NullPointerException with cpp2 after va_arg

[mpivet-p]

I have the following error when running JPlag on a C file using the cpp2 language parameter:

$> java -jar ~/Downloads/jplag-4.3.0-jar-with-dependencies.jar -l cpp2 check
2024-02-21-06:24:37_092 [main] [INFO] LanguageLoader - Available languages: '[C/C++ Scanner [basic markup], C/C++ Parser, C# 6 Parser, EMF metamodel, Go Parser, Javac based AST plugin, Kotlin Parser, Python3 Parser, R Parser, Rust Language Module, Scala parser, SchemeR4RS Parser [basic markup], Swift Parser, Text Parser (naive)]'
2024-02-21-06:24:37_102 [main] [INFO] ParallelComparisonStrategy - Start comparing...
line 3:27 no viable alternative at input 'va_arg(arg,unsignedint)'
line 3:30 mismatched input ''c'' expecting {'decltype', 'operator', '(', '*', '&', '~', AndAnd, '::', '...', Identifier}
line 3:33 extraneous input ')' expecting ';'
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.List.iterator()" because "next.children" is null
	at de.jplag.cpp2.CPPTokenListener.getDescendant(CPPTokenListener.java:375)
	at de.jplag.cpp2.CPPTokenListener.enterSimpleDeclaration(CPPTokenListener.java:326)
	at de.jplag.cpp2.grammar.CPP14Parser$SimpleDeclarationContext.enterRule(CPP14Parser.java:5639)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.enterRule(ParseTreeWalker.java:50)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:33)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
	at de.jplag.cpp2.CPPParserAdapter.scan(CPPParserAdapter.java:46)
	at de.jplag.cpp2.CPPLanguage.parse(CPPLanguage.java:48)
	at de.jplag.Submission.parse(Submission.java:249)
	at de.jplag.SubmissionSet.parseSubmissions(SubmissionSet.java:147)
	at de.jplag.SubmissionSet.parseAllSubmissions(SubmissionSet.java:103)
	at de.jplag.SubmissionSet.<init>(SubmissionSet.java:45)
	at de.jplag.SubmissionSetBuilder.buildSubmissionSet(SubmissionSetBuilder.java:78)
	at de.jplag.JPlag.run(JPlag.java:55)
	at de.jplag.cli.CLI.main(CLI.java:91)

Running it with cpp1 works just fine and doesn't throw any error.

I am running JPlag on a macbook pro m2 with the following version:

$> java -version

openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment Homebrew (build 21.0.2)
OpenJDK 64-Bit Server VM Homebrew (build 21.0.2, mixed mode, sharing)

These C files are triggering the same error:
1)

void a()
{
	f(va_arg(arg, unsigned int), c, 'c');
}

void a(void)
{
	f(va_arg(arg, unsigned int), "c");
}

But this one works without any issue:

void a(void)
{
	f(va_arg(arg, char), c);
}

[TwoOfTwelve]

This is a case that probably will never be supported by JPlag.
As far as I can tell va_arg is a macro. Macros are't supported by JPlag, as the ANTLR grammar has no support for them. In general you could get around that by evaluating macros first, then calling JPlag. In this specific case, I think the result of the macro is still a special case that doesn't fit the grammar.
If you know a way to support this case in the grammar, feel free to open a PR or an issue in the ANTLR repository.

The cases that are working are doing so only by chance, the resulting AST is still incorrect.