qemu/tests/qapi-schema/base-cycle-direct.json

# we reject a loop in base classes
{ 'struct': 'Loopy', 'base': 'Loopy', 'data': {} }
qapi: Detect base class loops It should be fairly obvious that qapi base classes need to form an acyclic graph, since QMP cannot specify the same key more than once, while base classes are included as flat members alongside other members added by the child. But the old check_member_clash() parser function was not prepared to check for this, and entered an infinite recursion (at least until Python gives up, complaining about nesting too deep). Now that check_member_clash() has been recently removed, attempts at self-inheritance trigger an assertion failure introduced by commit ac88219a. The obvious fix is to turn the assertion into a conditional. This patch includes both the tests (base-cycle-direct and base-cycle-indirect) and the fix, since the .err file output for the unfixed case is not useful (particularly when it was warning about unbounded recursion, as that limit may be platform-specific). We don't need to worry about cycles in flat unions (neither the base type nor the type of a variant can be a union) nor in alternates (alternate branches cannot themselves be an alternate). But if we later allow a union type as a variant, we will still be okay, as QAPISchemaObjectTypeVariants.check() triggers the same QAPISchemaObjectType.check() that will detect any loops. Likewise, we need not worry about the case of diamond inheritance where the same class is used for a flat union base class and one of its variants; either both uses will introduce a collision in trying to insert the same member name twice, or the shared type is empty and changes nothing. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1449033659-25497-16-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> 2015-12-02 08:20:59 +03:00			`# we reject a loop in base classes`
			`{ 'struct': 'Loopy', 'base': 'Loopy', 'data': {} }`