打开文件后程序崩溃 [英] Program crashes after opening file

问题描述

我需要从文件中读取值到我的程序。文件已成功打开，但后来立即崩溃。我的代码有问题吗？

I need to read values from a file into my program. The file is opening successfully, but then it crashes right away. Is there something wrong with my code?

void createList(intNode*& intList)
{
    intNode* lastInt; //points to last integer in file
    lastInt = NULL;
    int fileInt; //int read from input file
    ifstream intInputFile;

    intInputFile.open("intInput.txt");
    if (intInputFile.is_open())
    {
        cout << "intInput.txt open successful" << endl;
    }
    else
    {
        cout << "intInput.txt open unsuccessful" << endl;
    }
    intInputFile >> fileInt;
    while(!intInputFile.eof())
    {
        intNode* anotherInt;
        anotherInt = new intNode;
        if(intList==NULL)
        {
            intList = anotherInt;
            lastInt = anotherInt;
        }
        else
        {
            lastInt->nextNode = anotherInt;
        }
        lastInt = lastInt->nextNode;
        lastInt->intValue = fileInt;
        lastInt->nextNode = NULL;
        intInputFile >> fileInt;
    }
    intInputFile.close();
    cout << "List created from input file" << endl;
}

谢谢。

编辑：

检查后，我遇到了问题

else
    {
        lastInt->nextNode = anotherInt;
    }

因此，此代码必须有问题：

So there must be a problem with this code:

    lastInt = lastInt->nextNode;
    lastInt->intValue = fileInt;
    lastInt->nextNode = NULL;
    intInputFile >> fileInt;

因为我之前有一个cout语句，它没有工作。

Because I had a cout statement directly after it and it didn't work.

在进一步研究之后，问题出在这一行：

And after looking into it more, the problem is with this line:

     intInputFile >> fileInt;

推荐答案

假设 intList 不是 NULL ，那么您将在 lastInt-> nextNode = anotherInt; 第一次循环，而 lastInt 仍然是 NULL 导致程序崩溃（由于它遵循一个空指针） 。

Assuming intList isn't NULL, then you'll call lastInt->nextNode = anotherInt; during your first iteration of the loop while lastInt is still NULL causing the program to crash (due to it following a null pointer).

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