#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include "signal_support.h"

volatile sig_atomic_t should_exit;
volatile sig_atomic_t signal_pending;
volatile sig_atomic_t signal_isblocked;

void alarm_went_off(int sig, siginfo_t *info, void *_context);

static void
fast_block()
{
    signal_isblocked++;
}

static void
fast_unblock()
{
    if (--signal_isblocked == 0 && signal_pending) {
        alarm_went_off(SIGALRM, NULL, NULL);
    }
}

void 
alarm_went_off(int sig, siginfo_t *info, void *_context)
{
    if (signal_isblocked) {
        signal_pending = 1;
        return;
    }
    signal_pending = 0;
    // ----------------------------------------

    printf("Alarm went off\n");
    should_exit = 1;
}

int
main()
{
    signal_set_handler(SIGALRM, alarm_went_off);
    alarm(3);

    printf("main program running...\n");
    while (!should_exit) {
        for (int i = 0; i < 300000000; i++) {
            volatile int sqi = i * i;
        }
        fast_block();
        printf("main program here...\n");
        fast_unblock();
    }
    printf("main program done...\n");
}