test/stdlib/Inputs/VariadicBool/variadicBool.h - third_party/swift - Git at Google

 #include <stdarg.h>
 #include <stdio.h>
 #include <stdbool.h>

 extern int numberOfTrues(int count, va_list arguments);
	#include <stdarg.h>
	#include <stdio.h>
	#include <stdbool.h>

	extern int numberOfTrues(int count, va_list arguments);