c++ - 字符串超出范围异常

Question

我试图理解字符串中的 out_of_range 异常

#include<iostream>
#include<exception>
using namespace std;

int main()
{
    try{
        string str = "Hello";
        str.at(100);//throws exception and get caught
        //str[100]; //this is a run time error, program crashes
    }
    catch (out_of_range &e)
    {
        cout << e.what() << endl;
    }

}

为什么数组访问字符串不会抛出任何异常和崩溃，而 .at 工作正常？

开发环境:VS2013

Answer 1

这是因为 [] 运算符不检查任何内容，而 at() 会检查任何内容。 CppReference 说:

std::basic_string::at

Returns a reference to the character at specified location pos. Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.

std::basic_string::operator[]

Returns a reference to the character at specified location pos. No bounds checking is performed.