linux-kernel - Re: [PATCH] kunit: Fix a NULL vs IS

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Message-ID: <CABVgOSmxsfxZ9tPpnJZF+3FUymw0Lv=zsBx5UGYD+83-qnAagw@mail.gmail.com>
Date: Fri, 12 Jan 2024 07:39:14 +0800
From: David Gow <davidgow@...gle.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Brendan Higgins <brendan.higgins@...ux.dev>, linux-kselftest@...r.kernel.org, 
	kunit-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] kunit: Fix a NULL vs IS_ERR() bug

On Thu, 11 Jan 2024 at 02:55, Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> The kunit_device_register() function doesn't return NULL, it returns
> error pointers.  Change the KUNIT_ASSERT_NOT_NULL() to check for
> ERR_OR_NULL().
>
> Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---

Nice catch, thanks!

Reviewed-by: David Gow <davidgow@...gle.com>

> It's a pity that there isn't a KUNIT_ASSERT_NOT_ERR_PTR() macro...

I think we'll add one, but I'm not yet totally convinced that it would
be better than using ASSERT_NOT_ERR_OR_NULL() in cases like this,
where we're:
1. In a test; and,
2. using the pointer afterwards, expecting it to be valid
(dereferencing it and/or passing it to functions which will)

This is largely because it'd be nicer, if the pointer is NULL (due to
a bug), to get a more explicit assertion failure, rather than a crash.
It does make the test code less indicative of how the APIs are meant
to be used elsewhere, though, and annoys the static analysis, though.

Thoughts?

-- David

>  lib/kunit/kunit-test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
> index c4259d910356..f7980ef236a3 100644
> --- a/lib/kunit/kunit-test.c
> +++ b/lib/kunit/kunit-test.c
> @@ -720,7 +720,7 @@ static void kunit_device_cleanup_test(struct kunit *test)
>         long action_was_run = 0;
>
>         test_device = kunit_device_register(test, "my_device");
> -       KUNIT_ASSERT_NOT_NULL(test, test_device);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_device);
>
>         /* Add an action to verify cleanup. */
>         devm_add_action(test_device, test_dev_action, &action_was_run);
> --
> 2.43.0
>

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