所以我有这个作业，在那里我有一个叫做Song的结构。通过这个结构，我可以使用Song结构对数组进行动态分配。
因此，当我尝试向结构中的数组添加另一首歌曲时遇到了这个问题。
当使用案例4将另一首歌曲添加到数组时，它将struct Song中变量的值更改为垃圾值。我不知道为什么要这么做。预期的结果应该是阵列扩展并将歌曲添加到aSong。
使用情况4之后，打印aSong数组是问题开始的地方。
我没有编译器错误。该程序只打印出垃圾值。
这是代码（我知道我可以通过将代码放入函数中使其看起来更好）：
#pragma warning(disable : 4996)
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "lab3.h"
//Global variables
struct Song *aSong;
int howMany = 0;
int menu(struct Song *songs) {
int answer = 0;
printf("Choose from the menu: \n");
printf("1. Song menu.\n");
printf("2. Exit\n");
scanf("%d", &answer);
switch (answer)
{
case 1:
printf("Choose from the menu: \n");
printf("1. Add song. \n");
printf("2. Randomize list.\n");
printf("3. Print list.\n");
printf("4. Add another song.\n");
printf("5. Go back\n");
scanf("%d", &answer);
switch (answer)
{
case 1:
printf("How many songs would you like to add right now?: \n");
scanf("%d", &howMany);
getchar();
aSong = (struct Song *) malloc((sizeof(struct Song) * howMany));
for (int i = 0; i < howMany; i++) {
//Adds songs to the array. Depends on how many the user wants to add
printf("Enter a songname: \n");
fgets(aSong[i].titel, SIZE, stdin);
fflush(stdin);
getchar();
printf("Enter the artist/band: \n");
fgets(aSong[i].artist, SIZE, stdin);
fflush(stdin);
getchar();
printf("Enter which year the song was released: \n");
scanf("%d", &aSong[i].releaseD);
fflush(stdin);
getchar();
}
printf("Music added!\n");
getchar();
menu(&songs);
break;
case 3:
printf("-------------------------------\n");
printf("Songs stored: \n");
//Prints the songs
for (int i = 0; i < howMany; i++) {
printf("\nSong titel: %s Band/Artist: %s Release year: %d\n", aSong[i].titel, aSong[i].artist, aSong[i].releaseD);
}
printf("-------------------------------\n");
menu(&songs);
getchar();
break;
case 4:
//Add another song to the array
printf("Add another song: \n");
struct Song* tmp = (struct Song*)malloc((howMany + 1) * sizeof(struct Song));
//Change the array by increasing the nr of slots
for (int i = 0; i < howMany; i++) {
tmp[i] = aSong[i];
}
//Redirect the pointers so it points to the correct array
free(aSong);
aSong = tmp;
tmp = NULL;
printf("Enter song name: \n");
fgets(aSong[howMany].titel, SIZE, stdin);
getchar();
printf("Enter band/artist name: \n");
fgets(aSong[howMany].artist, SIZE, stdin);
getchar();
printf("Enter the year when the song was released:\n");
//scanf(" %d", &aSong[howMany].releaseD);
fgets(aSong[howMany].artist, SIZE, stdin);
getchar();
printf("Song added!");
printf("-------------------");
howMany++;
free(aSong);
menu(&songs);
break;
case 5:
printf("Exit.");
menu(&songs);
break;
}
case 2:
return 0;
break;
}
}
我的main.c文件仅调用menu（＆songs）函数。
我正在使用一个菜单系统，该菜单系统允许用户选择他们想要做的事情。
该系统的基本用法如下：
* You enter the "Add song" menu.
* You choose how many songs you would like to enter
* The user adds the info of the song
* User prints the stored songs with case 3
* User wants to add another song to the array with case 4
* User enters data again to add another song (YOU CAN'T ADD SONGS AGAIN WITH CASE 1, YOU HAVE TO USE CASE 4)
* User wants to print the songs again with the print case 3
* Program prints out trash values and the old songs that printed out nicely before are now trash also.
我似乎无法理解我在做什么错。请有人启发我。
带有struct的lab3.h文件：
#ifndef LAB3_H
#define LAB3_H
#define SIZE 80
struct Song
{
char titel[SIZE];
char artist[SIZE];
int releaseD;
};
int menu(struct Song *songs);
#endif // !LAB3_H
编辑
（在main.c中，我确实具有_CrtSetDbgFlag（_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF）；以查找内存泄漏。）
最佳答案
在情况4的末尾有一个free（aSong）调用，因此数组的内容在菜单的递归调用中丢失了。希望这可以帮助。
关于c - C-动态分配会覆盖现有数据吗？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41921053/