Question

addStudent函数和mainMenu函数是重要的两个函数。

#include <iostream>
#include <string>

using namespace std;

struct Student
{
   string name;
   string major;
   Student *p_next;
};

Student *addStudent(Student *p_students)
{
   Student *p_new_student = new Student;
   cout << "Student name: \n";
   cin >> p_new_student->name;
   cout << p_new_student->name << "'s major: \n";
   cin >> p_new_student->major;

   Student *p_place_holder = new Student;
   Student *p_all_students = new Student;
   p_all_students = p_students;
   p_place_holder = NULL;

   if (p_students == NULL) // Adds the first element to the linked list which was initialized to NULL
   {
      p_new_student->p_next = p_students;
      delete p_place_holder;
      delete p_all_students;
      return p_new_student;
   }

   else // Adds elements beyond the first element to the linked list
   {
      while (p_all_students != NULL)
      {
         if (p_new_student->name.compare(p_all_students->name) <= 0)
         {
            if (p_place_holder == NULL) /* if p_new_student->name is before
            p_all_students->name and p_all_students is still the first element in the list*/
            {
               p_new_student->p_next = p_all_students;
               p_all_students = p_new_student;
               delete p_place_holder;
               return p_all_students;
            }

            else
            {
               p_new_student->p_next = p_all_students;
               p_place_holder->p_next = p_new_student;
               return p_students;
            }

         }

         else if (p_new_student->name.compare(p_all_students->name) > 0)
         {
            p_place_holder = p_all_students;
            p_all_students = p_all_students->p_next;
         }
      }
   }
}

void mainMenu(Student *p_students)
{
   int response = 0;
   cout << "1. Add Student\n";
   cout << "2. View Students\n";
   cin >> response;

   if (response == 1) // calls addStudent 4 times and then mainMenu
   {
      p_students = addStudent(p_students);
      p_students = addStudent(p_students);
      p_students = addStudent(p_students);
      p_students = addStudent(p_students);
      mainMenu(p_students);
   }

   else if (response == 2) // lists the students and their majors and then exits
   {
      while (p_students != NULL)
      {
         cout << p_students->name << '\n';
         cout << p_students->major << "\n\n";
         p_students = p_students->p_next;
      }
   }

   delete p_students; // hopefully deletes all allocated memory
}

int main()
{
   Student *p_students = new Student;
   p_students = NULL;

   mainMenu(p_students);
}

基本上想知道“删除p_students;”在mainMenu函数中将正确删除所有已分配的内存，以便程序不会泄漏内存。感谢任何帮助，非常感谢。

Answer 1

这些行会泄漏Student的实例：

Student *p_place_holder = new Student;
Student *p_all_students = new Student;
p_all_students = p_students;
p_place_holder = NULL;

您分配学生，将其分配给p_place_holder，然后稍后用NULL覆盖指针而不删除实例。

您还有：

p_students = addStudent(p_students);
p_students = addStudent(p_students);
p_students = addStudent(p_students);
p_students = addStudent(p_students);

将覆盖p_students三次而不试图释放旧值中的内存。

更大的问题是你以delete p_students结束，但是这不会检查Student结构以查找其中的指针，删除它等，递归地，正如您所希望的那样。您几乎泄漏了所有已分配的内存。

我认为你误解了新的和删除对的结合。

Answer 2

您必须使用强制所有权指针来避免内存泄漏 - 例如，unique_ptr和shared_ptr。您永远无法使用delete来有效防止泄密。

这会泄漏内存吗？

2 个答案: