Re: [Qemu-devel] [PATCH v2 23/26] qapi: Make input visitors detect unvisited list tails

[Eric Blake <eblake@redhat.com>]

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On 02/26/2017 03:43 PM, Markus Armbruster wrote:
> Fix the design flaw demonstrated in the previous commit: new method
> check_list() lets input visitors report that unvisited input remains
> for a list, exactly like check_struct() lets them report that
> unvisited input remains for a struct or union.
> 
> Implement the method for the qobject input visitor (straightforward),
> and the string input visitor (less so, due to the magic list syntax
> there).  The opts visitor's list magic is even more impenetrable, and
> all I can do there today is a stub with a FIXME comment.  No worse
> than before.

Yeah, I know what you mean (having worked on all three visitors in prior
patches).  The opts visitor is just painful.

> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---

> 
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 2de6377..fe7b988 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -326,6 +326,11 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
>                      return;
>                  }
>              }
> +            visit_check_list(v, &err);
> +            if (err) {
> +                error_propagate(errp, err);
> +                return;
> +            }
>              visit_end_list(v, NULL);

This doesn't look right.  You want the visit_end_list() call to occur
unconditionally, even when visit_check_list() fails, so as to free any
resources allocated by the visitor.


> +++ b/tests/test-string-input-visitor.c
> @@ -160,17 +160,9 @@ static void test_visitor_in_intList(TestInputVisitorData *data,
>      /* Would be simpler if the visitor genuinely supported virtual walks */
>      visit_start_list(v, NULL, (GenericList **)&res, sizeof(*res),
>                       &error_abort);
> -    tail = res;
> -    visit_type_int64(v, NULL, &tail->value, &error_abort);
> -    g_assert_cmpint(tail->value, ==, 0);
> -    tail = (int64List *)visit_next_list(v, (GenericList *)tail, sizeof(*res));
> -    g_assert(tail);
> -    visit_type_int64(v, NULL, &tail->value, &error_abort);
> -    g_assert_cmpint(tail->value, ==, 2);
> -    tail = (int64List *)visit_next_list(v, (GenericList *)tail, sizeof(*res));
> -    g_assert(tail);
> +    visit_check_list(v, &err);

You are still calling visit_check_list() after a partial visit, but why
change from a 2/3 visit to a 0/3 visit?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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