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

From: Ingo Molnar
Date: Wed Feb 01 2017 - 04:05:06 EST



* Nicolas Iooss <nicolas.iooss_linux@xxxxxxx> 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@xxxxxxx>
> ---
> 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