linux-kernel - Re: [PATCH v2] printf: convert test

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Message-ID: <CAJ-ks9kOpAVq=-b2AXp02F2gJEAmJZxKE=UAGa5ypsVE_an3pQ@mail.gmail.com>
Date: Tue, 20 Jan 2026 10:50:09 -0500
From: Tamir Duberstein <tamird@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>, 
	linux-kernel@...r.kernel.org, oe-kbuild-all@...ts.linux.dev, 
	llvm@...ts.linux.dev, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] printf: convert test_hashed into macro

On Mon, Jan 19, 2026 at 3:21 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Fri, Jan 16, 2026 at 11:27:03AM -0500, Tamir Duberstein wrote:
> > This allows the compiler to check the arguments against the __printf
>
> __printf() since it takes parameters, OTOH it's an attribute at the end,
> so I have no strong opinion on how to spell it.
>
> > attribute on __test. This produces better diagnostics when incorrect
>
> __test()
>
> *This is reference to a function.
>
> > inputs are passed.
>
> ...
>
> > +/*
> > + * This is a macro so that the compiler can compare its arguments to the
> > + * __printf attribute on __test. This cannot be a function with a __printf
> > + * attribute because GCC requires __printf functions to be variadic.
>
> As per commit message remarks.
>
> > + */
> > +#define test_hashed(kunittest, fmt, p)                                   \
> > +     do {                                                             \
> > +             char buf[PLAIN_BUF_SIZE];                                \
> > +             plain_hash_to_buffer(kunittest, p, buf, PLAIN_BUF_SIZE); \
> > +             test(buf, fmt, p);                                       \
> > +     } while (0)
>
> Make sure you used tabs to indent the \:s.
>
> ...
>
> The downside of a macro is a killing of compile-time type checks.

This macro still bottoms out in __test() which is a function, so I
believe it preserves (and enhances, per the commit message)
compile-time checks.

I'll send v3 with the changes you requested above.

>
> --
> With Best Regards,
> Andy Shevchenko
>
>