Variadic macros with zero arguments

As for the updated question, by the use of auxiliary macro VA_ARGS like the following, the arguments will be expanded as expected.

#define VA_ARGS(...) , ##__VA_ARGS__
#define CALL(f,...) FN(f)->call((ref(new LinkedList()) VA_ARGS(__VA_ARGS__)))

If you're using gcc/g++ there is a way:

#define CALL(f,...) FN(f)->call((ref(new LinkedList()), ## __VA_ARGS__))

From the fine manual:

[...] if the variable arguments are omitted or empty, the `##' operator causes the preprocessor to remove the comma before it.

So gcc has an extension/hack specifically for the problem you are facing.

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