linux-kernel - Re: [PATCH v3 1/1] x86, relocs: add printf attribute to die()

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Message-ID: <20170201090455.GA23627@gmail.com>
Date:   Wed, 1 Feb 2017 10:04:55 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Nicolas Iooss <nicolas.iooss_linux@....org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] x86, relocs: add printf attribute to die()


* Nicolas Iooss <nicolas.iooss_linux@....org> wrote:

> Adding such an attribute helps to detect errors in the format string at
> build time. After doing this, the compiler complains about such issues:
> 
>     arch/x86/tools/relocs.c:460:5: error: format specifies type 'int'
>     but the argument has type 'Elf64_Xword' (aka 'unsigned long')
>     [-Werror,-Wformat]
>                                     sec->shdr.sh_size);
>                                     ^~~~~~~~~~~~~~~~~
>     arch/x86/tools/relocs.c:464:5: error: format specifies type 'int'
>     but the argument has type 'Elf64_Off' (aka 'unsigned long')
>     [-Werror,-Wformat]
>                                     sec->shdr.sh_offset, strerror(errno));
>                                     ^~~~~~~~~~~~~~~~~~~
> 
> When relocs.c is included by relocs_32.c, sec->shdr.sh_size and
> sec->shdr.sh_offset are 32-bit unsigned integers. When the file is
> included by relocs_64.c, these expressions are 64-bit unsigned integers.
> 
> Introduce a PRIuELF macro to define the right format to use when
> printing sh_size and sh_offset values.
> 
> While at it, constify the format attribute of die().
> 
> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
> ---
> I sent the first versions of this patch in September (cf.
> https://patchwork.kernel.org/patch/9312665/) but it has not been
> applied.
> 
> As commit adee8705d251 ("x86/build: Annotate die() with noreturn to fix
> build warning on clang") introduced the noreturn attribute to die(),
> this patch now only adds the printf attribute.
> 
>  arch/x86/tools/relocs.c        | 14 +++++++-------
>  arch/x86/tools/relocs.h        |  3 ++-
>  arch/x86/tools/relocs_32.c     |  3 +++
>  arch/x86/tools/relocs_64.c     |  3 +++
>  arch/x86/tools/relocs_common.c |  2 +-
>  5 files changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
> index 0c2fae8d929d..4cad603b8d58 100644
> --- a/arch/x86/tools/relocs.c
> +++ b/arch/x86/tools/relocs.c
> @@ -397,7 +397,7 @@ static void read_shdrs(FILE *fp)
>  		    ehdr.e_shnum);
>  	}
>  	if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
> -		die("Seek to %d failed: %s\n",
> +		die("Seek to %"PRIuELF" failed: %s\n",

Doesn't a simple "%Ld" work as well?

Thanks,

	Ingo