Re: [PATCH] bug: shut up format attribute warning for clang as well

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Mar 20, 2026 at 10:14:25PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Like gcc, clang-22 now also warns about a function that it
> incorrectly identifies as a printf-style format:
> 
> lib/bug.c:190:22: error: diagnostic behavior may be improved by adding the 'format(printf, 1, 0)' attribute to the declaration of '__warn_printf' [-Werror,-Wmissing-format-attribute]
>   179 | static void __warn_printf(const char *fmt, struct pt_regs *regs)
>       | __attribute__((format(printf, 1, 0)))
>   180 | {
>   181 |         if (!fmt)
>   182 |                 return;
>   183 |
>   184 | #ifdef HAVE_ARCH_BUG_FORMAT_ARGS
>   185 |         if (regs) {
>   186 |                 struct arch_va_list _args;
>   187 |                 va_list *args = __warn_args(&_args, regs);
>   188 |
>   189 |                 if (args) {
>   190 |                         vprintk(fmt, *args);
>       |                                           ^
> 
> Turn off this warning for all compilers and versions.
> 
> Fixes: d36067d6ea00 ("bug: Hush suggest-attribute=format for __warn_printf()")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Yeah, it looks like this flag has been recognized by clang for a long
time for GCC compatibility but it only recently started matching GCC's
behavior.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  lib/bug.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/lib/bug.c b/lib/bug.c
> index bbc301097749..374feb144f0b 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -174,8 +174,7 @@ struct bug_entry *find_bug(unsigned long bugaddr)
>  }
>  
>  __diag_push();
> -__diag_ignore(GCC, all, "-Wsuggest-attribute=format",
> -	      "Not a valid __printf() conversion candidate.");
> +__diag_ignore_all("-Wmissing-format-attribute", "Not a valid __printf() conversion candidate.");
>  static void __warn_printf(const char *fmt, struct pt_regs *regs)
>  {
>  	if (!fmt)
> -- 
> 2.39.5
>