• 15.6.2 Argument substitution [cpp.subst]/4 - eel.is

Here is an example of H3.

#define H3(X, ...) #__VA_OPT__(X##X X##X)
H3(, 0)             // replaced by ""

On the other hand, just below that is:

Each # preprocessing token in the replacement list for a function-like macro shall be followed by a parameter as the next preprocessing token in the replacement list.

This is inconsistent and I think the code example is wrong, but what about?

When I run it, it seems to reject everything except clang.

• CompilerExplorer