RFR(T): 8233530: gcc 5.4 build warning -Wc++14-compat after JDK-8233359

[David Holmes]

I was surprised to see this got pushed before Kim had had a chance to 
respond and when there was apparently still an open question to me. :(

And now we see it breaks gcc 4.8.5.

David

On 6/11/2019 3:37 pm, Kim Barrett wrote:
>> On Nov 5, 2019, at 8:44 PM, David Holmes <david.holmes at oracle.com> wrote:
>>
>> On 6/11/2019 11:38 am, Kim Barrett wrote:
>>>> On Nov 5, 2019, at 2:06 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> may I please have reviews for this small build fix:
>>>>
>>>> Issue: https://bugs.openjdk.java.net/browse/JDK-8233530
>>>> Webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8233530-wc14-compat/webrev.00/webrev/
>>>> Prior discussion: https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-November/036726.html
>>>>
>>>> Thank you,
>>>>
>>>> Thomas
>>> The "#ifdef __GNUG__" should not be needed or used.
>>> There are a dozen existing uses of PRAGMA_DIAG_PUSH.
>>> While there aren't currently any other direct uses of
>>> PRAGMA_DISABLE_GCC_WARNING, there are indirect uses via other
>>> PRAGMA_DISABLE_xxx macros.
>>> None of those have __GNUX__ protections (for any X).
>>
>> Well AFAICS they reside in a gcc specific file: compilerWarnings_gcc.hpp. But we also take steps in compilerWarnings.hpp to accommodate their use in source code when other compilers are used.
>>
>> #ifndef PRAGMA_DISABLE_GCC_WARNING
>> #define PRAGMA_DISABLE_GCC_WARNING(name)
>> #endif
>>
>> so I agree we should not need any guard to make this gcc only - unless we really do want to control the version.
> 
> If we need to control the version it’s applied to, we can use PRAGMA_STRINGOP_TRUNCATION_IGNORED as a model.
> Or just version-conditionalize at the one place it’s needed, for now.  If more -Wc++14-compat issues come up later
> then we can introduce a new macro.
> 
>