qemu-patch-raspberry4/tests/qapi-schema/flat-union-empty.out

object :empty
object Base
    member type: Empty optional=False
enum Empty []
enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
    prefix QTYPE
object Union
    base Base
    tag type
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			`object :empty`
			`object Base`
			`member type: Empty optional=False`
			`enum Empty []`
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			`enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']`
			`prefix QTYPE`
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			`object Union`
			`base Base`
			`tag type`