Re: [Linux-kernel-mentees] [PATCH] kunit: fix: kunit_binary_assert_format() only prints signed int

[Brendan Higgins via Linux-kernel-mentees <linux-kernel-mentees@lists.linuxfoundation.org>]

On Wed, Aug 19, 2020 at 12:46 PM Vitor Massaru Iha <vitor@massaru.org> wrote:
>
> Some tests, such as overflow_kunit(), uses unsigned int,
> But kunit_binary_assert_format() only prints signed int,
> this commit also deals with the unsigned int print.
>
> Signed-off-by: Vitor Massaru Iha <vitor@massaru.org>
> ---
>  lib/kunit/assert.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/lib/kunit/assert.c b/lib/kunit/assert.c
> index 202f9fdeed0e..3ae90c09986a 100644
> --- a/lib/kunit/assert.c
> +++ b/lib/kunit/assert.c
> @@ -104,12 +104,23 @@ void kunit_binary_assert_format(const struct kunit_assert *assert,
>                                   binary_assert->left_text,
>                                   binary_assert->operation,
>                                   binary_assert->right_text);
> -               string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld\n",
> +
> +               if (binary_assert->left_value - 1 < 0) {
> +                       string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld\n",
> +                                 binary_assert->left_text,
> +                                 binary_assert->left_value);
> +                       string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld",
> +                                 binary_assert->right_text,
> +                                 binary_assert->right_value);
> +               }
> +               else {
> +                       string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %llu\n",
>                                   binary_assert->left_text,
>                                   binary_assert->left_value);
> -               string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld",
> +                       string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %llu",
>                                   binary_assert->right_text,
>                                   binary_assert->right_value);
> +               }

I agree that you found a bug here; however, I disagree that this is
the correct fix. Given that the value is stored as a long long; isn't
the value always stored as a signed value? So if the value overflows,
won't it still not pass the check you have here?

>         }
>         kunit_assert_print_msg(assert, stream);
>  }
>
> base-commit: d43c7fb05765152d4d4a39a8ef957c4ea14d8847
> prerequisite-patch-id: bf4b0962b0b955e4e45f5d25fece889562118158
> --
> 2.26.2
>
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