RFR: 8232084: HotSpot build failed with GCC 9.2.1

[Yasumasa Suenaga]

On 2019/10/17 12:49, David Holmes wrote:
> On 17/10/2019 12:45 pm, Yasumasa Suenaga wrote:
>> On 2019/10/17 11:39, David Holmes wrote:
>>> On 17/10/2019 12:19 pm, Yasumasa Suenaga wrote:
>>>> On 2019/10/17 9:34, David Holmes wrote:
>>>>> On 17/10/2019 10:07 am, serguei.spitsyn at oracle.com wrote:
>>>>>> Hi Yasumasa,
>>>>>>
>>>>>> It looks good.
>>>>>> One tip:
>>>>>>
>>>>>> + // This code would be warned as "stringop-truncation" by GCC 8 or later.
>>>>>> +PRAGMA_DIAG_PUSH
>>>>>> +PRAGMA_STRINGOP_TRUNCATION_IGNORED
>>>>>>         strncpy(buf, str, len);
>>>>>> +PRAGMA_DIAG_POP
>>>>>>
>>>>>>
>>>>>> I'd suggest to place the comment before the line with strncopy().
>>>>>
>>>>> I'd suggest just dropping the comment as it adds nothing, further gcc 8 is not flagging this use of strncpy.
>>>>
>>>> The comment is suggested in [1].
>>>> Indeed stringop-truncation warning was not reported by GCC 8, but this option introduced in it,
>>>> and I agree with Ioi to add the comment for other developers why this #pragma is needed.
>>>
>>> PRAGMA_STRINGOP_TRUNCATION_IGNORED
>>>
>>> seems to pretty clearly state what the issue is to me. But if you want to add a comment to make that more clear fine. But don't mention gcc 8 as it is not relevant to the need for the pragma now.
>>
>> I'd like to change the comment as below:
>>
>>      This code would be warned as "stringop-truncation" by modern GCC
>>
>> Is it ok?
> 
> Grammatically it needs work. I propose
> 
> // This code can cause a "stringop-truncation" warning with gcc
> 
> "modern" will become inaccurate as time goes by.

Thanks!
To be clear that our code is correct, I will change the comment as below:

   // This code can cause a "stringop-truncation" warning with gcc incorrectly


Yasumasa


> Thanks,
> David
> 
>>
>> Yasumasa
>>
>>
>>> Thanks,
>>> David
>>>
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> [1] https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-October/029578.html
>>>>
>>>>> Otherwise okay.
>>>>>
>>>>> Thanks,
>>>>> David
>>>>>
>>>>>> Not  subject for re-review.
>>>>>>
>>>>>> Thanks,
>>>>>> Serguei
>>>>>>
>>>>>>
>>>>>> On 10/16/19 16:25, Yasumasa Suenaga wrote:
>>>>>>> (Re-send email because I could not send original email to serviceability-dev and hotspot-compiler-dev)
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> We discussed the fix for JDK-8232084 in [1], and I think we should fix it with #pragma.
>>>>>>> I uploaded new webrev. Could you review it?
>>>>>>>
>>>>>>>   JBS: https://bugs.openjdk.java.net/browse/JDK-8232084
>>>>>>>   webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8232084/webrev.03/
>>>>>>>
>>>>>>> This change has passed the tests on submit repo (mach5-one-ysuenaga-JDK-8232084-1-20191016-1534-5969882).
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Yasumasa
>>>>>>>
>>>>>>>
>>>>>>> [1] https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-October/029547.html
>>>>>>