#include <stdio.h>

#define MAX_ERRNO       4095

#define IS_ERR_VALUE(x) ((x) >= (unsigned long)-MAX_ERRNO)

static inline long IS_ERR(const void *ptr)
{
        return IS_ERR_VALUE((unsigned long)ptr);
}

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

int main(int argc, const char *argv[])
{
	void *ptr = (void *)-1;

	printf("ptr = %p, -PTR_ERR(ptr) = %ld\n\n", ptr, -PTR_ERR(ptr));

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

	return 0;
}