int main() {
#ifdef NOT_DEFINED
	if (true) {
		//...
	}
	else {
		//...
	}
#else
	if (true) {
		//...
	}
#endif
}

In this file, the main function only folds the first line. The comments in the if/else blocks in the NOT_DEFINED region can fold to the next line, and the else block can fold to the end of the function.