Reactor extending itself causes StackOverflowError

[housengw]

minimal example

target C;
reactor A extends A {}

output

wonghouseng@beefy-desktop-linux:~/Desktop/lingua-franca/test/C$  lfc src/exp.lf
0    [main] ERROR text.validation.CompositeEValidator  - Error executing EValidator
java.lang.StackOverflowError
	at org.eclipse.emf.ecore.util.EcoreEList.resolveProxy(EcoreEList.java:206)
	at org.eclipse.emf.ecore.util.EcoreEList.resolve(EcoreEList.java:161)
	at org.eclipse.emf.ecore.util.EObjectResolvingEList.resolve(EObjectResolvingEList.java:60)
	at org.eclipse.emf.common.util.BasicEList.get(BasicEList.java:348)
	at org.eclipse.emf.common.util.AbstractEList$EIterator.doNext(AbstractEList.java:698)
	at org.eclipse.emf.common.util.AbstractEList$EIterator.next(AbstractEList.java:685)
	at org.lflang.ASTUtils.allParameters(ASTUtils.java:615)
	at org.lflang.ASTUtils.allParameters(ASTUtils.java:616)
...
	at org.lflang.ASTUtils.allParameters(ASTUtils.java:616)
lfc: fatal error: An unexpected error occurred:
java.lang.NullPointerException
	at org.lflang.FileConfig.toIPath(FileConfig.java:707)
	at org.lflang.FileConfig.toPath(FileConfig.java:690)
	at org.lflang.lfc.Main.getValidatedResource(Main.java:336)
	at org.lflang.lfc.Main.runGenerator(Main.java:271)
	at org.lflang.lfc.Main.main(Main.java:209)

[edwardalee]

This is because InstantiationGraph no longer detects cycles. Perhaps because of porting to Java?

[housengw]

ok, based on results gathered from inserting print statements, seems like ASTUtils.allParameters is called before LFValidator.checkReactor is called and InstantiationGraph is initialized, and since allParameters is recursive, it causes a stack overflow before any checks take place.

Below is the function allParameters.
definition.getSuperClasses() will always be the same reactor if the reactor extends itself.

public static List<Parameter> allParameters(Reactor definition) {
        List<Parameter> result = new ArrayList<>();
        List<ReactorDecl> superClasses = convertToEmptyListIfNull(definition.getSuperClasses());
        for (ReactorDecl base : superClasses) {
            result.addAll(allParameters(toDefinition(base)));
        }
        result.addAll(definition.getParameters());
        return result;
    }

[edwardalee]

The situation is even worse than this. Not only are circular extensions not detected, but when multiple extensions include duplicates, the result is invalid. For example, then following reactor foo ends up having 5 input ports, two of which have the same name, rather than the correct four inputs.

target C;

reactor D {
    input d:int;
}
reactor C extends D {
    input c:int;
}
reactor B extends D {
    input b:int;
}
reactor A extends B, C {
    input a:int;
}

main reactor {
    foo = new A();
}

I'm working on a fix.

[edwardalee]

These two problems should be solved with PR #962.