On 2018/11/16 下午4:04, Nikolay Borisov wrote:
> 
> 
> On 16.11.18 г. 9:54 ч., Qu Wenruo wrote:
>> Although most fallthrough case is pretty obvious, we still need to teach
>> the dumb compiler that it's an explicit fallthrough.
>>
>> Also reformat the code to use common indent.
>>
>> Signed-off-by: Qu Wenruo <w...@suse.com>
> 
> Reviewed-by: Nikolay Borisov <nbori...@suse.com>
> 
> Is this attribute dependent on a particular compiler version? Does
> gcc4.4 for example support it?

IIRC unsupported attribute should just be ignored by the compiler, so it
shouldn't cause any problem.

However I'm not 100% perfect sure, as my distribution doesn't provide
older gcc.

Thanks,
Qu

> 
>> ---
>>  utils.c | 30 ++++++++++++++++++++++--------
>>  1 file changed, 22 insertions(+), 8 deletions(-)
>>
>> diff --git a/utils.c b/utils.c
>> index a310300829eb..b274f46fdd9d 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -1134,15 +1134,25 @@ int pretty_size_snprintf(u64 size, char *str, size_t 
>> str_size, unsigned unit_mod
>>      num_divs = 0;
>>      last_size = size;
>>      switch (unit_mode & UNITS_MODE_MASK) {
>> -    case UNITS_TBYTES: base *= mult; num_divs++;
>> -    case UNITS_GBYTES: base *= mult; num_divs++;
>> -    case UNITS_MBYTES: base *= mult; num_divs++;
>> -    case UNITS_KBYTES: num_divs++;
>> -                       break;
>> +    case UNITS_TBYTES:
>> +            base *= mult;
>> +            num_divs++;
>> +            __attribute__ ((fallthrough));
>> +    case UNITS_GBYTES:
>> +            base *= mult;
>> +            num_divs++;
>> +            __attribute__ ((fallthrough));
>> +    case UNITS_MBYTES:
>> +            base *= mult;
>> +            num_divs++;
>> +            __attribute__ ((fallthrough));
>> +    case UNITS_KBYTES:
>> +            num_divs++;
>> +            break;
>>      case UNITS_BYTES:
>> -                       base = 1;
>> -                       num_divs = 0;
>> -                       break;
>> +            base = 1;
>> +            num_divs = 0;
>> +            break;
>>      default:
>>              if (negative) {
>>                      s64 ssize = (s64)size;
>> @@ -1907,13 +1917,17 @@ int test_num_disk_vs_raid(u64 metadata_profile, u64 
>> data_profile,
>>      default:
>>      case 4:
>>              allowed |= BTRFS_BLOCK_GROUP_RAID10;
>> +            __attribute__ ((fallthrough));
>>      case 3:
>>              allowed |= BTRFS_BLOCK_GROUP_RAID6;
>> +            __attribute__ ((fallthrough));
>>      case 2:
>>              allowed |= BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
>>                      BTRFS_BLOCK_GROUP_RAID5;
>> +            __attribute__ ((fallthrough));
>>      case 1:
>>              allowed |= BTRFS_BLOCK_GROUP_DUP;
>> +            __attribute__ ((fallthrough));
>>      }
>>  
>>      if (dev_cnt > 1 && profile & BTRFS_BLOCK_GROUP_DUP) {
>>

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