動態分配的數組作爲C++中的結構成員的分割錯誤？

Question

我正在寫一個程序，使用結構數組來存儲一定數量的學生的姓名，身份證號碼和一系列測試分數。結構數組和測試成績數組成員都需要動態分配。我已經完成了允許用戶爲每個學生輸入測試分數的功能，但是我在最後一個函數（getScores函數）中遇到了cin問題。當使用Linux時，我得到了一個分段錯誤，所以我假設它與動態分配的測試數組是相關的，我只是看不到它。我想知道如何去調試它，並解釋爲什麼會發生這種情況，所以我可以在將來避免它。

//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

一個錯誤是您訪問已刪除對象studentFiles的成員。扭轉線來修復：

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

理想情況下，使用std::vector<>代替動態分配和釋放手動存儲器。

另請注意，代碼只初始化數組第一個成員的Student::tests，其餘的Student對象具有未初始化的此成員。表達式studentFiles[i].tests[j]的結果未定義，並可能導致崩潰。

您需要初始化每個Student的Student::tests成員。完成後，取消分配每個Student的Student::tests。