qapi: Add tests for empty unions
The documentation claims that alternates are useful for
allowing two or more types, although nothing enforces this.
Meanwhile, it is silent on whether empty unions are allowed.
In practice, the generated code will compile, in part because
we have a 'void *data' branch; but attempting to visit such a
type will cause an abort(). While there's no technical reason
that a degenerate union could not be made to work, it's harder
to justify the time spent in chasing known (the current
abort() during visit) and unknown corner cases, than it would
be to just outlaw them. A future patch will probably take the
approach of forbidding them; in the meantime, we can at least
add testsuite coverage to make it obvious where things stand.
In addition to adding tests to expose the problems, we also
need to adjust existing tests that are meant to test something
else, but which could fail for the wrong reason if we reject
degenerate alternates/unions.
Note that empty structs are explicitly supported (for example,
right now they are the only way to specify that one branch of a
flat union adds no additional members), and empty enums are
covered by the testsuite as working (even if they do not seem
to have much use).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1443565276-4535-8-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-09-30 00:21:05 +02:00
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object :empty
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qapi: Convert QType into QAPI built-in enum type
What's more meta than using qapi to define qapi? :)
Convert QType into a full-fledged[*] builtin qapi enum type, so
that a subsequent patch can then use it as the discriminator
type of qapi alternate types. Fortunately, the judicious use of
'prefix' in the qapi definition avoids churn to the spelling of
the enum constants.
To avoid circular definitions, we have to flip the order of
inclusion between "qobject.h" vs. "qapi-types.h". Back in commit
28770e0, we had the latter include the former, so that we could
use 'QObject *' for our implementation of 'any'. But that usage
also works with only a forward declaration, whereas the
definition of QObject requires QType to be a complete type.
[*] The type has to be builtin, rather than declared in
qapi/common.json, because we want to use it for alternates even
when common.json is not included. But since it is the first
builtin enum type, we have to add special cases to qapi-types
and qapi-visit to only emit definitions once, even when two
qapi files are being compiled into the same binary (the way we
already handled builtin list types like 'intList'). We may
need to revisit how multiple qapi files share common types,
but that's a project for another day.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1449033659-25497-4-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-12-02 06:20:47 +01:00
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enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
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prefix QTYPE
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qapi: Add tests for empty unions
The documentation claims that alternates are useful for
allowing two or more types, although nothing enforces this.
Meanwhile, it is silent on whether empty unions are allowed.
In practice, the generated code will compile, in part because
we have a 'void *data' branch; but attempting to visit such a
type will cause an abort(). While there's no technical reason
that a degenerate union could not be made to work, it's harder
to justify the time spent in chasing known (the current
abort() during visit) and unknown corner cases, than it would
be to just outlaw them. A future patch will probably take the
approach of forbidding them; in the meantime, we can at least
add testsuite coverage to make it obvious where things stand.
In addition to adding tests to expose the problems, we also
need to adjust existing tests that are meant to test something
else, but which could fail for the wrong reason if we reject
degenerate alternates/unions.
Note that empty structs are explicitly supported (for example,
right now they are the only way to specify that one branch of a
flat union adds no additional members), and empty enums are
covered by the testsuite as working (even if they do not seem
to have much use).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1443565276-4535-8-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-09-30 00:21:05 +02:00
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object Union
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qapi: Track simple union tag in object.local_members
We were previously creating all unions with an empty list for
local_members. However, it will make it easier to unify struct
and union generation if we include the generated tag member in
local_members. That way, we can have a common code pattern:
visit the base (if any), visit the local members (if any), visit
the variants (if any). The local_members of a flat union
remains empty (because the discriminator is already visited as
part of the base). Then, by visiting tag_member.check() during
AlternateType.check(), we no longer need to call it during
Variants.check().
The various front end entities now exist as follows:
struct: optional base, optional local_members, no variants
simple union: no base, one-element local_members, variants with tag_member
from local_members
flat union: base, no local_members, variants with tag_member from base
alternate: no base, no local_members, variants
With the new local members, we require a bit of finesse to
avoid assertions in the clients.
No change to generated code.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1447836791-369-2-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-18 09:52:36 +01:00
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member type: UnionKind optional=False
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qapi: Add tests for empty unions
The documentation claims that alternates are useful for
allowing two or more types, although nothing enforces this.
Meanwhile, it is silent on whether empty unions are allowed.
In practice, the generated code will compile, in part because
we have a 'void *data' branch; but attempting to visit such a
type will cause an abort(). While there's no technical reason
that a degenerate union could not be made to work, it's harder
to justify the time spent in chasing known (the current
abort() during visit) and unknown corner cases, than it would
be to just outlaw them. A future patch will probably take the
approach of forbidding them; in the meantime, we can at least
add testsuite coverage to make it obvious where things stand.
In addition to adding tests to expose the problems, we also
need to adjust existing tests that are meant to test something
else, but which could fail for the wrong reason if we reject
degenerate alternates/unions.
Note that empty structs are explicitly supported (for example,
right now they are the only way to specify that one branch of a
flat union adds no additional members), and empty enums are
covered by the testsuite as working (even if they do not seem
to have much use).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1443565276-4535-8-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-09-30 00:21:05 +02:00
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enum UnionKind []
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