c++ - 处理异常时抛出异常

Question

我正在阅读“C++ Programming Language 4th edition”一书，对有关异常处理的段落有疑问:

There are cases where exception handling must be abandoned for less subtle error-handling techniques. The guiding principles are:

• Don't throw an exception while handling an exception.
• Don't throw an exception that can't be caught.

If the exception-handling implementation catches you doing either, it will terminate your program.

有人可以给我一个第一种情况的例子吗？我只想到了这样的事情，但根据 g++，它是一个有效的代码:

try
{
    throw 1;
}
catch(...)
{
    try
    {
        throw 2;
    }
    catch(...)
    {
        cout << "OK";
    }
}

Answer 1

这有点误导；可以从异常处理程序中抛出(这是我对“处理异常时”的理解)，只要有另一个处理程序可以捕获它。

问题是，如果您从在堆栈展开期间被销毁的对象的析构函数中抛出异常。那样的话，有两个未处理的异常，通常的异常机制只能处理一个；所以响应是调用 terminate。

例子:

struct dodgy {~dodgy() {throw "Don't do this!";}};

try {
    dodgy d;
    throw 1;
} catch (...) {
    // Never reached: destroying `d` killed the program.
}