Initial JDK 11 RFR of JDK-8173382: Add -source 11 and -target 11 to javac - Java Bug System & JDK-8193291: Add SourceVersion.RELEASE_11

[joe darcy]

Hi David,


On 12/12/2017 1:32 PM, David Holmes wrote:
> Hi Joe,
>
> On 13/12/2017 7:27 AM, joe darcy wrote:
>> Hi David,
>>
>>
>> On 12/12/2017 1:11 PM, David Holmes wrote:
>>> Hi Joe,
>>>
>>> On 12/12/2017 5:04 PM, joe darcy wrote:
>>>> Hello,
>>>>
>>>> With the JDK 11 line of development opening up in a few days, a few 
>>>> changes are needed to prepared to turn a JDK 10 code base into a 
>>>> JDK 11 one including:
>>>>
>>>>      JDK-8173382: Add -source 11 and -target 11 to javac
>>>>      JDK-8193291: Add SourceVersion.RELEASE_11
>>>>
>>>>      Webev:
>>>>          http://cr.openjdk.java.net/~darcy/8173382.1/
>>>>      CSRs:
>>>>          JDK-8193350: Add -source 11 and -target 11 to javac
>>>>          JDK-8193351: Add SourceVersion.RELEASE_11
>>>>
>>>> Please review the preliminary webrev and CSRs.
>>>
>>> I don't see a change to the actual JDK version as part of this ?? 
>>
>> Correct; the webrev to date is the langtools portion of the new JDK 
>> groundbreaking, the same subset of groundbreaking I looked at for the 
>> 9 -> 10 transition. Other pieces are needed too, including HotSpot 
>> changes and the actual version update.
>
> So what is the overall transition strategy here? I don't see how you 
> can change javac to default to -source/-target 11 prior to bumping the 
> actual version to 11. Or do you expect all the additional pieces to 
> come together at the same time?
>

For background, what we've done in the past is at the very start of a 
new JDK release, first create -source/-target ${N+1} that begin as 
aliases for ${N} and are the default -source/-target for javac. [1] As 
new language features are developed, the javac implementation adds 
allowFeatureFoo() predicates which turn into

     return sourceOptionBeingUsed >= firstSourceWhichAllowsFeature

So the operational distinction between -source ${N} and -source ${N+1} 
comes about after language changes have been made for release ${N+1}. 
For -target, since there is often not a hard dependency between new Java 
language features and JVM features, an operational distinction between 
successive values of -target, and thus successive class file versions, 
can come about later in the release. For example, in JDK 10 the language 
feature var/local variable type inference enabled by -source 10 was in 
JDK 10 builds a few months before -target 10 mapped to an updated class 
file version.

We could follow the same path for the JDK 10 -> 11 transition. Paul has 
suggested also updating the class file version at the same time this 
time around.

HTH,

-Joe

[1] Way back when, the new -source/-target values were added without 
simultaneously being made the default. This increased maintenance costs 
of javac tests and led us to implement the current policy.