memcheck/tests/freebsd/sigwait.c

   1 #include <signal.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <assert.h>
   5
   6 // from stack overflow
   7 // https://stackoverflow.com/questions/6326290/about-the-ambiguous-description-of-sigwait
   8 // except the deliberate errors
   9
  10 static int sig_count;
  11
  12 void on_sigusr1(int sig)
  13 {
  14     ++sig_count;
  15 }
  16
  17 int main(void)
  18 {
  19   // Set a signal handler for SIGUSR1
  20   signal(SIGUSR1, &on_sigusr1);
  21
  22   // At program startup, SIGUSR1 is neither blocked nor pending, so raising it
  23   // will call the signal handler
  24   raise(SIGUSR1);
  25
  26   // Now let's block SIGUSR1
  27   sigset_t* psigset = malloc(sizeof(sigset_t));
  28   sigemptyset(psigset);
  29   sigaddset(psigset, SIGUSR1);
  30   sigprocmask(SIG_BLOCK, psigset, NULL);
  31
  32   // SIGUSR1 is now blocked, raising it will not call the signal handler
  33   raise(SIGUSR1);
  34
  35   // SIGUSR1 is now blocked and pending -- this call to sigwait will return
  36   // immediately
  37   int sig;
  38   int result = sigwait(psigset, &sig);
  39   if(result == 0)
  40     printf("sigwait got signal: %d\n", sig);
  41
  42   // SIGUSR1 is now no longer pending (but still blocked).  Raise it again and
  43   // unblock it
  44   raise(SIGUSR1);
  45   printf("About to unblock SIGUSR1\n");
  46   sigprocmask(SIG_UNBLOCK, psigset, NULL);
  47   printf("Unblocked SIGUSR1\n");
  48
  49   assert(sig_count == 2);
  50
  51   // now a couple of bad params
  52   // reblock
  53   sigprocmask(SIG_BLOCK, psigset, NULL);
  54   raise(SIGUSR1);
  55
  56   int* psig = malloc(sizeof(int));
  57   free(psig);
  58   result = sigwait(psigset, psig);
  59
  60   free(psigset);
  61
  62   raise(SIGUSR1);
  63
  64   result = sigwait(psigset, &sig);
  65
  66   return 0;
  67 }
  68