gistfile1.c

#include <signal.h>
#include <stdio.h>
#include <malloc.h>
#include <setjmp.h>
#include <stdbool.h>

static jmp_buf omg;

struct list {
	char dummy[16384];
	struct list *next;
};

static void handler(int sig, siginfo_t *si, void *unused)
{
	longjmp(omg, 1);
}

bool list_cycle(struct list *list)
{
	struct sigaction sa;
	struct sigaction old;
	struct list *prev;

	sa.sa_flags = SA_SIGINFO;
	sigemptyset(&sa.sa_mask);
	sa.sa_sigaction = handler;
	if (sigaction(SIGABRT, &sa, &old) == -1) {
		perror("sigaction");
		return -1;
	}

	if (setjmp(omg)) {
		if (sigaction(SIGABRT, &old, NULL) == -1) {
			// perror("sigaction"); // ignore
		}
		return true;
	}

	while (list->next) {
		prev = list;
		list = list->next;
		free(prev);
	}
	free(list);

	if (sigaction(SIGABRT, &old, NULL) == -1) {
		perror("sigaction");
		return -1;
	}
	return false;
}

int main (int argc, char **argv) {
	struct list *test, *test2;

	test = malloc(sizeof(struct list));
	test2 = malloc(sizeof(struct list));
	test->next = test2;
	test2->next = test;

	if (list_cycle(test) == true) {
		printf("loop\n");
	} else {
		printf("no loop\n");
	}
}