无法获得每个学生的姓名和年龄。相反，我得到了奇怪的字符和年龄 = 0？答案

【问题标题】：Can't get the name and age of each student. Instead I get weird characters and age = 0?无法获得每个学生的姓名和年龄。相反，我得到了奇怪的字符和年龄 = 0？
【发布时间】：2021-12-08 18:21:21
【问题描述】：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct Student {
    char name[50];
    int age;
} student;


int main() {
    char name[50];
    int age;

    // Requirement values
    char stop[] = "stop";
    int check = 1;

    int countOfStudents = 0;

    // Array with students
    student* students = malloc(countOfStudents);

    while(check) {

        scanf("%s", &name);

        if(!strcmp(name, stop) == 0) {

            scanf(" %i", &age);
            struct Student student = {*name, age};

            strcpy(students[countOfStudents].name, student.name);
            students[countOfStudents].age = student.age;

            countOfStudents++;
        } else {
            printf("You wrote stop \n");
            check = 0;
        }
    }

    for (int i = 0; i < countOfStudents; ++i) {
        printf("Name = %s , Age = %i", students[i].name, students[i].age);
        printf("\n");
    }

    return 0;
}

我有一个学生数组。每个学生都是一个结构，并且有一个名字和年龄。我必须注册每个学生，直到用户写“停止”。

输入：

test
12
stop

输出是这样的：

You wrote stop
ogram Files (x86)
Name = t♀ , Age = 0

为什么会这样？

【问题讨论】：

嗯，我想知道these errors是什么意思。
也相关：ericlippert.com/2014/03/05/how-to-debug-small-programs
@SuperStormer 我现在编辑了代码，没有任何警告。我仍然没有得到正确的输出？ :O
student* students = malloc(countOfStudents);。在此行之前尝试printf("countOfStudents: %d\n", countOfStudents);。 :) 。 + 其他一些人。
SuleymanSelcuk，您认为struct Student student = {{*name, age}}; 会做什么？注意*name 是一个char。

标签： arrays c input struct output

【解决方案1】：

至少这个问题

分配错误

int countOfStudents = 0;
student* students = malloc(countOfStudents);

分配零内存。

试试

int countOfStudents = 0;
int Students_MAX = 100;
student* students = malloc(sizeof *students * Students_MAX);

并限制迭代：

while(countOfStudents < Students_MAX && check)

最好使用宽度限制

char name[50];
...
// scanf("%s", name);
scanf("%49s", name);

struct Student student = {{*name, age}}; 不是必需的初始化。

【讨论】：

【解决方案2】：

内存分配错误。以下代码将起作用。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct Student
{
    char name[50];
    int age;
} student;

int main()
{
    char name[50];
    int age;

    char stop[] = "stop";
    int check = 1;

    int countOfStudents = 0;

    student* students = NULL;

    while(check)
    {
        scanf("%49s", name); // 49 + '\0' = 50
        if(!strcmp(name, stop) == 0)
        {
            scanf(" %i", &age);
            if(!students)
            {
                students = (student*) malloc(sizeof(student*)); // allocating for the first
            }
            else
            {
                students = (student*) realloc(students, sizeof(student*)); // allocating 
            }
            strcpy(students[countOfStudents].name, name);
            students[countOfStudents].age = age;
            countOfStudents++;
         }
         else
         {
            printf("You wrote stop \n");
            check = 0;
         }
     }

    for (int i = 0; i < countOfStudents; ++i) 
    {
        printf("Name = %s , Age = %i", students[i].name, students[i].age);
        printf("\n");
    }

    free(students);
    students = NULL;

    return 0;
}

【讨论】：

sizeof(student*) 是指针的大小。建议sizeof *students.
realloc(students, sizeof(student*)) --> 需要按countOfStudents+1扩展。