[Qemu-devel] [PATCH] tests/check-qdict: Fix missing brackets

[Qemu-devel] [PATCH] tests/check-qdict: Fix missing brackets

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
boolean; it's got a point.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 tests/check-qdict.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/check-qdict.c b/tests/check-qdict.c
index 81162ee572..6f3fbcf9c1 100644
--- a/tests/check-qdict.c
+++ b/tests/check-qdict.c
@@ -559,7 +559,7 @@ static void qdict_join_test(void)
         g_assert(qdict_size(dict1) == 2);
         g_assert(qdict_size(dict2) == !overwrite);
 
-        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
+        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
         g_assert(qdict_get_int(dict1, "bar") == 23);
 
         if (!overwrite) {
-- 
2.12.2

Re: [Qemu-devel] [PATCH] tests/check-qdict: Fix missing brackets

[Eric Blake]

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On 04/06/2017 10:41 AM, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
> boolean; it's got a point.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  tests/check-qdict.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tests/check-qdict.c b/tests/check-qdict.c
> index 81162ee572..6f3fbcf9c1 100644
> --- a/tests/check-qdict.c
> +++ b/tests/check-qdict.c
> @@ -559,7 +559,7 @@ static void qdict_join_test(void)
>          g_assert(qdict_size(dict1) == 2);
>          g_assert(qdict_size(dict2) == !overwrite);
>  
> -        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
> +        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));

How is the test passing pre-patch, and why does it not change the test
post-patch?  Does that mean that overwrite is not doing what we expected?

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


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Re: [Qemu-devel] [PATCH] tests/check-qdict: Fix missing brackets

[Dr. David Alan Gilbert]

* Eric Blake (eblake@redhat.com) wrote:
> On 04/06/2017 10:41 AM, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
> > boolean; it's got a point.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  tests/check-qdict.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tests/check-qdict.c b/tests/check-qdict.c
> > index 81162ee572..6f3fbcf9c1 100644
> > --- a/tests/check-qdict.c
> > +++ b/tests/check-qdict.c
> > @@ -559,7 +559,7 @@ static void qdict_join_test(void)
> >          g_assert(qdict_size(dict1) == 2);
> >          g_assert(qdict_size(dict2) == !overwrite);
> >  
> > -        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
> > +        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
> 
> How is the test passing pre-patch, and why does it not change the test
> post-patch?  Does that mean that overwrite is not doing what we expected?

Pre-patch it passes because either 84 or 42  are valid 'true' values into g_assert.
Post patch it ends up as either:
    qdict_get_int(dict1, "foo") == 42
or
    qdict_get_int(dict1, "foo") == 84

which is what's intended.

Dave

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



--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH for-2.9?] tests/check-qdict: Fix missing brackets

[Eric Blake]

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On 04/06/2017 10:49 AM, Eric Blake wrote:
> On 04/06/2017 10:41 AM, Dr. David Alan Gilbert (git) wrote:
>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>>
>> Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
>> boolean; it's got a point.
>>
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> ---
>>  tests/check-qdict.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tests/check-qdict.c b/tests/check-qdict.c
>> index 81162ee572..6f3fbcf9c1 100644
>> --- a/tests/check-qdict.c
>> +++ b/tests/check-qdict.c
>> @@ -559,7 +559,7 @@ static void qdict_join_test(void)
>>          g_assert(qdict_size(dict1) == 2);
>>          g_assert(qdict_size(dict2) == !overwrite);
>>  
>> -        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
>> +        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
> 
> How is the test passing pre-patch, and why does it not change the test
> post-patch?  Does that mean that overwrite is not doing what we expected?

Replying to myself:

Pre-patch, it was reached twice (once for overwrite=false, once for
overwrite=true), as:

(42 == false) ? 84 : 42
(84 == true) ? 84 : 42

which simplifies to 42 on both iterations, and g_assert(42) succeeds.
In fact, this is a tautology - no matter WHAT value we encounter, the
assert succeeds, so we are not actually testing that the value matters.

Post-patch, it becomes:

42 == (false ? 84 : 42)
84 == (true ? 84 : 42)

which is then asserting that we actually have the value we expect.

Reviewed-by: Eric Blake <eblake@redhat.com>

Safe for 2.9, but late enough that it also doesn't matter if it slips
until 2.10.

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


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Re: [Qemu-devel] [PATCH for-2.9?] tests/check-qdict: Fix missing brackets

[Philippe Mathieu-Daudé]

On 04/06/2017 12:55 PM, Eric Blake wrote:
> On 04/06/2017 10:49 AM, Eric Blake wrote:
>> On 04/06/2017 10:41 AM, Dr. David Alan Gilbert (git) wrote:
>>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>>>
>>> Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
>>> boolean; it's got a point.
>>>
>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>> ---
>>>  tests/check-qdict.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/tests/check-qdict.c b/tests/check-qdict.c
>>> index 81162ee572..6f3fbcf9c1 100644
>>> --- a/tests/check-qdict.c
>>> +++ b/tests/check-qdict.c
>>> @@ -559,7 +559,7 @@ static void qdict_join_test(void)
>>>          g_assert(qdict_size(dict1) == 2);
>>>          g_assert(qdict_size(dict2) == !overwrite);
>>>
>>> -        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
>>> +        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
>>
>> How is the test passing pre-patch, and why does it not change the test
>> post-patch?  Does that mean that overwrite is not doing what we expected?
>
> Replying to myself:
>
> Pre-patch, it was reached twice (once for overwrite=false, once for
> overwrite=true), as:
>
> (42 == false) ? 84 : 42
> (84 == true) ? 84 : 42
>
> which simplifies to 42 on both iterations, and g_assert(42) succeeds.
> In fact, this is a tautology - no matter WHAT value we encounter, the
> assert succeeds, so we are not actually testing that the value matters.
>
> Post-patch, it becomes:
>
> 42 == (false ? 84 : 42)
> 84 == (true ? 84 : 42)
>
> which is then asserting that we actually have the value we expect.
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>
> Safe for 2.9, but late enough that it also doesn't matter if it slips
> until 2.10.
>

another case which demonstrate human _optimized_ C is more bug prone 
than verbose basic code...

Most cpp generates the same asm code with the following C:

if (overwrite) {
     g_assert(qdict_get_int(dict1, "foo") == 84);
} else {
     g_assert(qdict_get_int(dict1, "foo") == 42);
}

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Re: [Qemu-devel] [PATCH] tests/check-qdict: Fix missing brackets

[Markus Armbruster]

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> writes:

> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Gcc 7 (on Fedora 26) spotted odd use of integers instead of a
> boolean; it's got a point.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  tests/check-qdict.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tests/check-qdict.c b/tests/check-qdict.c
> index 81162ee572..6f3fbcf9c1 100644
> --- a/tests/check-qdict.c
> +++ b/tests/check-qdict.c
> @@ -559,7 +559,7 @@ static void qdict_join_test(void)
>          g_assert(qdict_size(dict1) == 2);
>          g_assert(qdict_size(dict2) == !overwrite);
>  
> -        g_assert(qdict_get_int(dict1, "foo") == overwrite ? 84 : 42);
> +        g_assert(qdict_get_int(dict1, "foo") == (overwrite ? 84 : 42));
>          g_assert(qdict_get_int(dict1, "bar") == 23);
>  
>          if (!overwrite) {

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

Applied to qapi-next, thanks!