linux-kernel - Re: [PATCH v4 3/3] printf: implicate test line in failure messages

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Message-ID: <CAJ-ks9kadHvF3gKjZh-_oFdb1x_qOR6i1=Jamuaw9iq129gOnQ@mail.gmail.com>
Date: Wed, 19 Feb 2025 15:58:08 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Arpitha Raghunandan <98.arpi@...il.com>, David Gow <davidgow@...gle.com>, 
	Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>, 
	Geert Uytterhoeven <geert@...ux-m68k.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Naveen N Rao <naveen@...nel.org>, 
	Brendan Higgins <brendan.higgins@...ux.dev>, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-m68k@...ts.linux-m68k.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v4 3/3] printf: implicate test line in failure messages

On Wed, Feb 19, 2025 at 3:41 PM Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
>
> On Fri, 14 Feb 2025 at 22:53, Tamir Duberstein <tamird@...il.com> wrote:
> >
> > This improves the failure output by pointing to the failing line at the
> > top level of the test, e.g.:
> >       # test_number: EXPECTATION FAILED at lib/printf_kunit.c:103
> >   lib/printf_kunit.c:167: vsnprintf(buf, 256, "%#-12x", ...) wrote '0x1234abcd  ', expected '0x1234abce  '
> >       # test_number: EXPECTATION FAILED at lib/printf_kunit.c:142
> >   lib/printf_kunit.c:167: kvasprintf(..., "%#-12x", ...) returned '0x1234abcd  ', expected '0x1234abce  '
> >
>
> Actually, I'm not sure that is an improvement as-is, with the two
> different line numbers being printed. It takes some thought to
> recognize which one is relevant and which one is not.

They're both relevant -- `do_test` does a bunch of checks, so you want
to know which particular check failed, but also which invocation at
the top level resulted in that check failing.

> Can't we have a variant of KUNIT_FAIL that allows one to pass the
> file/line info when the caller has better info than the location of
> the KUNIT_FAIL itself?
>
> >  static void __printf(5, 0)
> > -do_test(struct kunit *kunittest, int bufsize, const char *expect, int elen,
> > -       const char *fmt, va_list ap)
> > +do_test(struct kunit *kunittest, const char *file, const int line, int bufsize, const char *expect,
> > +       int elen, const char *fmt, va_list ap)
>
> This can't be right, the __printf attribute must be updated accordingly.

Good catch. Oddly I'm not able to reproduce any compiler complaints
here, even with the attribute completely removed.