Public bug reported:

[Impact]

openjdk-9 introduced a few api changes that result in runtime errors
when trying to run the java classes under openjdk 8 (or earlier) even
when -source/-target are properly set.

The fix is to build such code using the new openjdk-9 flag "--release"
instead of the "-source/-target" pair.

When running Cosmic's jtreg 4.2-b13-1 with agentvm under openjdk-8 it will fail 
and output a few lines such as:
stderr: Exception: java.lang.NoSuchMethodError thrown from the 
UncaughtExceptionHandler in thread "main"

The java.lang.NoSuchMethodError is actually caused by
"java.lang.NoSuchMethodError:
java.nio.ByteBuffer.flip()Ljava/nio/ByteBuffer" which can be easily
solved by building jtreg with the "--release 7" argument.


[Test Case]
For this test case we need to create an empty TEST.ROOT file and a test class 
to satisfy jtreg requirements of a minimum test. jtreg must also be forced to 
use openjdk-8.

$ sudo apt install openjdk-8-jdk jtreg
$ touch TEST.ROOT
$ cat > Hello.java << EOF
/*
 * @test
 * @bug 2718282
 * @summary Hello test
 */

public class Hello {
    public static void main(String [] args) throws Exception {
        if (true)
            System.out.println("Hello World!");
        else
            throw new Exception("??");
    }
}
EOF
$ JT_JAVA=/usr/lib/jvm/java-8-openjdk-amd64/ jtreg -va -agentvm Hello.java 
[2018-11-15 23:42:34,720] Agent[0]: stderr: 
[2018-11-15 23:42:34,721] Agent[0]: stderr: Exception: 
java.lang.NoSuchMethodError thrown from the UncaughtExceptionHandler in thread 
"main"
--------------------------------------------------
TEST: Hello.java
TEST JDK: /usr/lib/jvm/java-8-openjdk-amd64
[snipped]
Test results: error: 1
Report written to /tmp/JTreport/html/report.html
Results written to /tmp/JTwork
Error: Some tests failed or other problems occurred.


The expected response from jtreg does not contain the "stderr:" lines as in:
$ JT_JAVA=/usr/lib/jvm/java-8-openjdk-amd64/ jtreg -va -agentvm Hello.java 
--------------------------------------------------
TEST: Hello.java
TEST JDK: /usr/lib/jvm/java-8-openjdk-amd64
[snipped]
Test results: passed: 1
Report written to /tmp/JTreport/html/report.html
Results written to /tmp/JTwork

Alternatively one can also check that openjdk-lts is not affected by the 
change, it should output the same before and after the fix:
$ sudo apt install openjdk-11-jdk
$ JT_JAVA=/usr/lib/jvm/java-11-openjdk-amd64/ jtreg -va -agentvm Hello.java 
--------------------------------------------------
TEST: Hello.java
TEST JDK: /usr/lib/jvm/java-11-openjdk-amd64
[snipped]
Test results: passed: 1
Report written to /tmp/JTreport/html/report.html
Results written to /tmp/JTwork


[Regression Potential]
1. The --release argument is jdk9+ only, if jtreg is ever build with an older 
jdk it will FTBFS, so this change should only be backported on releases where 
the default-jdk is 9+. 
2. The --release N argument is equivalent to setting -source N/-target 
N/-bootclasspath <N bootclasspath>, which can cause issues if the compiled 
classes use APIs that have been removed or are considered internal. The current 
jtreg version does not rely on internal classes from jdk 8 (otherwise it would 
FTBFS) but if a later version does that it will probably FTBFS - note that this 
is very unlikely as it would mean that upstream decided to break building jtreg 
with newer jdks.


[Other Info]
See https://github.com/apache/felix/pull/114 for a good overview on the methods 
that changed on OpenJDK 9 and a better description on the cause. Note that they 
propose patching the methods to cast ByteBuffer to Buffer when calling the 
affected methods, but this can be easily prevented by using the --release 
argument instead.

** Affects: jtreg (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1803628

Title:
  jtreg fails due to api incompatibility with openjdk-9 or later

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