I think Anton is wrong. Since C89 and before C23 calling an `int f();` function with arguments not matching the definition's actuals is UB. In C23 `int f();` became the same as `int f(void);`, so calling that function with any arguments is a compile-time error.

For variadic functions, if you use `va_start()`/`va_arg()`/`va_end()` to consume all the arguments, and leave no `va_list` alive, then the compiler can correctly generate a tail call from such functions.