f51d8fab44
We have two issues with our qapi union layout:
1) Even though the QMP wire format spells the tag 'type', the
C code spells it 'kind', requiring some hacks in the generator.
2) The C struct uses an anonymous union, which places all tag
values in the same namespace as all non-variant members. This
leads to spurious collisions if a tag value matches a non-variant
member's name.
This patch is the front end for a series that converts to a
saner qapi union layout. By the end of the series, we will no
longer have the type/kind mismatch, and all tag values will be
under a named union, which requires clients to access
'obj->u.value' instead of 'obj->value'. But since the
conversion touches a number of files, it is easiest if we
temporarily support BOTH layouts simultaneously.
Given a simple union qapi type:
{ 'union':'Foo', 'data': { 'a':'int', 'b':'bool' } }
make the following changes in generated qapi-types.h:
| struct Foo {
|- FooKind kind;
|- union { /* union tag is @kind */
|+ union {
|+ FooKind kind;
|+ FooKind type;
|+ };
|+ union { /* union tag is @type */
| void *data;
| int64_t a;
| bool b;
|+ union { /* union tag is @type */
|+ void *data;
|+ int64_t a;
|+ bool b;
|+ } u;
| };
| };
Flat unions do not need the anonymous union for the tag member,
as we already fixed that to use the member name instead of 'kind'
back in commit 0f61af3e.
One additional change is needed in qapi.py: check_union() now
needs to check for collisions with 'type' in addition to those
with 'kind'.
Later, when the conversions are complete, we will remove the
duplication hacks, and also drop the check_union() restrictions.
Note, however, that we do not rename the generated enum, which
is still 'FooKind'. A further patch could generate implicit
enums as 'FooType', but while the generator already reserved
the '*Kind' namespace (commit 4dc2e69), there are already QMP
constructs with '*Type' naming, which means changing our
reservation namespace would have lots of churn to C code to
deal with a forced name change.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1445898903-12082-13-git-send-email-eblake@redhat.com>
[Commit message tweaked slightly]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
372 lines
9.8 KiB
Python
372 lines
9.8 KiB
Python
#
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# QAPI types generator
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#
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# Copyright IBM, Corp. 2011
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# Copyright (c) 2013-2015 Red Hat Inc.
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#
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# Authors:
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# Anthony Liguori <aliguori@us.ibm.com>
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# Markus Armbruster <armbru@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2.
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# See the COPYING file in the top-level directory.
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from qapi import *
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def gen_fwd_object_or_array(name):
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return mcgen('''
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typedef struct %(c_name)s %(c_name)s;
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''',
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c_name=c_name(name))
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def gen_array(name, element_type):
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return mcgen('''
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struct %(c_name)s {
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union {
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%(c_type)s value;
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uint64_t padding;
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};
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%(c_name)s *next;
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};
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''',
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c_name=c_name(name), c_type=element_type.c_type())
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def gen_struct_field(name, typ, optional):
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ret = ''
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if optional:
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ret += mcgen('''
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bool has_%(c_name)s;
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''',
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c_name=c_name(name))
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ret += mcgen('''
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%(c_type)s %(c_name)s;
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''',
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c_type=typ.c_type(), c_name=c_name(name))
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return ret
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def gen_struct_fields(local_members, base=None):
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ret = ''
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if base:
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ret += mcgen('''
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/* Members inherited from %(c_name)s: */
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''',
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c_name=base.c_name())
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for memb in base.members:
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ret += gen_struct_field(memb.name, memb.type, memb.optional)
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ret += mcgen('''
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/* Own members: */
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''')
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for memb in local_members:
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ret += gen_struct_field(memb.name, memb.type, memb.optional)
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return ret
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def gen_struct(name, base, members):
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ret = mcgen('''
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struct %(c_name)s {
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''',
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c_name=c_name(name))
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ret += gen_struct_fields(members, base)
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# Make sure that all structs have at least one field; this avoids
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# potential issues with attempting to malloc space for zero-length
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# structs in C, and also incompatibility with C++ (where an empty
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# struct is size 1).
