Re: [Qemu-devel] [PATCH 1/8] qapi: fix NULL pointer dereference

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/16/2011 06:01 AM, Paolo Bonzini wrote:
> QAPI currently cannot deal with no object pushed to the stack,
> and dereferences a NULL pointer.  This is visible with
>
>      qom-get path=/i440fx/piix3 property=romfile
>
> after static non-string properties are introduced.

I'm a bit confused about what's happening here.  What's the significance of 
non-string properties?

Regards,

Anthony Liguori

>
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
> ---
>   qapi/qmp-output-visitor.c |    4 ++--
>   1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
> index f76d015..29575da 100644
> --- a/qapi/qmp-output-visitor.c
> +++ b/qapi/qmp-output-visitor.c
> @@ -65,13 +65,13 @@ static QObject *qmp_output_pop(QmpOutputVisitor *qov)
>   static QObject *qmp_output_first(QmpOutputVisitor *qov)
>   {
>       QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
> -    return e->value;
> +    return e ? e->value : NULL;
>   }
>
>   static QObject *qmp_output_last(QmpOutputVisitor *qov)
>   {
>       QStackEntry *e = QTAILQ_FIRST(&qov->stack);
> -    return e->value;
> +    return e ? e->value : NULL;
>   }
>
>   static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name,