信号处理器sa_sigaction参数

Question

我有

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

当我尝试写sigpipeHandler，GCC告诉我，它需要三个参数。第二个参数是好的，它是siginfo_t结构，它包含有关信号的信息，第一个和第三个（一个int和一个void变量），它们是什么？

Answer 1

第一个参数是信号编号。这是必要的，因为你可以使用相同的处理程序来处理几个不同的信号

第三个参数包含接收信号时正在使用的上下文。可以通过makecontext()/setcontext()/getcontext()/swapcontext()函数使用上下文来实现用户空间线程。上下文结构还包含非便携式体系结构特定信息，例如，处理器在收到信号时寄存器的值。与处理器状态混淆需要您自担风险。

Answer 2

的sigaction的人说：

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) */ 
     }