Re: [Qemu-devel] [PATCH] util: add is_equal to UUID API

[Daniel P. Berrange]

On Fri, Nov 24, 2017 at 06:34:03PM +0100, Thomas Huth wrote:
> On 24.11.2017 15:32, Roman Kagan wrote:
> > It's going to be useful, in particular, in VMBus code massively using
> > uuids aka GUIDs.
> > 
> > Signed-off-by: Roman Kagan <address@hidden>
> > ---
> >  include/qemu/uuid.h |  2 ++
> >  tests/test-uuid.c   | 24 ++++++++++++++++++++++++
> >  util/uuid.c         |  7 ++++++-
> >  3 files changed, 32 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/qemu/uuid.h b/include/qemu/uuid.h
> > index afe4840296..09489ce5c5 100644
> > --- a/include/qemu/uuid.h
> > +++ b/include/qemu/uuid.h
> > @@ -48,6 +48,8 @@ void qemu_uuid_generate(QemuUUID *out);
> >  
> >  int qemu_uuid_is_null(const QemuUUID *uu);
> >  
> > +int qemu_uuid_is_equal(const QemuUUID *lhv, const QemuUUID *rhv);
> > +
> >  void qemu_uuid_unparse(const QemuUUID *uuid, char *out);
> >  
> >  char *qemu_uuid_unparse_strdup(const QemuUUID *uuid);
> > diff --git a/tests/test-uuid.c b/tests/test-uuid.c
> > index d3a2791fd4..c6c8148117 100644
> > --- a/tests/test-uuid.c
> > +++ b/tests/test-uuid.c
> > @@ -116,6 +116,29 @@ static void test_uuid_is_null(void)
> >      g_assert_false(qemu_uuid_is_null(&uuid_not_null_2));
> >  }
> >  
> > +static void test_uuid_is_equal(void)
> > +{
> > +    int i;
> > +    QemuUUID uuid;
> > +    QemuUUID uuid_null = { };
> > +    QemuUUID uuid_not_null = { { {
> > +        0x58, 0x6e, 0xce, 0x27, 0x7f, 0x09, 0x41, 0xe0,
> > +        0x9e, 0x74, 0xe9, 0x01, 0x31, 0x7e, 0x9d, 0x42
> > +    } } };
> > +    QemuUUID uuid_null_2 = uuid_null;
> > +    QemuUUID uuid_not_null_2 = uuid_not_null;
> > +
> > +    g_assert(qemu_uuid_is_equal(&uuid_null, &uuid_null_2));
> > +    g_assert(qemu_uuid_is_equal(&uuid_not_null, &uuid_not_null_2));
> > +    g_assert_false(qemu_uuid_is_equal(&uuid_null, &uuid_not_null));
> > +
> > +    for (i = 0; i < 100; ++i) {
> > +        qemu_uuid_generate(&uuid);
> > +        g_assert_false(qemu_uuid_is_equal(&uuid_null, &uuid));
> > +        g_assert_false(qemu_uuid_is_equal(&uuid_not_null, &uuid));
> 
> Isn't there a very low chance that the last line triggers by accident?
> Or uuid_no_null guaranteed to not match the generated one? In the latter
> case, a comment with a short explanation might be helpful here...

Regardless of that question, I think this is rather overkill when we are
just validating the memcmp() works correct in qemu_uuid_is_equal. The
for() loop  here is not really adding any value over what the earlier
asserts already did. In fact the for() loop is arguably testing the
qemu_uuid_generate method, so better done in a separate unit test.

IOW, I would just suggest deleting this for() loop as its adding no
value.


Regards,
Daniel
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