在 C 中传递动态结构后无法写入内存

Question

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>
#define FLUSH myFlush()

struct testInfo {
    int grade;
    char letterGrade;
    char student[30];
};

void menuPrint(int);
void enterScores(struct testInfo **scores, int size);
void printScores(struct testInfo scores[], int size);
char getChoice();
void myFlush();

int main(void) {
    struct testInfo *testScores = { 0 };
    char userChoice;
    int size = 0;
    do {
        system("clear");
        menuPrint(1);
        userChoice = getChoice();
        switch (userChoice) {
        case 'e': case 'E':
            system("clear");
            menuPrint(2);
            printf("Please enter the number of test scores: ");
            scanf_s("%d", &size); FLUSH;
            testScores = (struct testInfo*)malloc(size * sizeof(struct testInfo));
            if (!testScores) { //if there is an error in allocating the memory, exits program.
                printf("\nA problem has occured with malloc.");
                exit(EXIT_FAILURE);
            }
            else {
                enterScores(&testScores, size);
            }
            system("pause");
            break;
        case 'p': case 'P':
            printScores(testScores, size);
            system("pause");
            free(testScores);
            break;
        case 'l': case 'L':
            system("pause");
            break;
        }
    } while (userChoice != 'l' && userChoice != 'L');
    return 0;
}//end main

我试图将一个动态结构传递给一个函数，这样用户就可以写下学生的姓名和他们在考试中获得的考试成绩。我使用作为参考来弄清楚如何将动态结构传递给函数，但是当用户开始输入时，我可以在抛出“访问冲突写入”异常之前完成 1 个循环。

void enterScores(struct testInfo **scores, int size) {
    int i;
    char name[30];

    for (i = 0; i < size; i++) {
        printf("\nEnter student's name: ");
        fgets(name, 30, stdin);
        strcpy(scores[i]->student, name);
        printf("\nEnter test score: ");
        scanf_s("%i", &scores[i]->grade);
        while (scores[i]->grade < 0 || scores[i]->grade > 120) {
            printf("\nError in grade range (0-120), try again.");
            printf("\nEnter test score: ");
        }
        //determines letter grade from test Score
        if (scores[i]->grade > 90) {
            scores[i]->letterGrade = 'A';
        }
        if (scores[i]->grade < 90 && scores[i]->grade >= 80) {
            scores[i]->letterGrade = 'B';
        }
        if (scores[i]->grade < 80 && scores[i]->grade >= 70) {
            scores[i]->letterGrade = 'C';
        }
        if (scores[i]->grade < 70 && scores[i]->grade >= 60) {
            scores[i]->letterGrade = 'D';
        }
        if (scores[i]->grade < 60 && scores[i]->grade >= 0) {
            scores[i]->letterGrade = 'F';
        }
    }
}//end enterScores

Answer 1

您当前的 enterScores 正在接受指向 struct testInfo 的指针数组，但实际传递的是指向 struct testInfo 的单个指针的指针。这被视为 one-element 数组，因此访问 scores[1] 和进一步无效。

你想要的似乎是：

函数声明：

void enterScores(struct testInfo scores[], int size);

（使用与printScores相同的方案）

调用函数：

                enterScores(testScores, size);

（删除&）

函数定义：

void enterScores(struct testInfo scores[], int size) {
    int i;
    char name[30];

    for (i = 0; i < size; i++) {
        printf("\nEnter student's name: ");
        fgets(name, 30, stdin);
        strcpy(scores[i].student, name);
        printf("\nEnter test score: ");
        scanf_s("%i", &scores[i].grade);
        while (scores[i].grade < 0 || scores[i].grade > 120) {
            printf("\nError in grade range (0-120), try again.");
            printf("\nEnter test score: ");
        }
        //determines letter grade from test Score
        if (scores[i].grade > 90) {
            scores[i].letterGrade = 'A';
        }
        if (scores[i].grade < 90 && scores[i].grade >= 80) {
            scores[i].letterGrade = 'B';
        }
        if (scores[i].grade < 80 && scores[i].grade >= 70) {
            scores[i].letterGrade = 'C';
        }
        if (scores[i].grade < 70 && scores[i].grade >= 60) {
            scores[i].letterGrade = 'D';
        }
        if (scores[i].grade < 60 && scores[i].grade >= 0) {
            scores[i].letterGrade = 'F';
        }
    }
}//end enterScores

（更改参数并将 -> 替换为 .）

在 C 中传递动态结构后无法写入内存

Unable to write to memory after passing dynamic structure in C

c

dynamic-memory-allocation

dynamic-struct