C++学习日志48-----异常处理、bad

目录

• 一、异常处理
• 二、bad_alloc异常
• 三、bad_cast异常
• 四、out_of_range异常

---

一、异常处理

#include
using std::cout;
using std::endl;
using std::cin;

int main()
{
	int x{ 0 }, y{ 0 };
	cin >> x >> y;
	try
	{
		if (y == 0) throw y;
		cout << x / y;
	}
	catch (int& e)
	{
		cout << "the second number is :" << e << endl;
	}


}

结果如上图所示。

二、bad_alloc异常

#include
#include
#include
#include

using std::cout;
using std::endl;

int main()
{
	try
	{
		for (int i = 0; i < 10000; i++)
		{
			auto* p = new long long int[700000];
			cout << i << " array" << endl;
		}
	}
	catch (std::bad_alloc& e)
	{
		cout << " exception:  " << e.what() << endl;
	}


}

结果如上图所示

三、bad_cast异常

#include
#include
#include
using std::cout;
using std::endl;
class Student
{
public:
	Student() = default;
	virtual void foo() {};
};
class Undergraduate :public Student {};
class Graduate : public Student{};

int main()
{
	Undergraduate u;
	Graduate g;
	Student* s1 = &u;
	Student* s2 = &g;
	Graduate* p = dynamic_cast<Graduate *>(s2);
	long x = reinterpret_cast<long>(p);
	cout << x << endl;
	Graduate* p2 = dynamic_cast<Graduate*>(s1);
	if (p2 == nullptr)
	{
		cout << "cast s1 to Graduate failed" << endl;
	}
	else
	{
		cout << " cast s1 to Graduate * succeeded" << endl;
	}
	try{
	Graduate& r1 = dynamic_cast<Graduate&>(u);
	}
	catch (std::bad_cast& e)
	{
		cout << "Exception " << e.what() << endl;
	}
}

结果如上图所示。

四、out_of_range异常

#include
#include
using std::cout;
using std::endl;


int main()
{
	std::vector v{ 'a','b','c','d','e' };
	try
	{
		for (int i = 0; i <= 5; i++)
		{
			//  cout << v[i];  i=5越界
			cout << v.at(i) << endl; //i=会抛出异常
		}
	}
	catch (std::out_of_range& e)
	{
		cout << "Exception: " << e.what() << endl;
	}

}

---

结果如上图所示。