为什么我的信号处理程序（它抛出异常）不会触发多次？ [英] Why doesn't my signal handler (which throws an exception) trigger more than once?

问题描述

我尝试使用sigaction设置异常处理程序。它适用于第一个异常。但是在第一个异常之后不调用sigaction处理程序，当第二个信号发生时程序突然结束。

I am trying to set up an exception handler using sigaction. It works well for the first exception. But the sigaction handler is not called after the 1st exception and the program ends abruptly when the second signal happens.

#include <iostream>
#include <signal.h>
#include <exception>
#include <string.h>

typedef void (*SigactionHandlerPointer)(int iSignal, siginfo_t * psSiginfo, void * psContext);

using namespace std;

void SigactionHookHandler( int iSignal, siginfo_t * psSiginfo, void * psContext )
{
   cout << "Signal Handler Exception Caught: std::exception -- signal : " << iSignal << " from SigactionHookHandler()" << endl;

   throw std::exception();
}

class A
{
public:
   A() {}
   virtual ~A() {}

   virtual void fnct1();
   virtual void fnct2() { fnct3(); }
   virtual void fnct3() { fnct4(); }
   virtual void fnct4();
};

void
A::fnct1()
{
   try {
      fnct2();
   }
   catch( std::exception &ex ) {
      cerr << "Signal Handler Exception Caught" << endl;
   }
   catch (...)
   {
      cerr << "Unknow Exception Caught: " << endl;
   }
}

void
A::fnct4()
{
   *(int *) 0 = 0;  // Access violation
}

int main()
{
   struct sigaction oNewSigAction;
   struct sigaction oOldSigAction;

   memset(&oNewSigAction, 0, sizeof oNewSigAction);

   oNewSigAction.sa_sigaction = SigactionHookHandler;
   oNewSigAction.sa_flags     = SA_SIGINFO;

   int iResult = sigaction( SIGSEGV, &oNewSigAction, &oOldSigAction );

   cout << "sigaction installed handler with status " << iResult << endl;

   A * pA = new A();

   cout << "Next message expected is : <<Signal Handler Exception Caught: std::exception>> to pass this test" << endl;
   pA->fnct1();

   // Second exception will never be call the sigaction handler.
   cout << "Next message expected is : <<Signal Handler Exception Caught: std::exception>> to pass this test" << endl;
   pA->fnct1();

   return 0;
}

推荐答案

对彼此。你使用的是什么（抛出异步信号处理程序的异常）只能在几个支持它的编译器之间移植，比如GCC和Intel C / C ++， -fnon-call-exceptions 。

Signals and exceptions are not related to each other. What you're using (throwing exceptions from async signal handlers) is only portable between the few compilers that support it, such as GCC and Intel C/C++ with -fnon-call-exceptions.

也就是说，你忘记做的是取消阻塞信号：当信号处理程序执行时，相同信号的传递被阻止，当信号处理程序通过异常退出时不会被解除阻塞。更改信号处理程序如下：

That said, what you forgot to do is unblock the signal: when a signal handler is executing, the delivery of the same signal is blocked, and it does not become unblocked when the signal handler is exited through an exception. Change the signal handler as follows:

void SigactionHookHandler( int iSignal, siginfo_t * psSiginfo, void * psContext
{
   cout << "Signal Handler Exception Caught: std::exception -- signal : " << iSignal << " from SigactionHookHandler()" << endl;

   sigset_t x;
   sigemptyset (&x);
   sigaddset(&x, SIGSEGV);
   sigprocmask(SIG_UNBLOCK, &x, NULL);

   throw std::exception();
}

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