#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <err.h>
#include <signal.h>


volatile size_t i;

void
sig(int s)
{
	printf("boom %zu\n", i);
	exit(1);
}

void
compute(unsigned char *v)
{
	int j = 0;
	for (i = 0; i < 12000; i++)
		j += v[i];
	printf("%d\n", j);
}


int main(int argc, char *argv[])
{
	int fd = open(argv[1], O_RDONLY);
	if (fd == -1)
		err(1, "open %s", argv[1]);
	
	signal(SIGSEGV, sig);
	unsigned char *v = mmap(0, 12000, PROT_READ, MAP_FILE, fd, 0);
	if (v == MAP_FAILED)
		err(1, "mmap");
	printf("go1\n");
	compute(v);
	truncate(argv[1], 0);
	printf("go2\n");
	compute(v);
	return 0;
}