#include <stdio.h>

static inline long PTR_ERR(const void *ptr)
{
	return (long) ptr;
}

int main(int argc, const char *argv[])
{
	printf("sizeof(char) = %lu, sizeof(int) = %lu, sizeof(long) = %lu\n\n",
			sizeof(char), sizeof(int), sizeof(long));

	/*This address is in kernel space, check Documentation/x86/x86_64/mm.txt*/
	void *ptr = (void *)0Xffff8900f0000000;

	printf("ptr = %p, PTR_ERR(ptr) = %lx, (int)(-PTR_ERR(ptr)) = %d\n\n",
			ptr, PTR_ERR(ptr), (int)(-PTR_ERR(ptr)));

	if ((int)(-PTR_ERR(ptr)) < 0)
		printf("That's what the codes want.\n");
	else
		printf("Bug happens!\n");

	return 0;
}