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if not (base and base.members) and not members:
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ret += mcgen('''
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char qapi_dummy_field_for_empty_struct;
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''')
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ret += mcgen('''
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};
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''')
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return ret
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def gen_upcast(name, base):
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# C makes const-correctness ugly. We have to cast away const to let
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# this function work for both const and non-const obj.
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return mcgen('''
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static inline %(base)s *qapi_%(c_name)s_base(const %(c_name)s *obj)
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{
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return (%(base)s *)obj;
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}
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''',
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c_name=c_name(name), base=base.c_name())
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def gen_alternate_qtypes_decl(name):
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return mcgen('''
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extern const int %(c_name)s_qtypes[];
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''',
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c_name=c_name(name))
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def gen_alternate_qtypes(name, variants):
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ret = mcgen('''
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const int %(c_name)s_qtypes[QTYPE_MAX] = {
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''',
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c_name=c_name(name))
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for var in variants.variants:
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qtype = var.type.alternate_qtype()
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assert qtype
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ret += mcgen('''
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[%(qtype)s] = %(enum_const)s,
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''',
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qtype=qtype,
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enum_const=c_enum_const(variants.tag_member.type.name,
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var.name))
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ret += mcgen('''
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};
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''')
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return ret
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def gen_union(name, base, variants):
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ret = mcgen('''
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struct %(c_name)s {
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''',
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c_name=c_name(name))
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if base:
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ret += gen_struct_fields([], base)
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else:
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# TODO As a hack, we emit both 'kind' and 'type'. Ultimately, we
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# want to use only 'type', but the conversion is large enough to
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# require staging over several commits.
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ret += mcgen('''
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union {
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%(c_type)s kind;
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%(c_type)s type;
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};
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''',
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c_type=c_name(variants.tag_member.type.name))
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# TODO As a hack, we emit the union twice, once as an anonymous union
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# and once as a named union. Ultimately, we want to use only the
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# named union version (as it avoids conflicts between tag values as
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# branch names competing with non-variant QMP names), but the conversion
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# is large enough to require staging over several commits.
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tmp = ''
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# FIXME: What purpose does data serve, besides preventing a union that
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# has a branch named 'data'? We use it in qapi-visit.py to decide
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# whether to bypass the switch statement if visiting the discriminator
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# failed; but since we 0-initialize structs, and cannot tell what
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# branch of the union is in use if the discriminator is invalid, there
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# should not be any data leaks even without a data pointer. Or, if
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# 'data' is merely added to guarantee we don't have an empty union,
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# shouldn't we enforce that at .json parse time?
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tmp += mcgen('''
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union { /* union tag is @%(c_name)s */
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void *data;
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''',
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c_name=c_name(variants.tag_member.name))
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for var in variants.variants:
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# Ugly special case for simple union TODO get rid of it
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typ = var.simple_union_type() or var.type
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tmp += mcgen('''
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%(c_type)s %(c_name)s;
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''',
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c_type=typ.c_type(),
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c_name=c_name(var.name))
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ret += tmp
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ret += ' ' + '\n '.join(tmp.split('\n'))
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ret += mcgen('''
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} u;
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};
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};
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''')
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return ret
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def gen_type_cleanup_decl(name):
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ret = mcgen('''
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void qapi_free_%(c_name)s(%(c_name)s *obj);
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''',
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c_name=c_name(name))
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return ret
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def gen_type_cleanup(name):
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ret = mcgen('''
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void qapi_free_%(c_name)s(%(c_name)s *obj)
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{
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QapiDeallocVisitor *qdv;
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Visitor *v;
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if (!obj) {
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return;
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}
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qdv = qapi_dealloc_visitor_new();
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v = qapi_dealloc_get_visitor(qdv);
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visit_type_%(c_name)s(v, &obj, NULL, NULL);
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qapi_dealloc_visitor_cleanup(qdv);
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}
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''',
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c_name=c_name(name))
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return ret
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class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
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def __init__(self):
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self.decl = None
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self.defn = None
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self._fwdecl = None
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self._fwdefn = None
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self._btin = None
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def visit_begin(self, schema):
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self.decl = ''
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self.defn = ''
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self._fwdecl = ''
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self._fwdefn = ''
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self._btin = guardstart('QAPI_TYPES_BUILTIN')
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def visit_end(self):
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self.decl = self._fwdecl + self.decl
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self._fwdecl = None
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self.defn = self._fwdefn + self.defn
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self._fwdefn = None
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# To avoid header dependency hell, we always generate
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# declarations for built-in types in our header files and
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# simply guard them. See also do_builtins (command line
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# option -b).
