是否“尝试捕获"?捕获运行时错误(尤其是超出范围的错误) [英] Does "try-catch" catches run time error (especially Out of Range error)

问题描述

在以下示例之一中，我正在遵循使用C ++编程原理和实践中的示例代码，该示例显示了此代码段

I'm following an example code from Programming Principles and Practice Using C++ in one of the example for exception it shows this snippet of code

int main()
{
    try {
        vector<int> v; // a vector of ints
        for (int x; cin >> x; )
            v.push_back(x); // set values
        for (int i = 0; i <= v.size(); ++i) // print values
            cout << "v[" << i << "] == " << v[i] << '\n';
    }
    catch (const out_of_range& e) {
        cerr << "Oops! Range error\n";
        return 1;
    }
    catch (...) { // catch all other exceptions
        cerr << "Exception: something went wrong\n";
        return 2;
    }
}

据我了解，应该捕获到 out_of_range 错误并输出"糟糕！范围错误" .但是，Visual Studio 2019却显示了这一点.

From what I understand it is suppose to catch out_of_range error and output "Oops! Range error". However, the Visual Studio 2019 shows this instead.

有人可以解释为什么它向我展示

can someone explain why it shows me this

推荐答案

"try-catch"是否捕获运行时错误(尤其是超出范围的错误)?

Does "try-catch" catches run time error (especially Out of Range error)?

否，在C ++中，大多数运行时错误都导致未定义行为，而不是异常.仅可以捕获明确引发异常的错误.

No, in C++ most run time errors lead to Undefined Behavior, not exceptions. Only errors which explicitly throw exceptions can be caught.

std :: vector< T> :: operator [] 未指定在您越界访问时抛出异常，这只是未定义的行为，任何事情都可能发生.它甚至似乎可以正常工作.当我在这里尝试时，没有任何可见的错误: https://godbolt.org/z/Pcv9Gn8M9

std::vector<T>::operator[] does not specify that it throws an exception when you access out of bounds, it is just Undefined Behavior and anything can happen. It can even appear to work. When I try it here, there isn't any visible error : https://godbolt.org/z/Pcv9Gn8M9

如果您希望访问范围外的异常，则 std :: vector< T> :: at()会抛出 std :: out_of_range .

If you want an exception on out of bounds access, std::vector<T>::at() does throw std::out_of_range.

为了进行测试，您应该使用 v.at(i)而不是 v [i] .在这里尝试: https://godbolt.org/z/szKxhjxhx .

For your test you should use v.at(i) instead of v[i]. Try it here : https://godbolt.org/z/szKxhjxhx.

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