netdev - Re: [PATCH 1/1] tools/lib/libbpf.c: fix string format to allow build on arm32

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Date:   Wed, 23 May 2018 12:41:14 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Sirio Balmelli <sirio@...d.ch>
Cc:     netdev@...r.kernel.org, kafai@...com
Subject: Re: [PATCH 1/1] tools/lib/libbpf.c: fix string format to allow build
 on arm32

[ +Martin ]

On 05/21/2018 08:59 AM, Sirio Balmelli wrote:
> On arm32, 'cd tools/testing/selftests/bpf && make' fails with:
> 
> libbpf.c:80:10: error: format ‘%ld’ expects argument of type ‘long int’, but argument 4 has type ‘int64_t {aka long long int}’ [-Werror=format=]
>    (func)("libbpf: " fmt, ##__VA_ARGS__); \
>           ^
> libbpf.c:83:30: note: in expansion of macro ‘__pr’
>  #define pr_warning(fmt, ...) __pr(__pr_warning, fmt, ##__VA_ARGS__)
>                               ^~~~
> libbpf.c:1072:3: note: in expansion of macro ‘pr_warning’
>    pr_warning("map:%s value_type:%s has BTF type_size:%ld != value_size:%u\n",
> 
> To fix, include 'inttypes.h' and change format directive to 'PRIi64'.
> 
> Signed-off-by: Sirio Balmelli <sirio@...d.ch>

Thanks for the fix! One minor comment below.

> ---
>  tools/lib/bpf/libbpf.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 3dbe217bf23e..e2cc8f10c188 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -48,6 +48,8 @@
>  #include "bpf.h"
>  #include "btf.h"
>  
> +#include <inttypes.h>   /* PRIi64 */
> +
>  #ifndef EM_BPF
>  #define EM_BPF 247
>  #endif
> @@ -1042,7 +1044,7 @@ static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf)
>  	}
>  
>  	if (def->key_size != key_size) {
> -		pr_warning("map:%s key_type:%s has BTF type_size:%ld != key_size:%u\n",
> +		pr_warning("map:%s key_type:%s has BTF type_size:%"PRIi64" != key_size:%u\n",
>  			   map->name, name, key_size, def->key_size);
>  		return -EINVAL;
>  	}
> @@ -1069,7 +1071,7 @@ static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf)
>  	}
>  
>  	if (def->value_size != value_size) {
> -		pr_warning("map:%s value_type:%s has BTF type_size:%ld != value_size:%u\n",
> +		pr_warning("map:%s value_type:%s has BTF type_size:%"PRIi64" != value_size:%u\n",
>  			   map->name, name, value_size, def->value_size);

I don't think we need the PRIi64 in here. Could you just change it to 'type_size:%u'
and then cast the 'key_size' resp. 'value_size' to unsigned int? We know at this
point that the type size value is positive anyway, so we only want to show the size
mismatch so simple cast should suffice. Thanks!

>  		return -EINVAL;
>  	}
>