执行默认信号处理程序 [英] executing default signal handler

问题描述

我已经写在这里我已经注册信号处理程序的数量在Linux中不同信号的应用程序。
过程接收到该信号后，控制被转移到我已经登记的信号处理程序。在此信号处理我做了一些工作，我需要做的，然后我想叫即 SIF_DFL 默认信号处理程序或 SIG_IGN 。
然而， SIG_DFL 和 SIG_ING 都是宏分别扩大到数值0和1，这是无效的函数的地址。

I have written an application where i have registered number of signal handler for different signals in linux . After process receives the signal the control is transferred to the signal handler i had registered. In this signal handler i do some work which i need to do, and then i would like to call the default signal hander i.e SIF_DFL or SIG_IGN . However, SIG_DFL and SIG_ING are both macros which expand to numeric values 0 and 1 respectively, which are invalid function addresses.

有什么办法，我可以调用默认的操作即 SIG_DFL 或 SIG_IGN ？

IS there any way i can call default actions i.e SIG_DFL or SIG_IGN ?

为了达到效果 SIG_DFL 或 SIG_ING 我分别调用exit（1），什么也不做， 。但是，对于像 SIGSEGV信号我也想有核心转储。
一般来说，我会想我的默认行为是一样的 SIG_DFL ，而忽略行为相同 SIG_IGN ，顺便操作系统会做 。

In order to achieve the effect of SIG_DFL or SIG_ING i call exit(1) and do nothing , respectively . But for signals like SIGSEGV i also would like to have core dump . In general i would want to my default behavior to be same as SIG_DFL and ignore behavior same SIG_IGN , the way Operating system would do .

推荐答案

的GNU C库参考手册有一整章解释有关的信号处理一切。

The GNU C Library Reference Manual has a whole chapter explaining everything about signal handling.

您始终在您安装自己的处理程序（请参阅信号联机手册（）或<$ C $得到previously设置信号处理器（函数指针） C>的sigaction（））。

You always get the previously set signal handler (a function pointer) when you install your own handler (see manpages for signal() or sigaction()).

previous_handler = signal(SIGINT, myhandler);

一般的规则是，你总是可以（）再次将信号重置为previous处理程序和加薪。

The general rule is, that you can always reset to the previous handler and raise() the signal again.

void myhandler(int sig) {
  /* own stuff .. */
  signal(sig, previous_handler);
  raise(sig);
  /* when it returns here .. set our signal handler again */
  signal(sig, myhandler);
}

有一个的一般规则的缺点：其分别对应的信号硬件异常通常被分配到某个指令导致异常。所以，当你再次上调的信号，相关的指令是不一样的最初。这可以，但不应该损害其他信号处理程序。

There is one disadvantage of the general rule: Hardware exceptions which are mapped to signals are usually assigned to a certain instruction which caused the exception. So, when you raise a signal again, the associated instruction is not the same as originally. This can but should not harm other signal handlers.

另一个劣势是，每次上调信号导致了大量的处理时间。以prevent过度使用的提高（​​）您可以使用下列选项：

Another disadvantage is, that each raised signal causes a lot of processing time. To prevent excessive use of raise() you can use the following alternatives:

1. 在 SIG_DFL 函数指针指向的情况下，解决 0 （这显然是不合法的地址）。因此，您必须再次信号复位处理程序和加薪（）。

1. In case of SIG_DFL the function pointer points to address 0 (which is obviously no valid address). Thus, you have to reset the handler and raise() the signal again.

if (previous_handler == SIG_DFL)
{
  signal(sig, SIG_DFL);
  raise(sig);
  signal(sig, myhandler);
} 

SIG_IGN 的价值 1 （也无效地址）。在这里，你可以返回（什么都不做）。

SIG_IGN has value 1 (also an invalid address). Here you can just return (do nothing).

else if (previous_handler == SIG_IGN)
{
  return;
} 

否则（既不 SIG_IGN 也不 SIG_DFL ）你收到一个有效的函数指针和您能直接调用句柄，

Otherwise (neither SIG_IGN nor SIG_DFL) you have received a valid function pointer and you can call the handler directly,

else
{
  previous_handler(sig);
}

当然，你必须要考虑不同的API，以及（见信号联机手册（）和的sigaction（））。

Of course, you have to consider the different APIs as well (see manpages for signal() and sigaction()).

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