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

object :empty
object Union
    member type: UnionKind optional=False
enum UnionKind []
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 Union`
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			`member type: UnionKind optional=False`
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			`enum UnionKind []`