Re: [PATCH v4 1/1] x86, relocs: add printf attribute to die()

From: Ingo Molnar
Date: Tue Mar 07 2017 - 08:20:14 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 some 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.
>
> Add casts to unsigned long long, which length is always 64-bit, and use
> %llu to format sec->shdr.sh_size and sec->shdr.sh_offset in relocs.c.
>
> While at it, constify the format attribute of die().
>
> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@xxxxxxx>
> ---
> arch/x86/tools/relocs.c | 31 +++++++++++++++++--------------
> arch/x86/tools/relocs.h | 3 ++-
> arch/x86/tools/relocs_common.c | 2 +-
> 3 files changed, 20 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
> index 73eb7fd4aec4..3cc02065c677 100644
> --- a/arch/x86/tools/relocs.c
> +++ b/arch/x86/tools/relocs.c
> @@ -397,8 +397,8 @@ 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",
> - ehdr.e_shoff, strerror(errno));
> + die("Seek to %llu failed: %s\n",
> + (unsigned long long)ehdr.e_shoff, strerror(errno));

Isn't "(u64)" shorter to write?

Thanks,

Ingo