Evidence of incompatibility (was Some suggested patches and improvements)

Robert Gibson robbiexgibson at yahoo.com
Wed May 17 19:56:15 UTC 2017

On 17 May 2017, at 20:50, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> On 17/05/2017 18:26, Eric Johnson wrote:
>> :
>> Here's a challenge back to the Jigsaw team. Can I still do java -jar ...
>> every existing Java application (without recompile!) that currently
>> launches that way? I'm even willing to cut some slack and ignore
>> applications that use com.sun APIs that have been "private" for years. Will
>> that still work? The Jigsaw community should be able to provide evidence
>> that's still possible, not that we should be required to provide evidence
>> that it isn't.
> FWIW, the JDK has never been able to guarantee this at major releases. A typical JDK major release will have ~20000 changes that translate into a lot of code so there is a lot of potential for breakage or subtle behavior or performance changes. Even mundane things like rev'ing the class file version at every major release can be disruptive. Nothing to do with Project Jigsaw but there are many one-off changes in JDK 9 that will make it more disruptive than previous releases, e.g. moving to G1 as the default collector, switching to use CDLR locale data by default, the new version-string scheme, changes to the layout of the run-time image, .... it's a long list that will eventually show up as extensive release and compatibility notes.

And of course the intersection of these issues makes things even more complicated.  At this point I would settle for being able to add a command-line flag to get our app to run, but despite testing EA builds for over a year and assiduously flagging issues as we came across them it’s still not possible for us (intersection of CLDR change and Webstart)

Low-energy rant ends here in resignation,

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