| Message ID | 20180417133602.23832-3-marcandre.lureau@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/17/2018 08:35 AM, Marc-André Lureau wrote: > By moving the base fields to a QObjectBase_, QObject can be a type > which also has a 'base' field. This allows to write a generic either "allows us to write" or "allows writing" > 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 typedef and use a trailing underscore to make it s/not typedef and use/not a typedef and uses/ > obvious it is not for normal use and to avoid potential abuse. > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > --- > +++ b/include/qapi/qmp/qobject.h > @@ -34,13 +34,20 @@ > > #include "qapi/qapi-builtin-types.h" > > -struct QObject { > +/* Not for use outside include/qapi/qmp/ */ > +struct QObjectBase_ { > QType type; > size_t refcnt; > }; > > -/* Get the 'base' part of an object */ > -#define QOBJECT(obj) (&(obj)->base) > +struct QObject { > + struct QObjectBase_ base; I'd add a comment here that this struct must have no other members than base. > +}; > + > +#define QOBJECT(x) ({ \ > + typeof(x) __x = (x); \ > + __x ? container_of(&(__x)->base, QObject, base) : NULL; \ > +}) > With those changes, Reviewed-by: Eric Blake <eblake@redhat.com>
In addition to Eric's comments... Marc-André Lureau <marcandre.lureau@redhat.com> writes: > By moving the base fields to a QObjectBase_, QObject can be a type > which also has a 'base' field. This allows to write 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 typedef and use a trailing underscore to make it > obvious it is not for normal use and to avoid potential abuse. > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> [...] > diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h > index 5206ff9ee1..0a7f800d58 100644 > --- a/include/qapi/qmp/qobject.h > +++ b/include/qapi/qmp/qobject.h > @@ -34,13 +34,20 @@ > > #include "qapi/qapi-builtin-types.h" > > -struct QObject { > +/* Not for use outside include/qapi/qmp/ */ > +struct QObjectBase_ { > QType type; > size_t refcnt; > }; > > -/* Get the 'base' part of an object */ > -#define QOBJECT(obj) (&(obj)->base) > +struct QObject { > + struct QObjectBase_ base; > +}; > + > +#define QOBJECT(x) ({ \ > + typeof(x) __x = (x); \ > + __x ? container_of(&(__x)->base, QObject, base) : NULL; \ > +}) Identifiers that begin with double underscores are reserved for any use. Drop one of the two, please. > > /* High-level interface for qobject_incref() */ > #define QINCREF(obj) \ > @@ -68,8 +75,8 @@ QEMU_BUILD_BUG_MSG(QTYPE__MAX != 7, > static inline void qobject_init(QObject *obj, QType type) > { > assert(QTYPE_NONE < type && type < QTYPE__MAX); > - obj->refcnt = 1; > - obj->type = type; > + obj->base.refcnt = 1; > + obj->base.type = type; > } > > /** [...]
diff --git a/include/qapi/qmp/qbool.h b/include/qapi/qmp/qbool.h index b9a44a1bfe..5f61e38e64 100644 --- a/include/qapi/qmp/qbool.h +++ b/include/qapi/qmp/qbool.h @@ -17,7 +17,7 @@ #include "qapi/qmp/qobject.h" struct QBool { - QObject base; + struct QObjectBase_ base; bool value; }; diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h index 2cc3e906f7..921a28d2d3 100644 --- a/include/qapi/qmp/qdict.h +++ b/include/qapi/qmp/qdict.h @@ -25,7 +25,7 @@ typedef struct QDictEntry { } QDictEntry; struct QDict { - QObject base; + struct QObjectBase_ base; size_t size; QLIST_HEAD(,QDictEntry) table[QDICT_BUCKET_MAX]; }; diff --git a/include/qapi/qmp/qlist.h b/include/qapi/qmp/qlist.h index 5c673acb06..8d2c32ca28 100644 --- a/include/qapi/qmp/qlist.h +++ b/include/qapi/qmp/qlist.h @@ -22,7 +22,7 @@ typedef struct QListEntry { } QListEntry; struct QList { - QObject base; + struct QObjectBase_ base; QTAILQ_HEAD(,QListEntry) head; }; diff --git a/include/qapi/qmp/qnull.h b/include/qapi/qmp/qnull.h index c992ee2ae1..e8ea2c315a 100644 --- a/include/qapi/qmp/qnull.h +++ b/include/qapi/qmp/qnull.h @@ -16,7 +16,7 @@ #include "qapi/qmp/qobject.h" struct QNull { - QObject base; + struct QObjectBase_ base; }; extern QNull qnull_; diff --git a/include/qapi/qmp/qnum.h b/include/qapi/qmp/qnum.h index 3e47475b2c..45bf02a036 100644 --- a/include/qapi/qmp/qnum.h +++ b/include/qapi/qmp/qnum.h @@ -45,7 +45,7 @@ typedef enum { * convert under the hood. */ struct QNum { - QObject