动态分配的数组作为c ++中结构的成员的分段错误？

Question

我正在编写一个程序，它使用一个结构数组来存储一定数量学生的姓名、身份证号和一组考试成绩。结构数组和测试分数成员数组都需要动态分配。我已经开始使用允许用户输入每个学生的考试成绩的功能，但是我在最后一个函数（getScores 函数）中遇到了 cin 问题。使用 Linux 时出现分段错误，因此我假设它与作为结构成员的动态分配的测试数组有关，我只是看不到它。我想知道如何调试它并解释为什么会发生这种情况，以便将来避免它。

//Preprocessor Directives
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;

//Structure declaration
struct Students
{
    string name; //Student name
    int idNum; //Student ID number
    double *tests; //Pointer to an array of test scores
};

//Function prototypes
Students *getStudents(int &);
double *getTests(int &);
void getInfo(string &, int &, int);
void getScores(double &, string, int);

//Main program section
int main ()
{
    int numStudents = 0;
    int numTests = 0;
    Students *studentFiles = NULL;

    //Call the getStudents function
    studentFiles = getStudents(numStudents);

    //Call the getTests function
    studentFiles->tests = getTests(numTests);

    for(int i = 0; i < numStudents; i++)
    {
        //Call the getInfo function
        getInfo(studentFiles[i].name, studentFiles[i].idNum, i+1);
    }

    for(int i = 0; i < numStudents; i++)
    {
        for(int j = 0; j < numTests; j++)
        {
            getScores(studentFiles[i].tests[j], studentFiles[i].name, j);
        }
    }
    delete [] studentFiles;
    delete [] studentFiels->tests;
    return 0;
}

Students *getStudents(int &numStudents)
{
    Students *studentFiles = NULL;

    //Prompt the user for the number of students
    cout<<"Enter the number of students: ";
    cin>>numStudents;
    //Dynamically allocate an array of structs, one for each student
    studentFiles = new Students[numStudents];

    return studentFiles;
}

double *getTests(int &numTests)
{
    double *tests = NULL;

    //Prompt the user for the number of tests
    cout<<"Enter the number of tests: ";
    cin>>numTests;
    cin.ignore();
    //Dynamicall allocate an array of integers, one for each test 
    tests = new double[numTests];

    return tests;
}

void getInfo(string &name, int &idNum, int index)
{
    //Prompt for each student's name and id number
    cout<<"Enter the name of student #"<<index<<": ";
    getline(cin, name);
    cout<<"Enter the id number of student #"<<index<<": ";
    cin>>idNum;
    cin.ignore();
}

void getScores(double &test, string name, int numTest)
{
    cout<<name<<endl;
    cout<<numTest<<endl;
    //Prompt for each test score for each student
    cout<<"Enter "<<name<<"'s score for test #"<<numTest+1<<": ";
    cin>>test;
}

Answer 1

一个错误是您访问了已删除对象studentFiles 的成员。反转行来解决这个问题：

delete [] studentFiles->tests;    
delete [] studentFiles;

理想情况下，使用std::vector<> 而不是手动动态分配和释放内存。

另请注意，代码仅初始化数组第一个成员的Student::tests，其余Student 对象的此成员未初始化。表达式studentFiles[i].tests[j] 的结果是未定义的，可能会导致崩溃。

您需要初始化每个Student 的Student::tests 成员。完成后，释放每个Student 中的Student::tests。