C++异常

#include <stdio.h>
 
// 定义错误码
enum ErrorCode {
    ERR_SUCCESS = 0,
    ERR_FAILURE = 1,
    ERR_INVALID_ARG = 2
};
 
// 示例函数，可能会失败
int mightFailFunction(int value) {
    // 检查参数是否有效
    if (value <= 0) {
        return ERR_INVALID_ARG; // 如果参数无效，返回对应的错误码
    }
    
    // 模拟一些可能失败的操作
    if (rand() % 2 == 0) { // 假设随机决定成功与否
        return ERR_SUCCESS; // 成功时返回0
    } else {
        return ERR_FAILURE; // 失败时返回非零错误码
    }
}
 
int main() {
    int result = mightFailFunction(-1);
    if (result == ERR_SUCCESS) {
        printf("操作成功\n");
    } else if (result == ERR_FAILURE) {
        printf("操作失败\n");
    } else if (result == ERR_INVALID_ARG) {
        printf("参数无效\n");
    } else {
        printf("未知错误码: %d\n", result);
    }
    
    return 0;
}

double Division(int a, int b)
{
	//当p=0时抛出异常
	if (b == 0)
	{
		throw"Division by zero condition!";
	}
	else
	{
		return ((double)a / (double)b);
	}
}

int main()
{
	try
	{
        int a,b;
        cin>>a>>b;
		Division(a,b);
	}
	catch(const char* errmsg)
	{
		cout << errmsg << endl;
	}
	return 0;
}

double Division(int a, int b)
{
	//当p=0时抛出异常
	if (b == 0)
	{
		throw"Division by zero condition!";
	}
	else
	{
		return ((double)a / (double)b);
	}
}
void fxx()
{
	int i = 0;
	cin >> i;
	if (i % 2 == 0)
	{
		throw 1;
	}
}
void func()
{
	try
	{
		fxx();
	}
	catch (int  x)
	{
		cout <<__LINE__<< "捕获异常" << x << endl;//__LINE__代表当前行号
	}

	cout << "===============" << endl;
}

int main()
{
	try
	{
		func();
	}
	catch(const char* errmsg)
	{
		cout << errmsg << endl;
	}
	catch (int x)
	{
		cout << __LINE__ << x << endl;
	}
	cout << "++++++++++++++++++++++" << endl;
	return 0;
}

double Division(int a, int b)
{
	// 当b == 0时抛出异常
	if (b == 0)
	{
		throw "Division by zero condition!";
	}
	return (double)a / (double)b;
}

void fyy() noexcept
{
	int len, time;
	cin >> len >> time;
	cout << Division(len, time) << endl;
}

void func()
{
	//这里可以看到如果发生除0错误抛出异常，下面的array数组就没有得到释放
	//所以这里捕获异常但是不处理异常，异常还是交给外面处理，这里捕获了再抛出去
	//就能delete array了
	int* array = new int[10];
	try
	{
		fyy();
	}
	catch (...)
	{
		//捕获异常不是为了处理异常
		//是为了释放内存，然后异常再重新抛出
		cout << "delete[]" << array << endl;
		delete[] array;
		throw;//捕到什么抛什么
	}
	cout << "delete[]" << array << endl;
	delete[] array;
}

// 这里表示这个函数会抛出A/B/C/D中的某种类型的异常

void fun() throw(A，B，C，D);

// 这里表示这个函数只会抛出bad_alloc的异常

void* operator new (size_t size) throw (bad_alloc);

// 这里表示这个函数不会抛出异常

void* operator delete (size_t size, void* ptr) throw();

// C++11 中新增的noexcept，表示不会抛异常

thread() noexcept;

thread (thread&& x) noexcept;

class Exception
{
public:
	Exception(const string& errmsg, int id)
		:_errmsg(errmsg)
		, _id(id)
	{}

	virtual string what() const
	{
		return _errmsg;
	}

protected:
	string _errmsg;  // 错误描述
	int _id;         // 错误编号
};

// 继承和多态
class SqlException : public Exception
{
public:
	SqlException(const string& errmsg, int id, const string& sql)
		:Exception(errmsg, id)
		, _sql(sql)
	{}

	virtual string what() const
	{
		string str = "SqlException:";
		str += _errmsg;
		str += "->";
		str += _sql;
		return str;
	}
private:
	const string _sql;
};

class CacheException : public Exception
{
public:
	CacheException(const string& errmsg, int id)
		:Exception(errmsg, id)
	{}

	virtual string what() const
	{
		string str = "CacheException:";
		str += _errmsg;
		return str;
	}
};

class HttpServerException : public Exception
{
public:
	HttpServerException(const string& errmsg, int id, const string& type)
		:Exception(errmsg, id)
		, _type(type)
	{}

	virtual string what() const
	{
		string str = "HttpServerException:";
		str += _type;
		str += ":";
		str += _errmsg;
		return str;
	}
private:
	const string _type;
};
class A
{
public:
	A()
	{
		cout << "A()" << endl;
		_ptr1 = new int;
		_ptr2 = new int;
	}
	~A()
	{
		cout << "~A()" << endl;
		delete _ptr1;
		delete _ptr2;
	}
private:
	int* _ptr1;
	int* _ptr2;
};
void SQLMgr()
{
	srand(time(0));
	if (rand() % 7 == 0)
	{
		throw SqlException("权限不足", 100, "select * from name = '张三'");
	}

	cout << "!!!!!!!!!!!!!!!!!!!!!!!!运行成功" << endl;
}

void CacheMgr()
{
	srand(time(0));
	if (rand() % 5 == 0)
	{
		throw CacheException("权限不足", 100);
	}
	else if (rand() % 6 == 0)
	{
		throw CacheException("数据不存在", 101);
	}
	SQLMgr();
}

void HttpServer()
{
	A aa;
	srand(time(0));
	if (rand() % 3 == 3)
	{
		throw HttpServerException("请求资源不存在", 100, "get");
	}
	else if (rand() % 4 == 0)
	{
		throw HttpServerException("权限不足", 101, "post");
	}
	CacheMgr();
}

int main()
{
	try {
		vector<int> v(10, 5);
		// 这里如果系统内存不够也会抛异常

		v.reserve(1000000000);
		// 这里越界会抛异常

		v.at(10) = 100;
	}
	catch (const exception& e) // 这里捕获父类对象就可以

	{
		cout << e.what() << endl;
	}
	catch (...)
	{
		cout << "Unkown Exception" << endl;
	}
	return 0;
}