| Message ID | 1455778109-6278-11-git-send-email-eblake@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Eric Blake <eblake@redhat.com> writes: > Right now, we emit the branches of union types as a boxed pointer, > and it suffices to have a forward declaration of the type. However, > a future patch will swap things to directly use the branch type, > instead of hiding it behind a pointer. For this to work, the > compiler needs the full definition of the type, not just a forward > declaration, prior to the union that is including the branch type. > This patch just adds topological sorting to hoist all types > mentioned in a branch of a union to be fully declared before the > union itself. The sort is always possible, because we do not > allow circular union types that include themselves as a direct > branch When a patch makes a "can't happen" claim, I normally ask for assertions to make sure we go down in flames should it happen anyway. But in this case, the C compiler will shoot us down then, and that'll do nicely. > (it is, however, still possible to include a branch type > that itself has a pointer to the union, for a type that can > indirectly recursively nest itself - that remains safe, because > that the member of the branch type will remain a pointer, and the > QMP representation of such a type adds another {} for each recurring > layer of the union type). > > Signed-off-by: Eric Blake <eblake@redhat.com>
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py index 83f230a..6ea0ae6 100644 --- a/scripts/qapi-types.py +++ b/scripts/qapi-types.py @@ -2,7 +2,7 @@ # QAPI types generator # # Copyright IBM, Corp. 2011 -# Copyright (c) 2013-2015 Red Hat Inc. +# Copyright (c) 2013-2016 Red Hat Inc. # # Authors: # Anthony Liguori <aliguori@us.ibm.com> @@ -14,6 +14,11 @@ from qapi import * +# variants must be emitted before their container; track what has already +# been output +objects_seen = set() + + def gen_fwd_object_or_array(name): return mcgen(''' @@ -49,11 +54,23 @@ def gen_struct_fields(members): def gen_object(name, base, members, variants): - ret = mcgen(''' + if name in objects_seen: + return '' + objects_seen.add(name) + + ret = '' + if variants: + for v in variants.variants: + if (isinstance(v.type, QAPISchemaObjectType) and + not v.type.is_implicit()): + ret += gen_object(v.type.name, v.type.base, + v.type.local_members, v.type.variants) + + ret += mcgen(''' struct %(c_name)s { ''', - c_name=c_name(name)) + c_name=c_name(name)) if base: ret += mcgen('''
Right now, we emit the branches of union types as a boxed pointer, and it suffices to have a forward declaration of the type. However, a future patch will swap things to directly use the branch type, instead of hiding it behind a pointer. For this to work, the compiler needs the full definition of the type, not just a forward declaration, prior to the union that is including the branch type. This patch just adds topological sorting to hoist all types mentioned in a branch of a union to be fully declared before the union itself. The sort is always possible, because we do not allow circular union types that include themselves as a direct branch (it is, however, still possible to include a branch type that itself has a pointer to the union, for a type that can indirectly recursively nest itself - that remains safe, because that the member of the branch type will remain a pointer, and the QMP representation of such a type adds another {} for each recurring layer of the union type). Signed-off-by: Eric Blake <eblake@redhat.com> --- v11: pep8 cleanup v10: new patch --- scripts/qapi-types.py | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)