Re: [PATCH 1/2] btrfs-progs: utils: Replace __attribute__(fallthrough)

[Nikolay Borisov <nborisov@suse.com>]

On 22.10.19 г. 5:02 ч., Marcos Paulo de Souza wrote:
> From: Marcos Paulo de Souza <mpdesouza@suse.com>
> 
> When compiling with clang, this warning is shown:
> 
> common/utils.c:404:3: warning: declaration does not declare anything [-Wmissing-declarations]
>                 __attribute__ ((fallthrough));
> 
> This attribute seems to silence the same warning in GCC. Changing this
> attribute with /* fallthrough */ fixes the warning for both gcc and
> clang.
> 
> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>

Which clang version are you using? According to
https://clang.llvm.org/docs/AttributeReference.html#fallthrough this
attribute is supported even with the GNU syntax.

> ---
>  common/utils.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/common/utils.c b/common/utils.c
> index 2cf15c33..a88336b3 100644
> --- a/common/utils.c
> +++ b/common/utils.c
> @@ -401,15 +401,15 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_size, unsigned unit_mod
>  	case UNITS_TBYTES:
>  		base *= mult;
>  		num_divs++;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case UNITS_GBYTES:
>  		base *= mult;
>  		num_divs++;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case UNITS_MBYTES:
>  		base *= mult;
>  		num_divs++;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case UNITS_KBYTES:
>  		num_divs++;
>  		break;
> @@ -1135,14 +1135,14 @@ int test_num_disk_vs_raid(u64 metadata_profile, u64 data_profile,
>  	default:
>  	case 4:
>  		allowed |= BTRFS_BLOCK_GROUP_RAID10;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case 3:
>  		allowed |= BTRFS_BLOCK_GROUP_RAID6;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case 2:
>  		allowed |= BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
>  			BTRFS_BLOCK_GROUP_RAID5;
> -		__attribute__ ((fallthrough));
> +		/* fallthrough */
>  	case 1:
>  		allowed |= BTRFS_BLOCK_GROUP_DUP;
>  	}
>