c++ - C++无效的读取大小4 valgrind

由于某种原因，我收到“读取大小4无效”错误，我无法弄清楚。我在网上搜索了答案，但这对我的代码没有帮助。总结我的代码的作用，它是一个库存交易模拟器。将显示给用户选项，然后他们可以选择自己想做的事情。目前，我在“出售股票”时遇到问题。这是它的样子。

Stock* newStock = new Stock();
view->getStockData(newStock);

Stock* s = stocks->findElement(newStock);

if(s->getAOS()-newStock->getAOS() > 0) { // There is still some shares remaining
    // Haven't done this yet

} else if (s->getAOS()-newStock->getAOS() == 0) { // There is no shares remaining
        double result = s->calculate(newStock->getPrice(), s->getPrice(), s->getAOS());
        view->printResults(result, 0);

        stocks->remove(newStock);

} else { // Resulted with a negative value
    // Haven't done this yet
}

查看-> getStockData(newStock);看起来像这样:

void UImanager::getStockData(Stock* stock) {
    // Initializing all the stock data
    string    str = "";
    string    symbol, companyName;
    double    price;
    int       amountOfShares;

    cout << endl << "Enter the stock's symbol (e.g. AAPL):  ";
    getline(cin, symbol);

    cout << endl << "Enter the companies name:   ";
    getline(cin, companyName);

    cout << endl << "Enter the price of the stock:   ";
    getline(cin, str);
    stringstream ss(str);
    ss >> price;
    str = "";

    cout << endl << "Enter the amount of shares:    ";
    getline(cin, str);
    stringstream ss1(str);
    ss1 >> amountOfShares;
    str = "";

    Stock* tmpStock = new Stock(symbol, companyName, price, amountOfShares);
    *stock = *tmpStock;
    delete tmpStock;
}

股票类如下所示:

Stock::Stock(string s, string c, double p, int aOS) {
    symbol = s;
    companyName = c;
    price = p;
    amountOfShares = aOS;
    fee = 10;
}

string Stock::getSymbol()      { return symbol; }
string Stock::getCompanyName() { return companyName; }
double Stock::getPrice()       { return price; }
int    Stock::getAOS()         { return amountOfShares; }
int    Stock::getFee()         { return fee; }

bool Stock::operator==(Stock& s) {
    if (this->getSymbol() == s.getSymbol()) {
        return true;
    }

    return false;
}

// More below this, but that code doesn't matter for this problem

我将股票存储在我制作的模板化Dlist中。这是findElement(T *):

template <class T>
T* Dlist<T>::findElement(T* item) {
    Node<T>* currNode = head;

    while (currNode != 0) { // iterate through the Dlist
        if (currNode->data == item) { // uses the operator overloaded == from Stock
            return currNode->data;
        }

        currNode = currNode->next;
    }

    // gets to this point if nothing was found
    return 0;
}

这就是valgrind所说的:

==2459== Invalid read of size 4
==2459==    at 0x804A4EC: Stock::getAOS() (in /home/student/Desktop/Stock Paper Trading/spt)
==2459==    by 0x8049356: SPTcontrol::launch() (in /home/student/Desktop/Stock Paper Trading/spt)
==2459==    by 0x8048F8D: main (in /home/student/Desktop/Stock Paper Trading/spt)
==2459==  Address 0x10 is not stack'd, malloc'd or (recently) free'd
==2459==
==2459==
==2459== Process terminating with default action of signal 11 (SIGSEGV)
==2459==  Access not within mapped region at address 0x10
==2459==    at 0x804A4EC: Stock::getAOS() (in /home/student/Desktop/Stock Paper Trading/spt)
==2459==    by 0x8049356: SPTcontrol::launch() (in /home/student/Desktop/Stock Paper Trading/spt)
==2459==    by 0x8048F8D: main (in /home/student/Desktop/Stock Paper Trading/spt)

因此，我了解到这是在告诉我在Dlist中找到我的股票类信息后出现问题，但是我真的不明白为什么或如何解决它？任何帮助将不胜感激。谢谢。

最佳答案

在我看来，s是空指针，因为Dlist::findElement返回空指针。

最大的线索是valgrind抱怨的地址。您是否看到它说“地址0x10没有被堆栈，malloc或最近释放”？真正的地址如此接近零是非常不寻常的(读:几乎完全闻所未闻)。这几乎总是意味着您的代码遇到一个空指针，该指针在大多数系统上恰好由零地址表示，然后对其进行了一些算术运算(例如，如果Stock位于地址0，那么其amountOfShares在哪里？？在地址16 = 0x10，也许)。

您可以通过添加一些显式检查空指针的代码，或在调试器中运行代码并逐步调试来检查此问题。

如果我的猜想是正确的(或者是错误的，但某些类似的猜想是正确的)，这就是为什么要从Dlist::findElement获取空指针。但我会让你自己解决这个问题。

关于c++ - C++无效的读取大小4 valgrind，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/36553112/