为什么我的信号处理程序（引发异常）不会多次触发？

Question

我正在尝试使用 sigaction 设置异常处理程序。它适用于第一个异常。但是 sigaction 处理程序在第一个异常之后没有被调用，并且当第二个信号发生时程序突然结束。

#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;
}

Answer 1

信号和异常彼此不相关。您正在使用的（从异步信号处理程序中抛出异常）只能在支持它的少数编译器之间移植，例如 GCC 和带有-fnon-call-exceptions 的 Intel C/C++。

也就是说，您忘记做的是解除阻塞信号：当信号处理程序正在执行时，相同信号的传递被阻塞，并且当信号处理程序通过异常退出时它不会被解除阻塞。更改信号处理程序如下：

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();
}

Answer 2

标准 C++ 没有提及信号，或者它们如何与异常交互。您正在尝试执行的操作将完全特定于您使用的操作系统平台，并且可能是您编译代码所使用的特定编译器。