Re: [Qemu-devel] [PATCH 07/10] qapi: place outermost object on qiv stack

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/22/2012 06:51 AM, Paolo Bonzini wrote:
> This is a slight change in the implementation of QMPInputVisitor
> that helps when adding strict mode.
>
> Const QObjects cannot be inc/decref-ed, and that's why QMPInputVisitor
> relies heavily on weak references to inner objects.  I'm not removing
> the weak references now, but since refcount+const is a lost battle in C
> (C++ has "mutable") I think removing const is fine in this case.
>
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

But I seem to recall that this was this way because some QMP function returns a 
const QObject... oh well, if things still compile with this patch, I'm happy 
with it.

Regards,

Anthony Liguori

> ---
>   qapi/qmp-input-visitor.c |   41 +++++++++++++++++------------------------
>   1 files changed, 17 insertions(+), 24 deletions(-)
>
> diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
> index dfc859a..97a0186 100644
> --- a/qapi/qmp-input-visitor.c
> +++ b/qapi/qmp-input-visitor.c
> @@ -22,14 +22,13 @@
>
>   typedef struct StackObject
>   {
> -    const QObject *obj;
> -    const  QListEntry *entry;
> +    QObject *obj;
> +    const QListEntry *entry;
>   } StackObject;
>
>   struct QmpInputVisitor
>   {
>       Visitor visitor;
> -    QObject *obj;
>       StackObject stack[QIV_STACK_SIZE];
>       int nb_stack;
>   };
> @@ -39,21 +38,15 @@ static QmpInputVisitor *to_qiv(Visitor *v)
>       return container_of(v, QmpInputVisitor, visitor);
>   }
>
> -static const QObject *qmp_input_get_object(QmpInputVisitor *qiv,
> -                                           const char *name)
> +static QObject *qmp_input_get_object(QmpInputVisitor *qiv,
> +                                     const char *name)
>   {
> -    const QObject *qobj;
> -
> -    if (qiv->nb_stack == 0) {
> -        qobj = qiv->obj;
> -    } else {
> -        qobj = qiv->stack[qiv->nb_stack - 1].obj;
> -    }
> +    QObject *qobj = qiv->stack[qiv->nb_stack - 1].obj;
>
>       if (qobj) {
>           if (name&&  qobject_type(qobj) == QTYPE_QDICT) {
>               return qdict_get(qobject_to_qdict(qobj), name);
> -        } else if (qiv->nb_stack>  0&&  qobject_type(qobj) == QTYPE_QLIST) {
> +        } else if (qiv->stack[qiv->nb_stack - 1].entry) {
>               return qlist_entry_obj(qiv->stack[qiv->nb_stack - 1].entry);
>           }
>       }
> @@ -61,7 +54,7 @@ static const QObject *qmp_input_get_object(QmpInputVisitor *qiv,
>       return qobj;
>   }
>
> -static void qmp_input_push(QmpInputVisitor *qiv, const QObject *obj, Error **errp)
> +static void qmp_input_push(QmpInputVisitor *qiv, QObject *obj, Error **errp)
>   {
>       qiv->stack[qiv->nb_stack].obj = obj;
>       qiv->stack[qiv->nb_stack].entry = NULL;
> @@ -83,7 +76,7 @@ static void qmp_input_start_struct(Visitor *v, void **obj, const char *kind,
>                                      const char *name, size_t size, Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>       Error *err = NULL;
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QDICT) {
> @@ -113,7 +106,7 @@ static void qmp_input_end_struct(Visitor *v, Error **errp)
>   static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QLIST) {
>           error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
> @@ -160,7 +153,7 @@ static void qmp_input_type_int(Visitor *v, int64_t *obj, const char *name,
>                                  Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QINT) {
>           error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
> @@ -175,7 +168,7 @@ static void qmp_input_type_bool(Visitor *v, bool *obj, const char *name,
>                                   Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QBOOL) {
>           error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
> @@ -190,7 +183,7 @@ static void qmp_input_type_str(Visitor *v, char **obj, const char *name,
>                                  Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QSTRING) {
>           error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
> @@ -205,7 +198,7 @@ static void qmp_input_type_number(Visitor *v, double *obj, const char *name,
>                                     Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj || qobject_type(qobj) != QTYPE_QFLOAT) {
>           error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
> @@ -220,7 +213,7 @@ static void qmp_input_start_optional(Visitor *v, bool *present,
>                                        const char *name, Error **errp)
>   {
>       QmpInputVisitor *qiv = to_qiv(v);
> -    const QObject *qobj = qmp_input_get_object(qiv, name);
> +    QObject *qobj = qmp_input_get_object(qiv, name);
>
>       if (!qobj) {
>           *present = false;
> @@ -237,7 +230,7 @@ Visitor *qmp_input_get_visitor(QmpInputVisitor *v)
>
>   void qmp_input_visitor_cleanup(QmpInputVisitor *v)
>   {
> -    qobject_decref(v->obj);
> +    qobject_decref(v->stack[0].obj);
>       g_free(v);
>   }
>
> @@ -259,8 +252,8 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
>       v->visitor.type_number = qmp_input_type_number;
>       v->visitor.start_optional = qmp_input_start_optional;
>
> -    v->obj = obj;
> -    qobject_incref(v->obj);
> +    qmp_input_push(v, obj, NULL);
> +    qobject_incref(obj);
>
>       return v;
>   }