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From: =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne@vajhoej.dk>
Newsgroups: comp.lang.java.programmer
Subject: Re: Problem compiling with 9 for 8
Date: Mon, 2 Oct 2017 20:12:45 -0400
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On 10/2/2017 8:03 PM, Arne Vajhøj wrote:
> On 10/2/2017 7:46 PM, Arne Vajhøj wrote:
>> As I explained then I believe that --release replaces -source (that
>> set the language itself version), -target (that set the generated Java
>> byte code version) and -Xbootclasspath (that set the javart.jar used
>> and therefore the version used).
> 
> I found the documentation:
> 
> https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-7744EF96-5899-4FB2-B34E-86D49B2E89B6 
> 
> 
> <quote>
> The --release N flag is conceptually a macro for:
> 
> -source N -target N -bootclasspath $PATH_TO_rt.jar_FOR_RELEASE_N
> </quote>

But I was wrong about the implementation.

It does not use the old rt.jar.

https://bugs.openjdk.java.net/browse/JDK-8058150

<quote>
For JDK N and --release M, M < N, signature data of the documented APIs 
of release M of the platform is needed. This data is stored in the 
$JDK_ROOT/lib/ct.sym file, which is similar, but not the same, as the 
file of the same name in JDK 8. The ct.sym file is a ZIP file containing 
stripped-down class files corresponding to class files from the target 
platform versions.
</quote>

So --release should work without the old rt.jar, but zipinfo on
ct.sym reveals that JavaFX is not included in it.

So therefore an actual old jfxrt.jar is needed.

Arne