On 5/18/20 1:32 PM, Guoqing Jiang wrote:
> On 5/18/20 7:22 PM, Jes Sorensen wrote:
>> On 5/15/20 9:40 AM, Guoqing Jiang wrote:
>>> Got below error when run "make everything".
>>>
>>> restripe.c: In function ‘test_stripes’:
>>> restripe.c:870:4: error: ignoring return value of ‘read’, declared
>>> with attribute warn_unused_result [-Werror=unused-result]
>>> read(source[i], stripes[i], chunk_size);
>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Fix it by set the return value of ‘read’ to diskP, which should be
>>> harmless since diskP will be set again before it is used.
>>>
>>> Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
>>> ---
>>> restripe.c | 6 +++++-
>>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/restripe.c b/restripe.c
>>> index 31b07e8..21c90f5 100644
>>> --- a/restripe.c
>>> +++ b/restripe.c
>>> @@ -867,7 +867,11 @@ int test_stripes(int *source, unsigned long long
>>> *offsets,
>>> for (i = 0 ; i < raid_disks ; i++) {
>>> lseek64(source[i], offsets[i]+start, 0);
>>> - read(source[i], stripes[i], chunk_size);
>>> + /*
>>> + * To resolve "ignoring return value of ‘read’", it
>>> + * should be harmless since diskP will be again later.
>>> + */
>>> + diskP = read(source[i], stripes[i], chunk_size);
>> It doesn't complain on Fedora 32, however checking the return value of
>> lseek64 and read is a good thing.
>>
>> However what you have done is to just masking the return value and
>> throwing it away, is not OK. Please do it properly.
>
> Yes, it is used to suppress the warning. And set the return value to a
> new variable
> could cause unused-but-set-variable, not sure if there is better way now.
The correct way is to check the return values and take appropriate
action if an error is returned.
Jes
