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From: Markus Armbruster <armbru@redhat.com>
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Date: Wed, 15 Aug 2018 08:24:56 +0200
In-Reply-To: <44875a85-ddcf-6a81-ca42-24fe9b268b93@redhat.com> (Thomas Huth's
	message of "Wed, 15 Aug 2018 08:00:53 +0200")
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Subject: Re: [Qemu-devel] [PATCH 2/6] tests/device-introspection: Check that
 the qom-tree and qtree do not change
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To: Thomas Huth <thuth@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Juan Quintela <quintela@redhat.com>, qemu-devel@nongnu.org, Philippe =?utf-8?Q?Mathie?= =?utf-8?Q?u-Daud=C3=A9?= <f4bug@amsat.org>, Paolo Bonzini <pbonzini@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Thomas Huth <thuth@redhat.com> writes:

> On 08/14/2018 07:53 PM, Markus Armbruster wrote:
>> Thomas Huth <thuth@redhat.com> writes:
> [...]
>>> @@ -115,10 +122,18 @@ static void test_one_device(const char *type)
>>>  
>>>      /*
>>>       * Some devices leave dangling pointers in QOM behind.
>>> -     * "info qom-tree" has a good chance at crashing then
>>> +     * "info qom-tree" or "info qtree" have a good chance at crashing then.
>>> +     * Also make sure that the tree did not change.
>>>       */
>>> -    qom_tree = hmp("info qom-tree");
>>> -    g_free(qom_tree);
>>> +    qom_tree_end = hmp("info qom-tree");
>>> +    g_assert_cmpstr(qom_tree_start, ==, qom_tree_end);
>>> +    g_free(qom_tree_start);
>>> +    g_free(qom_tree_end);
>>> +
>>> +    qtree_end = hmp("info qtree");
>>> +    g_assert_cmpstr(qtree_start, ==, qtree_end);
>>> +    g_free(qtree_start);
>>> +    g_free(qtree_end);
>>>  }
>>>  
>>>  static void test_device_intro_list(void)
>> 
>> Output of "info qom-tree" depends on hash table iteration order, but
>> that could almost be considered a feature here.
>
> Currently, it seems to work fine. If we hit a false positive with
> ordering later, we still can add some code for sorting the output, I guess?

I'm fine with comparing output of info qom-tree and info qtree.

I figure the most likely cause for a change of order would be a series
of QOM tree modifications that cancels out.  There should be *no* QOM
tree modifications.  Thus, "almost a feature".