signal_sleep.c

/* Shows clearly that program execution waits until signal handler is done. */

#include "common.h"

volatile sig_atomic_t i = 0;

void signal_handler(__attribute__((unused)) int sig) {
    char s[] = "signal_handler\n";
    write(STDOUT_FILENO, s, sizeof(s));
    i++;
    sleep(2);
    signal(sig, signal_handler);
}

int main(void) {
    signal(SIGALRM, signal_handler);
    puts("before");
    assert(i == 0);
    assert(kill(getpid(), SIGALRM) == 0);
    assert(i == 1);
    puts("after");
    assert(kill(getpid(), SIGALRM) == 0);
    assert(i == 2);
    puts("after2");
    return EXIT_SUCCESS;
}