ecj doesn't detect module conflict without specifying -source

[trancexpress]

ecj doesn't detect module conflict without specifying -source

[trancexpress]

Note that ecj produces class version 61 when it doesn't detect the module conflict:

$ /usr/lib/jvm/java-11-openjdk/bin/java -classpath TestLibraryModule.jar:TestLibraryUnnamedModule.jar:. TestConflict
Exception in thread "main" java.lang.UnsupportedClassVersionError: testpackage/TestClass has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1017)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
        at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:800)
        at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:698)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:621)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
        at TestConflict.main(TestConflict.java:3)

[trancexpress]

Maybe there is some default here? I see this source value during the compile:

org.eclipse.jdt.core.compiler.source=1.3

"main" #1 prio=5 os_prio=0 cpu=157.90ms elapsed=108.90s tid=0x00007f01e4014c60 nid=0x5f3b runnable  [0x00007f01e85fe000]
   java.lang.Thread.State: RUNNABLE
        at org.eclipse.jdt.internal.compiler.impl.CompilerOptions.versionToJdkLevel(CompilerOptions.java:874)
        at org.eclipse.jdt.internal.compiler.impl.CompilerOptions.versionToJdkLevel(CompilerOptions.java:869)
        at org.eclipse.jdt.internal.compiler.batch.Main.validateOptions(Main.java:5540)
        at org.eclipse.jdt.internal.compiler.batch.Main.configure(Main.java:3055)
        at org.eclipse.jdt.internal.compiler.batch.Main.compile(Main.java:1781)
        at org.eclipse.jdt.internal.compiler.batch.Main.main(Main.java:1521)

Calling ecj -help, that seems to be the case:

$ /usr/lib/jvm/java-17-openjdk/bin/java -jar /data/eclipses/ecj-4.27M1.jar -help 
Eclipse Compiler for Java(TM) v20221222-1640, 3.33.0
Copyright IBM Corp 2000, 2020. All rights reserved.
 
 Usage: <options> <source files | directories>
 If directories are specified, then their source contents are compiled.
 Possible options are listed below. Options enabled by default are prefixed
 with '+'.
[..]
 Compliance options:
    -1.3               use 1.3 compliance (-source 1.3 -target 1.1)
    -1.4             + use 1.4 compliance (-source 1.3 -target 1.2)
    -1.5 -5 -5.0       use 1.5 compliance (-source 1.5 -target 1.5)
    -1.6 -6 -6.0       use 1.6 compliance (-source 1.6 -target 1.6)
    -1.7 -7 -7.0       use 1.7 compliance (-source 1.7 -target 1.7)
    -1.8 -8 -8.0       use 1.8 compliance (-source 1.8 -target 1.8)
    -1.9 -9 -9.0       use 1.9 compliance (-source 1.9 -target 1.9)
    -10 -10.0          use 10  compliance (-source 10  -target 10)
    -11 -11.0          use 11  compliance (-source 11  -target 11)
    -12 -12.0          use 12  compliance (-source 12  -target 12)
    -13 -13.0          use 13  compliance (-source 13  -target 13)
    -14 -14.0          use 14  compliance (-source 14  -target 14)
    -15 -15.0          use 15  compliance (-source 15  -target 15)
    -16 -16.0          use 16  compliance (-source 16  -target 16)
    -17 -17.0          use 17  compliance (-source 17  -target 17)
    -18 -18.0          use 18  compliance (-source 18  -target 18)
    -19 -19.0          use 19  compliance (-source 19  -target 19)
    -source <version>  set source level: 1.3 to 1.9, 10 to 19
                       (or 6, 6.0, etc)
    -target <version>  set classfile target: 1.3 to 1.9, 10 to 19
                       (or 6, 6.0, etc)
                       cldc1.1 can also be used to generate the StackMap
                       attribute

[trancexpress]

Seems fine then. -source 1.3 sounds quite outdated as a default, but its documented and changing it is maybe not the best idea.

For completeness, javac seems to use the JDK version as default:

https://docs.oracle.com/en/java/javase/17/docs/specs/man/javac.html

--source release or -source release

    Compiles source code according to the rules of the Java programming language for the specified Java SE release. The supported values of release are the current Java SE release and a limited number of previous releases, detailed in the command-line help.

    If the option is not specified, the default is to compile source code according to the rules of the Java programming language for the current Java SE release.