istream 在 while-switch 循环中崩溃

Question

我在 while 循环中有一个开关。在我三次调用选项 4 之后，程序在下次我输入决定在 switch 中进入哪种情况的 int 时崩溃。我不知道为什么会这样。 这是while循环的代码：

void Menu::start()
{
    Store st;
    int op=1,num,quantity;
    string name;
    while(op!=0)
    {
        cin>>op;
        try
        {
            switch(op)
            {
                    case 1:
            {
                cin>>num>>name;
                st.addProduct(num,name);
                break;
            }
            case 4:
                {
                    cin>>num>>quantity;
                    st.sellProduct(num,quantity);
                    break;
                }
            case 0:
                break;
            default:
                throw(exception("Unknown option, try again.\n"));
            } //end of switch
        } //end of try
//catches
    } //end of while
}

/*****************************************************************************
* function name: addProduct
* The Input: This Store, const& int num, const& string name
* The output: If product with given num doesn't exist in store, adds it to
* store.
* The Function operation: uses the products map.
*****************************************************************************/
void Store::addProduct( const int& num,const string& name )
{
    //if product doesn't exist in map, add it
    if(prods.find(num)==prods.end())
        prods.insert(pair<int,Product>(num,Product(num,name)));
    //otherwise issue an error
    else
        throw(AddProdException(num));
}

/*****************************************************************************
* function name: sellProduct
* The Input: This Store, const int& prodNum, const unsigned int& quantityBought
* The output: If product doesn't exist or quantityBought is more than 10 units
* more than quantity in stock, issues an error. Otherwise, sells the product
* and if needed, issues a shipment such that after the purchase the store will
* be left with 20 units.
* The Function operation: uses the products and orders map.
*****************************************************************************/
void Store::sellProduct( const int& prodNum, const unsigned int& quantityBought )
{
    if(prods.find(prodNum)!=prods.end())
    {
        Product& pr = prods.find(prodNum)->second;
        const int& signedQB=quantityBought, signedPQ=pr.getQuantity();
        if( signedPQ<signedQB-10 )
            //store can't supply product
            throw(BuyQuanException(prodNum,quantityBought));
        //make purchase
        else
        {
            //purchase only what left in stock
            if(signedPQ<signedQB )
            {
                //issue shipment
                Order order=Order(prodNum,20+quantityBought-pr.getQuantity());
                orders.insert(pair<int,Order>(order.getID(),order));
                //document order
                purchaseDocs.add(new Documentation(pr,quantityBought,
                    orders.find(order.getID())->second));
                //buy product
                pr.decreaseQuantity( pr.getQuantity() );
            }
            //purchase requested amount
            else
            {
                //buy product
                pr.decreaseQuantity( quantityBought );
                //document order
                purchaseDocs.add(new Documentation(pr,quantityBought));
            }
        } //else regarding making the purchase

    } //if regarding found the product
    //otherwise issue an error
    else
        throw(BuyProdException(prodNum));
}

3 次进入 case 4 后，（并且仅在 case 4 中，仅在 3 次后），它在下一次到达 cin>>op 时崩溃，在 istream 文件中。崩溃是指弹出以下错误消息：“Ex6.exe 中 0x4a34870c 处的未处理异常：0xC0000005：访问冲突。”欢迎帮助！

Answer 1

这个：

const char* errStr=e.what();
cout<<errStr;
//errStr is a dynamically allocated string we don't need anymore <-----------
delete[] errStr;

这是一个糟糕的假设。 std::exception::what 返回的 const char* 不是动态分配的，它只是一个指向异常内部分配的字符串的指针。您不得删除该指针。您的代码中可能还有其他一些错误，但您应该修复它。