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self._btin += guardend('QAPI_TYPES_BUILTIN')
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self.decl = self._btin + self.decl
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self._btin = None
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def visit_needed(self, entity):
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# Visit everything except implicit objects
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return not (entity.is_implicit() and
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isinstance(entity, QAPISchemaObjectType))
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def _gen_type_cleanup(self, name):
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self.decl += gen_type_cleanup_decl(name)
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self.defn += gen_type_cleanup(name)
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def visit_enum_type(self, name, info, values, prefix):
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self._fwdecl += gen_enum(name, values, prefix)
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self._fwdefn += gen_enum_lookup(name, values, prefix)
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def visit_array_type(self, name, info, element_type):
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if isinstance(element_type, QAPISchemaBuiltinType):
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self._btin += gen_fwd_object_or_array(name)
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self._btin += gen_array(name, element_type)
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self._btin += gen_type_cleanup_decl(name)
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if do_builtins:
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self.defn += gen_type_cleanup(name)
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else:
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self._fwdecl += gen_fwd_object_or_array(name)
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self.decl += gen_array(name, element_type)
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self._gen_type_cleanup(name)
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def visit_object_type(self, name, info, base, members, variants):
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self._fwdecl += gen_fwd_object_or_array(name)
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if variants:
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assert not members # not implemented
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self.decl += gen_union(name, base, variants)
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else:
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self.decl += gen_struct(name, base, members)
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if base:
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self.decl += gen_upcast(name, base)
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self._gen_type_cleanup(name)
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def visit_alternate_type(self, name, info, variants):
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self._fwdecl += gen_fwd_object_or_array(name)
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self._fwdefn += gen_alternate_qtypes(name, variants)
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self.decl += gen_union(name, None, variants)
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self.decl += gen_alternate_qtypes_decl(name)
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self._gen_type_cleanup(name)
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# If you link code generated from multiple schemata, you want only one
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# instance of the code for built-in types. Generate it only when
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# do_builtins, enabled by command line option -b. See also
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# QAPISchemaGenTypeVisitor.visit_end().
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do_builtins = False
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(input_file, output_dir, do_c, do_h, prefix, opts) = \
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parse_command_line("b", ["builtins"])
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for o, a in opts:
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if o in ("-b", "--builtins"):
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do_builtins = True
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c_comment = '''
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/*
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* deallocation functions for schema-defined QAPI types
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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* Michael Roth <mdroth@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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'''
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h_comment = '''
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/*
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* schema-defined QAPI types
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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'''
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(fdef, fdecl) = open_output(output_dir, do_c, do_h, prefix,
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'qapi-types.c', 'qapi-types.h',
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c_comment, h_comment)
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fdef.write(mcgen('''
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#include "qapi/dealloc-visitor.h"
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#include "%(prefix)sqapi-types.h"
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#include "%(prefix)sqapi-visit.h"
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''',
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prefix=prefix))
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fdecl.write(mcgen('''
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#include <stdbool.h>
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#include <stdint.h>
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#include "qapi/qmp/qobject.h"
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'''))
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schema = QAPISchema(input_file)
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gen = QAPISchemaGenTypeVisitor()
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schema.visit(gen)
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fdef.write(gen.defn)
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fdecl.write(gen.decl)
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close_output(fdef, fdecl)
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