linux-kernel - Re: [PATCH v4] lib/test_printf.c: fix clang -Wformat warnings

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Date:   Thu, 28 Jul 2022 12:05:18 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Justin Stitt <justinstitt@...gle.com>, ndesaulniers@...gle.com,
        andriy.shevchenko@...ux.intel.com, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, rostedt@...dmis.org,
        senozhatsky@...omium.org, trix@...hat.com
Subject: Re: [PATCH v4] lib/test_printf.c: fix clang -Wformat warnings

On Wed 2022-07-27 12:39:32, Nathan Chancellor wrote:
> Hi Petr,
> 
> On Tue, Jul 19, 2022 at 02:17:47PM +0200, Petr Mladek wrote:
> > On Mon 2022-07-18 16:06:26, Justin Stitt wrote:
> > > see warnings:
> > > | lib/test_printf.c:157:52: error: format specifies type 'unsigned char'
> > > | but the argument has type 'int' [-Werror,-Wformat]
> > > test("0|1|1|128|255",
> > > | "%hhu|%hhu|%hhu|%hhu|%hhu", 0, 1, 257, 128, -1);
> > > -
> > > | lib/test_printf.c:158:55: error: format specifies type 'char' but the
> > > | argument has type 'int' [-Werror,-Wformat] test("0|1|1|-128|-1",
> > > | "%hhd|%hhd|%hhd|%hhd|%hhd", 0, 1, 257, 128, -1);
> > > -
> > > | lib/test_printf.c:159:41: error: format specifies type 'unsigned
> > > short'
> > > | but the argument has type 'int' [-Werror,-Wformat]
> > > | test("2015122420151225", "%ho%ho%#ho", 1037, 5282, -11627);
> > > 
> > > There's an ongoing movement to eventually enable the -Wformat flag for
> > > clang. Previous patches have targeted incorrect usage of
> > > format specifiers. In this case, however, the "incorrect" format
> > > specifiers are intrinsically part of the test cases. Hence, fixing them
> > > would be misaligned with their intended purpose. My proposed fix is to
> > > simply disable the warnings so that one day a clean build of the kernel
> > > with clang (and -Wformat enabled) would be possible. It would also keep
> > > us in the green for alot of the CI bots.
> > > 
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/378
> > > Suggested-by: Nathan Chancellor <nathan@...nel.org>
> > > Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> > 
> > Looks good to me:
> > 
> > Reviewed-by: Petr Mladek <pmladek@...e.com>
> 
> Would you be able to take this for 5.20 or should we ask Andrew to pick
> it up? It seems you two seem to split applying patches to this file and
> we are trying to get -Wformat enabled for clang in 5.20.

I take most vsprintf-related patches via the printk git tree
last few years.

Anyway, I have just committed the patch into printk/linux.git,
branch for-5.20.

Best Regards,
Petr