From: Eric Blake <eblake@redhat.com>
To: "Marc-André Lureau" <marcandre.lureau@redhat.com>, qemu-devel@nongnu.org
Cc: berrange@redhat.com, armbru@redhat.com, pbonzini@redhat.com
Subject: Re: [Qemu-devel] [PATCH v3 3/4] qobject: replace qobject_incref/QINCREF qobject_decref/QDECREF
Date: Thu, 29 Mar 2018 11:23:26 -0500 [thread overview]
Message-ID: <b041bde4-b926-2ede-d8a5-4721dafe6736@redhat.com> (raw)
In-Reply-To: <20180329154833.566-4-marcandre.lureau@redhat.com>
On 03/29/2018 10:48 AM, Marc-André Lureau wrote:
> Now that we can safely call QOBJECT() on QObject * and children types,
> we can have a single macro to ref/unref the object.
>
> Change the incref/decref prefix name for the more common ref/unref.
>
> Note that before the patch, "QDECREF(obj)" was problematic because it
> would expand to "obj ? obj : ...", which could evaluate "obj" multiple
> times.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> +++ b/include/qapi/qmp/qobject.h
> @@ -48,14 +48,6 @@ struct QObject {
> __x ? container_of(&(__x)->base, QObject, base) : NULL; \
> })
>
> -/* High-level interface for qobject_incref() */
> -#define QINCREF(obj) \
> - qobject_incref(QOBJECT(obj))
> -
> -/* High-level interface for qobject_decref() */
> -#define QDECREF(obj) \
> - qobject_decref(obj ? QOBJECT(obj) : NULL)
> -
Interesting choice to move the macros...
> /* Required for qobject_to() */
> #define QTYPE_CAST_TO_QNull QTYPE_QNULL
> #define QTYPE_CAST_TO_QNum QTYPE_QNUM
> @@ -78,10 +70,7 @@ static inline void qobject_init(QObject *obj, QType type)
> obj->base.type = type;
> }
>
> -/**
> - * qobject_incref(): Increment QObject's reference count
> - */
> -static inline void qobject_incref(QObject *obj)
> +static inline void qobject_ref(QObject *obj)
> {
> if (obj) {
> obj->base.refcnt++;
> @@ -102,11 +91,7 @@ bool qobject_is_equal(const QObject *x, const QObject *y);
> */
> void qobject_destroy(QObject *obj);
>
> -/**
> - * qobject_decref(): Decrement QObject's reference count, deallocate
> - * when it reaches zero
> - */
> -static inline void qobject_decref(QObject *obj)
> +static inline void qobject_unref(QObject *obj)
> {
> assert(!obj || obj->base.refcnt);
> if (obj && --obj->base.refcnt == 0) {
> @@ -114,6 +99,19 @@ static inline void qobject_decref(QObject *obj)
> }
> }
>
> +/**
> + * qobject_ref(): Increment QObject's reference count
> + */
> +#define qobject_ref(obj) \
> + qobject_ref(QOBJECT(obj))
...below the functions of the same name. C preprocessor rules guarantee
that you don't get infinite expansion, although I did a double-take the
first time I read through the patch (especially since your v2 used the
name qobject_ref_impl() for the function, distinct from the macro name).
Worth a comment?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2018-03-29 16:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-29 15:48 [Qemu-devel] [PATCH v3 0/4] RFC: simplify qobject refcount Marc-André Lureau
2018-03-29 15:48 ` [Qemu-devel] [PATCH v3 1/4] qobject: ensure base is at offset 0 Marc-André Lureau
2018-03-29 15:48 ` [Qemu-devel] [PATCH v3 2/4] qobject: introduce QObjectCommon Marc-André Lureau
2018-03-29 16:15 ` Eric Blake
2018-03-29 15:48 ` [Qemu-devel] [PATCH v3 3/4] qobject: replace qobject_incref/QINCREF qobject_decref/QDECREF Marc-André Lureau
2018-03-29 16:23 ` Eric Blake [this message]
2018-04-13 16:13 ` Paolo Bonzini
2018-03-29 15:48 ` [Qemu-devel] [PATCH v3 4/4] qobject: modify qobject_ref() to assert on NULL and return obj Marc-André Lureau
2018-03-29 16:10 ` Eric Blake
2018-04-13 16:05 ` Marc-André Lureau
2018-03-31 6:26 ` [Qemu-devel] [PATCH v3 0/4] RFC: simplify qobject refcount no-reply
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