RFR: 8295146: Clean up native code with newer C/C++ language features [v3]

[Julian Waters]

On Wed, 23 Nov 2022 04:58:38 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Out of curiosity, is there a way to get the discussion on approving the use of alignas back up? I've read through 8250269 briefly and unlike the issues that come with C++ attributes, alignas looks relatively straightforward to switch to, without much effect on existing code. Seems like a bit of a waste to leave the JBS entry sitting on the shelf to me
>> 
>>> The various MSVC-conditional direct uses of __declspec(align(N)) should probably currently be using ATTRIBUTE_ALIGNED.
>> 
>> The instances of `__declspec(align())` changed here are in the native libraries written in C, not within HotSpot itself. From what I can see at least HotSpot never uses compiler alignment attributes directly and always strictly sticks to `ATTRIBUTE_ALIGNED` (which is probably a good thing)
>
>> Out of curiosity, is there a way to get the discussion on approving the use of alignas back up? [...]
> 
> A PR to address JDK-8252584 would be welcomed by me. Just do the process for
> Style Guide changes (see the Style Guide or previous PRs for such). I don't
> expect it would be very controversial. I think the only reason it hasn't
> already happened is because nobody has gotten around to it, or felt the need
> for it.
> 
> JDK-8250269 touches a bit more code (mostly in stubGenerator_x86_64 and
> macroAssembler_x86_32), but also seems like it should be straightforward.
> 
>> > The various MSVC-conditional direct uses of __declspec(align(N)) should probably currently be using ATTRIBUTE_ALIGNED.
>> 
>> The instances of `__declspec(align())` changed here are in the native libraries written in C, not within HotSpot itself. From what I can see at least HotSpot never uses compiler alignment attributes directly and always strictly sticks to `ATTRIBUTE_ALIGNED` (which is probably a good thing)
> 
> You are right that the Windows-conditionalized uses are in non-HotSpot code.
> I missed that context when skimming through the changes.  Since Visual Studio
> is always C++ (even though the shared files are written as C), using alignas
> with appropriate conditionalization in those files should be fine.

Resolved, will address re-implementing ATTRIBUTE_ALIGNED with alignas in another Pull Request

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PR: https://git.openjdk.org/jdk/pull/11081