为什么要通过基类抛出派生类捕获？

对于下面的代码，结果是“EA Exception Finished”，这意味着虽然我们向派生类抛出异常，但它被基类捕获。总是这样吗？如果是这样，我怎样才能让派生类捕获，从而出现“EB Exception Finished”？

我也无法完全理解它是什么意思throw EB() and catch(EA&)。并且确实catch(EA&)表示 catch 块获取 EA 的引用object?

抱歉我的无知。如果您向我推荐一本关于异常结构的书或其他参考资料，那将会有很大的帮助。

class EA {};
class EB: public EA {};

void F()
{
  throw EB();  // throw at EB().
}

int main()
{
  try
  {
    F();
  }
  catch(EA&) // caught here??
  {
    std::cout<<"EA Exception";
  }
  catch(EB&) // why not me? every time?
  {
    std::cout<<"EB Exception";
  }

  std::cout<<" Finished"<<std::endl;

  return 0;
}

改变顺序catch块来修复该行为：

#include <iostream>

class EA {};
class EB: public EA {};

void F()
{
  throw EB();  // throw at EB().
}

int main()
{
  try
  {
    F();
  }
  catch(EB&) // why not me? every time?
  {
    std::cout<<"EB Exception";
  }
  catch(EA&) // caught here??
  {
    std::cout<<"EA Exception";
  }

  std::cout<<" Finished"<<std::endl;

  return 0;
}

编译器甚至会警告您：

main.cpp:21:3: warning: exception of type 'EB' will be caught
   catch(EB&) // why not me? every time?
   ^~~~~
main.cpp:17:3: warning:    by earlier handler for 'EA'
   catch(EA&) // caught here??
   ^~~~~