sigchain.h

   1 #ifndef SIGCHAIN_H
   2 #define SIGCHAIN_H
   3
   4 /**
   5  * Code often wants to set a signal handler to clean up temporary files or
   6  * other work-in-progress when we die unexpectedly. For multiple pieces of
   7  * code to do this without conflicting, each piece of code must remember
   8  * the old value of the handler and restore it either when:
   9  *
  10  *   1. The work-in-progress is finished, and the handler is no longer
  11  *      necessary. The handler should revert to the original behavior
  12  *      (either another handler, SIG_DFL, or SIG_IGN).
  13  *
  14  *   2. The signal is received. We should then do our cleanup, then chain
  15  *      to the next handler (or die if it is SIG_DFL).
  16  *
  17  * Sigchain is a tiny library for keeping a stack of handlers. Your handler
  18  * and installation code should look something like:
  19  *
  20  * ------------------------------------------
  21  *   void clean_foo_on_signal(int sig)
  22  *   {
  23  *        clean_foo();
  24  *        sigchain_pop(sig);
  25  *        raise(sig);
  26  *   }
  27  *
  28  *   void other_func()
  29  *   {
  30  *        sigchain_push_common(clean_foo_on_signal);
  31  *        mess_up_foo();
  32  *        clean_foo();
  33  *   }
  34  * ------------------------------------------
  35  *
  36  */
  37
  38 /**
  39  * Handlers are given the typedef of sigchain_fun. This is the same type
  40  * that is given to signal() or sigaction(). It is perfectly reasonable to
  41  * push SIG_DFL or SIG_IGN onto the stack.
  42  */
  43 typedef void (*sigchain_fun)(int);
  44
  45 /* You can sigchain_push and sigchain_pop individual signals. */
  46 int sigchain_push(int sig, sigchain_fun f);
  47 int sigchain_pop(int sig);
  48
  49 /**
  50  * push the handler onto the stack for the common signals:
  51  * SIGINT, SIGHUP, SIGTERM, SIGQUIT and SIGPIPE.
  52  */
  53 void sigchain_push_common(sigchain_fun f);
  54
  55 void sigchain_pop_common(void);
  56
  57 #endif /* SIGCHAIN_H */