linux-kernel - Re: [PATCH] selftests: capabilities: convert error output to TAP13 ksft framework

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Date:   Thu, 27 Jul 2017 19:13:15 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Shuah Khan <shuah@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Shuah Khan <shuahkh@....samsung.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests: capabilities: convert error output to TAP13
 ksft framework

On Thu, Jul 27, 2017 at 1:32 PM, Shuah Khan <shuah@...nel.org> wrote:
> On 07/27/2017 12:50 PM, Andy Lutomirski wrote:
>> On Wed, Jul 26, 2017 at 2:18 PM, Shuah Khan <shuahkh@....samsung.com> wrote:
>>> Convert errx() and err() usage to appropriate TAP13 ksft API.
>>>
>>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
>>> ---
>>>  tools/testing/selftests/capabilities/test_execve.c | 105 ++++++++++++---------
>>>  .../testing/selftests/capabilities/validate_cap.c  |   9 +-
>>>  2 files changed, 65 insertions(+), 49 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
>>> index 7c38233292b0..cf6778441381 100644
>>> --- a/tools/testing/selftests/capabilities/test_execve.c
>>> +++ b/tools/testing/selftests/capabilities/test_execve.c
>>> @@ -1,7 +1,6 @@
>>>  #define _GNU_SOURCE
>>>
>>>  #include <cap-ng.h>
>>> -#include <err.h>
>>>  #include <linux/capability.h>
>>>  #include <stdbool.h>
>>>  #include <string.h>
>>> @@ -39,29 +38,32 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
>>>         int buf_len;
>>>
>>>         buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
>>> -       if (buf_len < 0) {
>>> -               err(1, "vsnprintf failed");
>>> -       }
>>> -       if (buf_len >= sizeof(buf)) {
>>> -               errx(1, "vsnprintf output truncated");
>>> -       }
>>> +       if (buf_len < 0)
>>> +               ksft_exit_fail_msg("vsnprintf failed - %s\n", strerror(errno));
>>
>> Could this not be a hypothetical ksft_exit_fail_msg_err or similar?
>> Or a shorter name like ksft_fatal_err()?
>>
>>
>
> Is there a reason to add _err() suffix?
>
> ksft_exit_fail_msg() is a generic routine for a test to exit
> with a test failure and print a message. The message doesn't
> necessarily need to be a standard error message such as the
> one err() or errx() or strerror() generate.
>
> In some cases test could fail with a standard error condition,
> but not always. In that context, it doesn't make sense to add
> _err suffix. I leveraged this generic function to replace err()
> and errx() usages adding strerror() not loose the important
> information.

The idea behind the _err version is to avoid the extra typing to
report errno.  I suppose you could always report errno, but there are
contexts where errno is meaningless or garbage.