linux-kernel - Re: [PATCH 2/3] kunit: add KUnit array assertions to the example_all_expect_macros

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Date:   Tue, 2 Aug 2022 16:00:31 -0300
From:   Maíra Canal <mairacanal@...eup.net>
To:     Daniel Latypov <dlatypov@...gle.com>,
        André Almeida <andrealmeid@...eup.net>
Cc:     Maíra Canal <mairacanal@...eup.net>,
        melissa.srw@...il.com, daniel@...ll.ch, javierm@...hat.com,
        siqueirajordao@...eup.net, Isabella Basso <isabbasso@...eup.net>,
        jose.exposito89@...il.com, magalilemes00@...il.com,
        tales.aparecida@...il.com, davidgow@...gle.com,
        davem@...emloft.net, Brendan Higgins <brendanhiggins@...gle.com>,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, airlied@...ux.ie, kuba@...nel.org
Subject: Re: [PATCH 2/3] kunit: add KUnit array assertions to the
 example_all_expect_macros_test

On 8/2/22 15:15, 'Daniel Latypov' via KUnit Development wrote:
> On Tue, Aug 2, 2022 at 9:19 AM André Almeida <andrealmeid@...eup.net> wrote:
>> Às 13:12 de 02/08/22, Maíra Canal escreveu:
>>> Increament the example_all_expect_macros_test with the
>>> KUNIT_EXPECT_ARREQ and KUNIT_EXPECT_ARRNEQ macros by creating a test
>>> with array assertions.
>>>
>>> Signed-off-by: Maíra Canal <mairacanal@...eup.net>
>>> ---
>>>  lib/kunit/kunit-example-test.c | 7 +++++++
>>>  1 file changed, 7 insertions(+)
>>>
>>> diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
>>> index f8fe582c9e36..fc81a45d9cbc 100644
>>> --- a/lib/kunit/kunit-example-test.c
>>> +++ b/lib/kunit/kunit-example-test.c
>>> @@ -86,6 +86,9 @@ static void example_mark_skipped_test(struct kunit *test)
>>>   */
>>>  static void example_all_expect_macros_test(struct kunit *test)
>>>  {
>>> +     const u32 array[] = { 0x0F, 0xFF };
>>> +     const u32 expected[] = { 0x1F, 0xFF };
> 
> Given the distance between the definition and their use, perhaps we
> can give them clearer names.
> E.g. array + diff_array, or array1 + array2, etc.
> 
> I think something to indicate they're arrays and that they're different.
> The current name `expected` is a bit unclear.

Thank you for the note, I'll address it at v2.

> 
>>> +
>>>       /* Boolean assertions */
>>>       KUNIT_EXPECT_TRUE(test, true);
>>>       KUNIT_EXPECT_FALSE(test, false);
>>> @@ -109,6 +112,10 @@ static void example_all_expect_macros_test(struct kunit *test)
>>>       KUNIT_EXPECT_STREQ(test, "hi", "hi");
>>>       KUNIT_EXPECT_STRNEQ(test, "hi", "bye");
>>>
>>> +     /* Array assertions */
>>> +     KUNIT_EXPECT_ARREQ(test, expected, expected, 2);
>>> +     KUNIT_EXPECT_ARRNEQ(test, array, expected, 2);
>>
>> ARRAY_SIZE() is usually better than constants is this case.
> 
> Note: that's actually incorrect!
> 

Yep, that's my bad!

> Ah right, this was the other blocker I had in mind.
> I wasn't sure how we'd handle the size parameter.
> 
> Users might think ARRAY_SIZE() is fine and copy-paste it.
> But the size parameter is in units of bytes, not array elements!
> If the element types are not 1 byte, it'll silently not compare the full array.
> 
> We'd want people to use
> KUNIT_EXPECT_ARREQ(test, expected, expected, sizeof(expected));
> 
> But this doesn't work for `u32 *array`, since it'll silently just
> compare 1 byte if people get them mixed up.
> 
> I don't know how we make a maximally fool-proof version of this macro :\

This is a hard one also. I believe that use KUNIT_EXPECT_ARREQ(test,
expected, expected, sizeof(expected)); is more compliant to the
memcpy/memset/memcmp signature. Moreover, this problem also occur for
the KUNIT_EXPECT_EQ(test, memcmp(expected, expected, sizeof(expected)), 0);

I believe that the number of array elements will make it easier for
users to avoid mistakes.

I'll change it internally for size_bytes = (size) * sizeof((left)[0]) on v2.

Best Regards,
- Maíra Canal

>