RFR: JDK-8200083: Bump bootjdk used for JDK 11 at Oracle to JDK 10

[Magnus Ihse Bursie]

On 2018-04-05 04:01, David Holmes wrote:
> On 5/04/2018 11:56 AM, Martin Buchholz wrote:
>> On Wed, Apr 4, 2018 at 5:03 PM, David Holmes <david.holmes at oracle.com 
>> <mailto:david.holmes at oracle.com>> wrote:
>>
>>     On 5/04/2018 7:00 AM, Jonathan Gibbons wrote:
>>
>>
>>     I have to agree. There can't be two bootJDK versions.
>>
>>
>> I have to disagree.  You could design openjdk to be buildable by any 
>> set of boot JDKs.
>> It's only the fact that javac happens to be written in java that 
>> creates a boot jdk requirement at all.
>
> The point is you can't require two different bootJDK versions. As Jon 
> said as soon as someone relies on a JDK 10 feature** you can no longer 
> use a JDK 9 boot JDK.

So why don't we do a compromise?

Let configure accept JDK 9 or JDK 10 as boot JDK. But if JDK 9 is 
selected, a warning is display that this might not work. At some point 
in time, changes may happen in javac code that will prohibit this from 
working. But up until that point, it is still possible to use JDK 9 to 
build JDK 11, so we do not hinder that upfront in configure.

This makes it clear that you are supposed to use JDK 10. But it will 
still allow the community time to adjust. And it will not hamper the 
javac development.

Reasonable?

/Magnus



>
> ** This isn't quite as broad as it sounds. Only critical bootstrapping 
> parts of the build are limited to the capabilities of the bootJDK. The 
> other parts will be built with the interim javac.
>
> David