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From d177d54c7ca08f3fff5824d69d4e66ca05a4eaf8 Mon Sep 17 00:00:00 2001
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From: Markus Armbruster <armbru@redhat.com>
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Date: Mon, 18 Jun 2018 08:43:09 +0200
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Subject: [PATCH 011/268] qobject: Ensure base is at offset 0
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Markus Armbruster <armbru@redhat.com>
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Message-id: <20180618084330.30009-3-armbru@redhat.com>
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Patchwork-id: 80724
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O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 02/23] qobject: Ensure base is at offset 0
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Bugzilla: 1557995
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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From: Marc-André Lureau <marcandre.lureau@redhat.com>
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All QObject types have the base QObject as their first field. This
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allows the simplification of qobject_to().
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Message-Id: <20180419150145.24795-2-marcandre.lureau@redhat.com>
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Reviewed-by: Markus Armbruster <armbru@redhat.com>
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[Commit message paragraph on type casts dropped, to avoid giving the
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impression type casting would be okay]
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Signed-off-by: Markus Armbruster <armbru@redhat.com>
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(cherry picked from commit 7ee9edfdb117da47c86c9764d90f0be11a648666)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 include/qapi/qmp/qobject.h | 5 ++---
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 qobject/qobject.c          | 9 +++++++++
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 2 files changed, 11 insertions(+), 3 deletions(-)
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diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h
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index e022707..5206ff9 100644
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--- a/include/qapi/qmp/qobject.h
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+++ b/include/qapi/qmp/qobject.h
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@@ -61,9 +61,8 @@ struct QObject {
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 QEMU_BUILD_BUG_MSG(QTYPE__MAX != 7,
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                    "The QTYPE_CAST_TO_* list needs to be extended");
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-#define qobject_to(type, obj) ({ \
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-    QObject *_tmp = qobject_check_type(obj, glue(QTYPE_CAST_TO_, type)); \
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-    _tmp ? container_of(_tmp, type, base) : (type *)NULL; })
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+#define qobject_to(type, obj)                                       \
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+    ((type *)qobject_check_type(obj, glue(QTYPE_CAST_TO_, type)))
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 /* Initialize an object to default values */
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 static inline void qobject_init(QObject *obj, QType type)
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diff --git a/qobject/qobject.c b/qobject/qobject.c
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index 23600aa..87649c5 100644
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--- a/qobject/qobject.c
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+++ b/qobject/qobject.c
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@@ -16,6 +16,15 @@
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 #include "qapi/qmp/qlist.h"
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 #include "qapi/qmp/qstring.h"
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+QEMU_BUILD_BUG_MSG(
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+    offsetof(QNull, base) != 0 ||
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+    offsetof(QNum, base) != 0 ||
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+    offsetof(QString, base) != 0 ||
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+    offsetof(QDict, base) != 0 ||
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+    offsetof(QList, base) != 0 ||
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+    offsetof(QBool, base) != 0,
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+    "base qobject must be at offset 0");
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+
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 static void (*qdestroy[QTYPE__MAX])(QObject *) = {
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     [QTYPE_NONE] = NULL,               /* No such object exists */
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     [QTYPE_QNULL] = NULL,              /* qnull_ is indestructible */
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-- 
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1.8.3.1
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