unicorn/qemu/scripts
Eric Blake f7d5b1c833
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.

Backports commit bac5429ccb4f41d421ec641b11f1852c8420fdb7 from qemu
2018-02-19 22:12:19 -05:00
..
create_config more cleanup qemu/configure 2017-01-19 14:11:54 +08:00
make_device_config.sh fix file perms 2015-08-28 21:05:38 -07:00
ordereddict.py import 2015-08-21 15:04:50 +08:00
qapi-event.py qapi: Share gen_visit_fields() 2018-02-19 18:41:41 -05:00
qapi-types.py qapi-types: Drop unnedeed ._fwdefn 2018-02-19 21:53:45 -05:00
qapi-visit.py qapi: Fix alternates that accept 'number' but not 'int' 2018-02-19 21:58:10 -05:00
qapi.py qapi: Detect base class loops 2018-02-19 22:12:19 -05:00