unicorn/qemu/qobject/qnull.c

/*
 * QNull
 *
 * Copyright (C) 2015 Red Hat, Inc.
 *
 * Authors:
 *  Markus Armbruster <armbru@redhat.com>
 *
 * This work is licensed under the terms of the GNU LGPL, version 2.1
 * or later.  See the COPYING.LIB file in the top-level directory.
 */

#include "qemu-common.h"
#include "qapi/qmp/qobject.h"

QObject qnull_ = {
    QTYPE_QNULL,
    1,
};
qobject: Add a special null QObject I'm going to fix the JSON parser to recognize null. The obvious representation of JSON null as (QObject *)NULL doesn't work, because the parser already uses it as an error value. Perhaps we should change it to free NULL for null, but that's more than I can do right now. Create a special null QObject instead. The existing QDict, QList, and QString all represent something that is a pointer in C and could therefore be associated with NULL. But right now, all three of these sub-types are always non-null once created, so the new null sentinel object is intentionally unrelated to them. Backports commit 481b002cc81ed7fc7b06e32e9d4d495d81739d14 from qemu 2018-02-20 03:22:11 +01:00			`/*`
			`* QNull`
			`*`
			`* Copyright (C) 2015 Red Hat, Inc.`
			`*`
			`* Authors:`
			`* Markus Armbruster <armbru@redhat.com>`
			`*`
			`* This work is licensed under the terms of the GNU LGPL, version 2.1`
			`* or later. See the COPYING.LIB file in the top-level directory.`
			`*/`

			`#include "qemu-common.h"`
			`#include "qapi/qmp/qobject.h"`

			`QObject qnull_ = {`
qobject: Simplify QObject 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 2018-02-20 03:34:54 +01:00			`QTYPE_QNULL,`
qobject: Add a special null QObject I'm going to fix the JSON parser to recognize null. The obvious representation of JSON null as (QObject *)NULL doesn't work, because the parser already uses it as an error value. Perhaps we should change it to free NULL for null, but that's more than I can do right now. Create a special null QObject instead. The existing QDict, QList, and QString all represent something that is a pointer in C and could therefore be associated with NULL. But right now, all three of these sub-types are always non-null once created, so the new null sentinel object is intentionally unrelated to them. Backports commit 481b002cc81ed7fc7b06e32e9d4d495d81739d14 from qemu 2018-02-20 03:22:11 +01:00			`1,`
			`};`