lib/ansi/signal.c

   1 /* SYSVR4 and ANSI compatible signal(2). */
   2
   3 #include <lib.h>
   4 #define sigaction       _sigaction
   5 #define sigemptyset     _sigemptyset
   6 #include <signal.h>
   7
   8 PUBLIC sighandler_t signal(sig, disp)
   9 int sig;                        /* signal number */
  10 sighandler_t disp;              /* signal handler, or SIG_DFL, or SIG_IGN */
  11 {
  12   struct sigaction sa, osa;
  13
  14   if (sig <= 0 || sig > _NSIG || sig == SIGKILL) {
  15         errno = EINVAL;
  16         return(SIG_ERR);
  17   }
  18   sigemptyset(&sa.sa_mask);
  19
  20 #ifdef WANT_UNRELIABLE_SIGNALS
  21   /* Allow the signal being handled to interrupt the signal handler. */
  22   sa.sa_flags = SA_NODEFER;
  23
  24   /* When signal is caught, reset signal handler to SIG_DFL for all but
  25    * SIGILL and SIGTRAP.
  26    */
  27   if (sig != SIGILL && sig != SIGTRAP) sa.sa_flags |= SA_RESETHAND;
  28 #else
  29   sa.sa_flags = 0;
  30 #endif
  31
  32   sa.sa_handler = disp;
  33   if (sigaction(sig, &sa, &osa) < 0) return(SIG_ERR);
  34   return(osa.sa_handler);
  35 }