RFR: 8357119: Make Zero the default and only variant of HotSpot for iOS [v2]

[Johan Vos]

On Sat, 17 May 2025 04:07:40 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>>> @johanvos How can you test if you are building for the device or an emulator?
>>> 
>>> If this can/should be supported, then we also need to write something about it in the documents, not only update configure.
>>> 
>>> And if we can't detect the difference, then maybe most of this PR will need to be scrapped.
>> 
>> That is defined in the sysroot that is passed with configure. If you provide
>> `--with-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk` you are building for the device.
>> 
>> If you provide
>> `--with-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/`
>> you are building the the simulator.
>> 
>> If the latter SDK is selected, `#ifdef TARGET_OS_SIMULATOR` will return true when compiling code. (but that won't help for the makefiles to detect if we're building for device or simulator)
>
>> @johanvos How can you test if you are building for the device or an emulator?
>> 
>> If this can/should be supported, then we also need to write something about it in the documents, not only update configure.
>> 
>> And if we can't detect the difference, then maybe most of this PR will need to be scrapped.
> 
> I still think defaulting to Zero for iOS is helpful, but I can remove the restricting of valid iOS JVM variants to only Zero since that is problematic.

@TheShermanTanker can you make the change in the PR title (and corresponding JBS issue) as Magnus requested? Once that is done, you can integrate the PR.
Thanks!

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PR Comment: https://git.openjdk.org/mobile/pull/35#issuecomment-2908900624