base; + struct QObjectBase_ base; QNumKind kind; union { int64_t i64; diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h index 5206ff9ee1..0a7f800d58 100644 --- a/include/qapi/qmp/qobject.h +++ b/include/qapi/qmp/qobject.h @@ -34,13 +34,20 @@ #include "qapi/qapi-builtin-types.h" -struct QObject { +/* Not for use outside include/qapi/qmp/ */ +struct QObjectBase_ { QType type; size_t refcnt; }; -/* Get the 'base' part of an object */ -#define QOBJECT(obj) (&(obj)->base) +struct QObject { + struct QObjectBase_ base; +}; + +#define QOBJECT(x) ({ \ + typeof(x) __x = (x); \ + __x ? container_of(&(__x)->base, QObject, base) : NULL; \ +}) /* High-level interface for qobject_incref() */ #define QINCREF(obj) \ @@ -68,8 +75,8 @@ QEMU_BUILD_BUG_MSG(QTYPE__MAX != 7, static inline void qobject_init(QObject *obj, QType type) { assert(QTYPE_NONE < type && type < QTYPE__MAX); - obj->refcnt = 1; - obj->type = type; + obj->base.refcnt = 1; + obj->base.type = type; } /** @@ -77,8 +84,9 @@ static inline void qobject_init(QObject *obj, QType type) */ static inline void qobject_incref(QObject *obj) { - if (obj) - obj->refcnt++; + if (obj) { + obj->base.refcnt++; + } } /** @@ -101,8 +109,8 @@ void qobject_destroy(QObject *obj); */ static inline void qobject_decref(QObject *obj) { - assert(!obj || obj->refcnt); - if (obj && --obj->refcnt == 0) { + assert(!obj || obj->base.refcnt); + if (obj && --obj->base.refcnt == 0) { qobject_destroy(obj); } } @@ -112,8 +120,8 @@ static inline void qobject_decref(QObject *obj) */ static inline QType qobject_type(const QObject *obj) { - assert(QTYPE_NONE < obj->type && obj->type < QTYPE__MAX); - return obj->type; + assert(QTYPE_NONE < obj->base.type && obj->base.type < QTYPE__MAX); + return obj->base.type; } /** diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h index 30ae260a7f..b3b3d444d2 100644 --- a/include/qapi/qmp/qstring.h +++ b/include/qapi/qmp/qstring.h @@ -16,7 +16,7 @@ #include "qapi/qmp/qobject.h" struct QString { - QObject base; + struct QObjectBase_ base; char *string; size_t length; size_t capacity; diff --git a/qobject/qobject.c b/qobject/qobject.c index 87649c5be5..cf4b7e229e 100644 --- a/qobject/qobject.c +++ b/qobject/qobject.c @@ -37,9 +37,9 @@ static void (*qdestroy[QTYPE__MAX])(QObject *) = { void qobject_destroy(QObject *obj) { - assert(!obj->refcnt); - assert(QTYPE_QNULL < obj->type && obj->type < QTYPE__MAX); - qdestroy[obj->type](obj); + assert(!obj->base.refcnt); + assert(QTYPE_QNULL < obj->base.type && obj->base.type < QTYPE__MAX); + qdestroy[obj->base.type](obj); } @@ -62,11 +62,11 @@ bool qobject_is_equal(const QObject *x, const QObject *y) return true; } - if (!x || !y || x->type != y->type) { + if (!x || !y || x->base.type != y->base.type) { return false; } - assert(QTYPE_NONE < x->type && x->type < QTYPE__MAX); + assert(QTYPE_NONE < x->base.type && x->base.type < QTYPE__MAX); - return qis_equal[x->type](x, y); + return qis_equal[x->base.type](x, y); } diff --git a/tests/check-qdict.c b/tests/check-qdict.c index 2e73c2f86e..029b6b15b9 100644 --- a/tests/check-qdict.c +++ b/tests/check-qdict.c @@ -570,11 +570,11 @@ static void qdict_join_test(void) } /* Check the references */ - g_assert(qdict_get(dict1, "foo")->refcnt == 1); - g_assert(qdict_get(dict1, "bar")->refcnt == 1); + g_assert(qdict_get(dict1, "foo")->base.refcnt == 1); + g_assert(qdict_get(dict1, "bar")->base.refcnt == 1); if (!overwrite) { - g_assert(qdict_get(dict2, "foo")->refcnt == 1); + g_assert(qdict_get(dict2, "foo")->base.refcnt == 1); } /* Clean up */
By moving the base fields to a QObjectBase_, QObject can be a type which also has a 'base' field. This allows to write 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 typedef and use a trailing underscore to make it obvious it is not for normal use and to avoid potential abuse. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> --- include/qapi/qmp/qbool.h | 2 +- include/qapi/qmp/qdict.h | 2 +- include/qapi/qmp/qlist.h | 2 +- include/qapi/qmp/qnull.h | 2 +- include/qapi/qmp/qnum.h | 2 +- include/qapi/qmp/qobject.h | 30 +++++++++++++++++++----------- include/qapi/qmp/qstring.h | 2 +- qobject/qobject.c | 12 ++++++------ tests/check-qdict.c | 6 +++--- 9 files changed, 34 insertions(+), 26 deletions(-)