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2ee6c960ee
Previously, working with alternates required two lookup arrays
and some indirection: for type Foo, we created Foo_qtypes[]
which maps each qtype to a value of the generated FooKind enum,
then look up that value in FooKind_lookup[] like we do for other
union types.
This has a couple of subtle bugs. First, the generator was
creating a call with a parameter '(int *) &(*obj)->type' where
type is an enum type; this is unsafe if the compiler chooses
to store the enum type in a different size than int, where
assigning through the wrong size pointer can corrupt data or
cause a SIGBUS.
Related bug, not not fixed in this patch: qapi-visit.py's
gen_visit_enum() generates a cast of its enum * argument to
int *. Marked FIXME.
Second, since the values of the FooKind enum start at zero, all
entries of the Foo_qtypes[] array that were not explicitly
initialized will map to the same branch of the union as the
first member of the alternate, rather than triggering a desired
failure in visit_get_next_type(). Fortunately, the bug seldom
bites; the very next thing the input visitor does is try to
parse the incoming JSON with the wrong parser, which normally
fails; the output visitor is not used with a C struct in that
state, and the dealloc visitor has nothing to clean up (so
there is no leak).
However, the second bug IS observable in one case: parsing an
integer causes unusual behavior in an alternate that contains
at least a 'number' member but no 'int' member, because the
'number' parser accepts QTYPE_QINT in addition to the expected
QTYPE_QFLOAT (that is, since 'int' is not a member, the type
QTYPE_QINT accidentally maps to FooKind 0; if this enum value
is the 'number' branch the integer parses successfully, but if
the 'number' branch is not first, some other branch tries to
parse the integer and rejects it). A later patch will worry
about fixing alternates to always parse all inputs that a
non-alternate 'number' would accept, for now this is still
marked FIXME in the updated test-qmp-input-visitor.c, to
merely point out that new undesired behavior of 'ans' matches
the existing undesired behavior of 'asn'.
This patch fixes the default-initialization bug by deleting the
indirection, and modifying get_next_type() to directly assign a
QTypeCode parameter. This in turn fixes the type-casting bug,
as we are no longer casting a pointer to enum to a questionable
size. There is no longer a need to generate an implicit FooKind
enum associated with the alternate type (since the QMP wire
format never uses the stringized counterparts of the C union
member names). Since the updated visit_get_next_type() does not
know which qtypes are expected, the generated visitor is
modified to generate an error statement if an unexpected type is
encountered.
Callers now have to know the QTYPE_* mapping when looking at the
discriminator; but so far, only the testsuite was even using the
C struct of an alternate types. I considered the possibility of
keeping the internal enum FooKind, but initialized differently
than most generated arrays, as in:
typedef enum FooKind {
FOO_KIND_A = QTYPE_QDICT,
FOO_KIND_B = QTYPE_QINT,
} FooKind;
to create nicer aliases for knowing when to use foo->a or foo->b
when inspecting foo->type; but it turned out to add too much
complexity, especially without a client.
There is a user-visible side effect to this change, but I
consider it to be an improvement. Previously,
the invalid QMP command:
{"execute":"blockdev-add", "arguments":{"options":
{"driver":"raw", "id":"a", "file":true}}}
failed with:
{"error": {"class": "GenericError",
"desc": "Invalid parameter type for 'file', expected: QDict"}}
(visit_get_next_type() succeeded, and the error comes from the
visit_type_BlockdevOptions() expecting {}; there is no mention of
the fact that a string would also work). Now it fails with:
{"error": {"class": "GenericError",
"desc": "Invalid parameter type for 'file', expected: BlockdevRef"}}
(the error when the next type doesn't match any expected types for
the overall alternate).
Backports commit 0426d53c6530606bf7641b83f2b755fe61c280ee from qemu
75 lines
3.1 KiB
C
75 lines
3.1 KiB
C
/*
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* Core Definitions for QAPI Visitor implementations
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*
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* Copyright (C) 2012-2016 Red Hat, Inc.
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*
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* Author: Paolo Bonizni <pbonzini@redhat.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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#ifndef QAPI_VISITOR_IMPL_H
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#define QAPI_VISITOR_IMPL_H
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#include "qapi/error.h"
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#include "qapi/visitor.h"
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struct Visitor
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{
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/* Must be set */
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void (*start_struct)(Visitor *v, void **obj, const char *kind,
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const char *name, size_t size, Error **errp);
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void (*end_struct)(Visitor *v, Error **errp);
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void (*start_implicit_struct)(Visitor *v, void **obj, size_t size,
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Error **errp);
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void (*end_implicit_struct)(Visitor *v);
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void (*start_list)(Visitor *v, const char *name, Error **errp);
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GenericList *(*next_list)(Visitor *v, GenericList **list);
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void (*end_list)(Visitor *v);
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void (*type_enum)(Visitor *v, int *obj, const char * const strings[],
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const char *kind, const char *name, Error **errp);
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/* May be NULL; only needed for input visitors. */
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void (*get_next_type)(Visitor *v, QType *type,
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const char *name, Error **errp);
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/* Must be set. */
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void (*type_int64)(Visitor *v, int64_t *obj, const char *name,
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Error **errp);
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/* Must be set. */
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void (*type_uint64)(Visitor *v, uint64_t *obj, const char *name,
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Error **errp);
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/* Optional; fallback is type_uint64(). */
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void (*type_size)(Visitor *v, uint64_t *obj, const char *name,
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Error **errp);
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/* Must be set. */
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void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);
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void (*type_str)(Visitor *v, char **obj, const char *name, Error **errp);
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void (*type_number)(Visitor *v, double *obj, const char *name,
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Error **errp);
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void (*type_any)(Visitor *v, QObject **obj, const char *name,
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Error **errp);
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/* May be NULL */
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void (*optional)(Visitor *v, bool *present, const char *name,
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Error **errp);
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void (*type_uint8)(Visitor *v, uint8_t *obj, const char *name, Error **errp);
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void (*type_uint16)(Visitor *v, uint16_t *obj, const char *name, Error **errp);
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void (*type_uint32)(Visitor *v, uint32_t *obj, const char *name, Error **errp);
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void (*type_int8)(Visitor *v, int8_t *obj, const char *name, Error **errp);
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void (*type_int16)(Visitor *v, int16_t *obj, const char *name, Error **errp);
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void (*type_int32)(Visitor *v, int32_t *obj, const char *name, Error **errp);
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bool (*start_union)(Visitor *v, bool data_present, Error **errp);
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void (*end_union)(Visitor *v, bool data_present, Error **errp);
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};
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void input_type_enum(Visitor *v, int *obj, const char * const strings[],
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const char *kind, const char *name, Error **errp);
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void output_type_enum(Visitor *v, int *obj, const char * const strings[],
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const char *kind, const char *name, Error **errp);
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#endif
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