_name=c_name(name)) - return ret - class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): def __init__(self): @@ -269,9 +265,8 @@ class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): self._btin = None def visit_needed(self, entity): - # Visit everything except implicit objects - return not (entity.is_implicit() and - isinstance(entity, QAPISchemaObjectType)) + # Visit everything except the special empty builtin + return entity.name != 'q_empty' def visit_enum_type(self, name, info, values, prefix): # Special case for our lone builtin enum type @@ -297,8 +292,13 @@ class QAPISchemaGenVisitVisitor(QAPISchemaVisitor): def visit_object_type(self, name, info, base, members, variants): self.decl += gen_visit_members_decl(name) - self.decl += gen_visit_decl(name) - self.defn += gen_visit_object(name, base, members, variants) + self.defn += gen_visit_object_members(name, base, members, variants) + # FIXME Worth changing the visitor signature, so we could + # directly use rather than repeat type.is_implicit()? + if not name.startswith('q_'): + # only explicit types need an allocating visit + self.decl += gen_visit_decl(name) + self.defn += gen_visit_object(name, base, members, variants) def visit_alternate_type(self, name, info, variants): self.decl += gen_visit_decl(name)
We already have several places that want to visit all the members of an implicit object within a larger context (simple union variant, event with anonymous data, command with anonymous arguments struct); and will be adding another one soon (the ability to declare an anonymous base for a flat union). Having a C struct declared for these implicit types, along with a visit_type_FOO_members() helper function, will make for fewer special cases in our generator. We do not, however, need qapi_free_FOO() or visit_type_FOO() functions for implicit types, because they should not be used directly outside of the generated code. This is done by adding a conditional in visit_object_type() for both qapi-types.py and qapi-visit.py based on the object name. The comparison of "name.startswith('q_')" is a bit hacky (it's basically duplicating what .is_implicit() already uses), but beats changing the signature of the visit_object_type() callback to pass a new 'implicit' flag. The hack should be temporary: we are considering adding a future patch that consolidates the narrow visit_object_type() and visit_object_type_flat() [with different pieces already broken out] into a broader visit_object_type() [where the visitor can query the type object directly]. Also, now that we WANT to output C code for implicits, we have to change the condition in the visit_needed() filter. We have to special-case 'q_empty' in that filter as something that does not get output: because it is a built-in type, it would be emitted in multiple files (the main qapi-types.h and in qga-qapi-types.h) causing compilation failure due to redefinition. But since it has no members, it's easier to just avoid an attempt to visit that particular type. The patch relies on the changed naming of implicit types in the previous patch. It is a bit unfortunate that the generated struct names and visit_type_FOO_members() don't match normal naming conventions, but it's not too bad, since they will only be used in generated code. The generated code grows substantially in size: the implicit '-wrapper' types must be emitted in qapi-types.h before any union can include an unboxed member of that type. Arguably, the '-args' types could be emitted in a private header for just qapi-visit.c and qmp-marshal.c, rather than polluting qapi-types.h; but adding complexity to the generator to split the output location according to role doesn't seem worth the maintenance costs. Another idea for a later patch would be reworking error.h to not need to include all of qapi-types.h. Signed-off-by: Eric Blake <eblake@redhat.com> --- v5: rebase onto different naming scheme, document future improvements v4: new patch --- scripts/qapi.py | 2 -- scripts/qapi-types.py | 14 ++++++++------ scripts/qapi-visit.py | 20 ++++++++++---------- 3 files changed, 18 insertions(+), 18 deletions(-)