#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <setjmp.h>

typedef void (*pqsigfunc) (int signo);

sigjmp_buf *PG_exception_stack;

static void
printmask(const char *labl)
{
	sigset_t sigs;
	int i;

	printf("masked signals at %s: ", labl);
	if (sigprocmask(SIG_SETMASK, NULL, &sigs) == 0)
	{
		for (i = 1; i <= 32; i++)
		{
//			if (sigs.sigset[0] & sigmask(i))
			if (sigs & sigmask(i))
				printf("%d, ", i);
		}
	}
	else
		printf("failed!");
	printf("\n");
	fflush(stdout);
}

static void
sigint_handler(int signo)
{
	printmask("sigint_handler");
	siglongjmp(*PG_exception_stack, 1);
	abort();
}

static pqsigfunc
pqsignal(int signo, pqsigfunc func)
{
	struct sigaction act,
				oact;

	act.sa_handler = func;
	sigemptyset(&act.sa_mask);
	act.sa_flags = 0;
	if (signo != SIGALRM)
		act.sa_flags |= SA_RESTART;
#ifdef SA_NOCLDSTOP
	if (signo == SIGCHLD)
		act.sa_flags |= SA_NOCLDSTOP;
#endif
	if (sigaction(signo, &act, &oact) < 0)
		return SIG_ERR;
	return oact.sa_handler;
}

void
intermediate_func(int level)
{
	do {
		sigjmp_buf *save_exception_stack = PG_exception_stack;
		sigjmp_buf local_sigjmp_buf;

		if (sigsetjmp(local_sigjmp_buf, 0) == 0)
		{
			PG_exception_stack = &local_sigjmp_buf;

			if (level > 0)
				intermediate_func(level - 1);
			else
			{
				kill(getpid(), SIGINT);
				sleep(1);
				abort();
			}
		}
		else
		{
			PG_exception_stack = save_exception_stack;

			printmask("inner longjmp catcher");
			siglongjmp(*PG_exception_stack, 1);
			abort();
		}
		PG_exception_stack = save_exception_stack;
	} while (0);
}

int
main(int argc, char **argv)
{
	sigjmp_buf	outer_sigjmp_buf;

	printmask("startup");
	pqsignal(SIGINT, sigint_handler);

	if (sigsetjmp(outer_sigjmp_buf, 1) != 0)
	{
		printmask("outer longjmp catcher");
		return 0;
	}
	PG_exception_stack = &outer_sigjmp_buf;

	intermediate_func(2);

	printmask("unexpected exit");
	return 0;
}