By moving the base fields to a QObjectBase_, QObject can be a type
which also has a 'base' field. This allows writing a generic QOBJECT()
macro that will work with any QObject type, including QObject
itself. The container_of() macro ensures that the object to cast has a
QObjectBase_ base field, giving some type safety guarantees. QObject
must have no members but QObjectBase_ base, or else QOBJECT() breaks.
QObjectBase_ is not a typedef and uses a trailing underscore to make
it obvious it is not for normal use and to avoid potential abuse.
Backports commit 3d3eacaeccaab718ea0e2ddaa578bfae9e311c59 from qemu
This generic function (along with its implementations for different
types) determines whether two QObjects are equal.
Backports commit b38dd678a21582e03ecd2dec76ccf8290455628a from qemu
This renders many inclusions of qapi/qmp/q*.h superfluous. They'll be
dropped in the next few commits.
Backports commit 9f5c734d591e26186a71f9e36d752f4798df3672 from qemu
The QObject hierarchy is small enough, and unlikely to grow further
(since we only use it to map to JSON and already cover all JSON
types), that we can simplify things by not tracking a separate
vtable, but just inline the code element of the vtable QType
directly into QObject (renamed to type), and track a separate array
of destroy functions. We can drop qnull_destroy_obj() in the
process.
The remaining QObject subclasses must export their destructor.
This also has the nice benefit of moving the typename 'QType'
out of the way, so that the next patch can repurpose it for a
nicer name for 'qtype_code'.
The various objects are still the same size (so no change in cache
line pressure), but now have less indirection (although I didn't
bother benchmarking to see if there is a noticeable speedup, as
we don't have hard evidence that this was in a performance hotspot
in the first place).
A future patch could drop the refcnt size to 32 bits for a smaller
struct on 64-bit architectures, if desired (we have limits on the
largest JSON that we are willing to parse, and will probably never
need to take full advantage of a 64-bit refcnt).
Backports commit 55e1819c509b3d9c10a54678b9c585bbda13889e from qemu
We require a C99 compiler, so let's use 'bool' instead of 'int'
when dealing with boolean values. There are few enough clients
to fix them all in one pass.
Backports commit fc48ffc39ed1060856475e4320d5896f26c945e8 from qemu
