signal handler sa_sigaction arguments

Question

i have

struct sigaction pipe_act;
pipe_act.sa_flags = SA_SIGINFO;
pipe_act.sa_sigaction = sigpipehandler
sigaction(SIGPIPE, &pipe_act, NULL);

when i've try to write the sigpipeHandler, gcc told me that it needs three args. The second args is ok, it's siginfo_t struct that containts information about signal, bue the first and the third (an int and a void variable), what are they?

Answer 1

The man of sigaction says :

 The sigaction structure is defined as something like:

       struct sigaction {
           void     (*sa_handler)(int);
           void     (*sa_sigaction)(int, siginfo_t *, void *);
           sigset_t   sa_mask;
           int        sa_flags;
           void     (*sa_restorer)(void);
       };  

   sa_handler specifies the action to be associated with signum and may be
   SIG_DFL for the default action, SIG_IGN to ignore  this  signal,  or  a
   pointer to a signal handling function.  This function receives the sig‐
   nal number as its only argument.

   If SA_SIGINFO is specified in sa_flags, then sa_sigaction  (instead  of
   sa_handler)  specifies  the  signal-handling function for signum.  This
   function receives the signal number as its first argument, a pointer to
   a  siginfo_t as its second argument and a pointer to a ucontext_t (cast
   to void *) as its third argument.


   ....

   The siginfo_t argument to sa_sigaction is a struct with  the  following
   elements:

       siginfo_t {
           int      si_signo;    /* Signal number */
           int      si_errno;    /* An errno value */
           int      si_code;     /* Signal code */
           int      si_trapno;   /* Trap number that caused
                                    hardware-generated signal
                                    (unused on most architectures) */
           pid_t    si_pid;      /* Sending process ID */
           uid_t    si_uid;      /* Real user ID of sending process */
           int      si_status;   /* Exit value or signal */
           clock_t  si_utime;    /* User time consumed */
           clock_t  si_stime;    /* System time consumed */
           sigval_t si_value;    /* Signal value */
           int      si_int;      /* POSIX.1b signal */
           void    *si_ptr;      /* POSIX.1b signal */
           int      si_overrun;  /* Timer overrun count; POSIX.1b timers */
           int      si_timerid;  /* Timer ID; POSIX.1b timers */
           void    *si_addr;     /* Memory location which caused fault */
           long     si_band;     /* Band event (was int in
                                    glibc 2.3.2 and earlier) */
           int      si_fd;       /* File descriptor */
           short    si_addr_lsb; /* Least significant bit of address
                                    (since kernel 2.6.32) */
       }