Re: [PATCH 3/3] printk: Use %zu to format size_t

[John Ogness <john.ogness@linutronix.de>]

On 2021-03-17, Geert Uytterhoeven <geert+renesas@glider.be> wrote:
> When compiling for 32-bit:
>
>     util_lib/elf_info.c: In function ‘dump_dmesg_lockless’:
>     util_lib/elf_info.c:1095:39: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘size_t’ {aka ‘unsigned int’} [-Wformat=]
>      1095 |   fprintf(stderr, "Failed to malloc %lu bytes for prb: %s\n",
> 	  |                                     ~~^
> 	  |                                       |
> 	  |                                       long unsigned int
> 	  |                                     %u
>      1096 |    printk_ringbuffer_sz, strerror(errno));
> 	  |    ~~~~~~~~~~~~~~~~~~~~
> 	  |    |
> 	  |    size_t {aka unsigned int}
>     util_lib/elf_info.c:1101:49: warning: format ‘%lu’ expects
> argument of type ‘long unsigned int’, but argument 3 has type ‘size_t’
> {aka ‘unsigned int’} [-Wformat=]
>      1101 |   fprintf(stderr, "Failed to read prb of size %lu bytes: %s\n",
> 	  |                                               ~~^
> 	  |                                                 |
> 	  |                                                 long unsigned int
> 	  |                                               %u
>      1102 |    printk_ringbuffer_sz, strerror(errno));
> 	  |    ~~~~~~~~~~~~~~~~~~~~
> 	  |    |
> 	  |    size_t {aka unsigned int}
>
> Indeed, "size_t" is "unsigned int" on 32-bit platforms, and "unsigned
> long" on 64-bit platforms.
>
> Fix this by formatting using "%zu".
>
> Fixes: 4149df9005f2cdd2 ("printk: add support for lockless ringbuffer")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: John Ogness <john.ogness@linutronix.de>

> ---
>  util_lib/elf_info.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
> index 7c0a2c345379a7ca..676926ca8c5f3766 100644
> --- a/util_lib/elf_info.c
> +++ b/util_lib/elf_info.c
> @@ -1092,13 +1092,13 @@ static void dump_dmesg_lockless(int fd, void (*handler)(char*, unsigned int))
>  	kaddr = read_file_pointer(fd, vaddr_to_offset(prb_vaddr));
>  	m.prb = calloc(1, printk_ringbuffer_sz);
>  	if (!m.prb) {
> -		fprintf(stderr, "Failed to malloc %lu bytes for prb: %s\n",
> +		fprintf(stderr, "Failed to malloc %zu bytes for prb: %s\n",
>  			printk_ringbuffer_sz, strerror(errno));
>  		exit(64);
>  	}
>  	ret = pread(fd, m.prb, printk_ringbuffer_sz, vaddr_to_offset(kaddr));
>  	if (ret != printk_ringbuffer_sz) {
> -		fprintf(stderr, "Failed to read prb of size %lu bytes: %s\n",
> +		fprintf(stderr, "Failed to read prb of size %zu bytes: %s\n",
>  			printk_ringbuffer_sz, strerror(errno));
>  		exit(65);
>  	}

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