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
This is a dynamic casting macro that, given a QObject type, returns an object as that type or NULL if the object is of a different type (or NULL itself). The macro uses lower-case letters because: 1. There does not seem to be a hard rule on whether qemu macros have to be upper-cased, 2. The current situation in qapi/qmp is inconsistent (compare e.g. QINCREF() vs. qdict_put()), 3. qobject_to() will evaluate its @obj parameter only once, thus it is generally not important to the caller whether it is a macro or not, 4. I prefer it aesthetically. The macro parameter order is chosen with typename first for consistency with other QAPI macros like QAPI_CLONE(), as well as for legibility (read it as "qobject to" type "applied to" obj). Signed-off-by: Max Reitz <mreitz@redhat.com> Message-Id: <20180224154033.29559-3-mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> [eblake: swap parameter order to list type first, avoid clang ubsan warning on QOBJECT(NULL) and container_of(NULL,type,base)] Signed-off-by: Eric Blake <eblake@redhat.com>