sigsegv-recovery.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

/* See LICENSE file for copyright and license details. */
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>


int *volatile just_null = NULL;

static jmp_buf jmpenv;


static void
sigsegv(int signo)
{
	(void) signo;

	siglongjmp(jmpenv, 1);
}


int
main(void)
{
	volatile int sum = 0;
	volatile int i;
	struct sigaction sa;

	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = &sigsegv;
	sigfillset(&sa.sa_mask);
	sigaction(SIGSEGV, &sa, NULL);

	for (i = 1; i <= 10; i++) {
		if (!sigsetjmp(jmpenv, 1)) {
			printf("%i: before null dereference\n", i);
			sum += *just_null;
		} else {
			printf("%i: after null dereference\n", i);
		}
	}

	fflush(stdout);
	return sum;
}