c - printf 期间数据被修改

Question

从文件中读取一些数据后，将其分配给节点内的结构类型记录，数据与文件的数据匹配。在我离开读取功能并返回主程序后，数据仍然保持不变。但当我尝试打印它时，它变得一团糟。

加载函数

void load(FILE *file, Node *head)
{
    char tempArtist[30]={'\0'}, tempAlbum[30]={'\0'}, tempTitle[30]={'\0'}, tempGenre[30]={'\0'},tempSpace='\0';
    SongLength *tempLength=NULL;
    int tempPlay=0, tempRating=0, tempMins=0, tempSecs=0;

    tempLength = (SongLength*)malloc(sizeof(SongLength));

    fscanf(file,"%s",&tempArtist);
    fscanf(file,"%s",&tempAlbum);
    fscanf(file,"%s",&tempTitle);
    fscanf(file,"%s",&tempGenre);
    fscanf(file,"%s",&tempMins);
    fscanf(file,"%s",&tempSecs);
    fscanf(file,"%s",&tempPlay);
    fscanf(file,"%s",&tempRating);
    fscanf(file,"%c",&tempSpace);

    tempLength->mins=&tempMins;
    tempLength->secs=&tempSecs;

    head->data->album=tempAlbum;
    head->data->artist=tempArtist;
    head->data->genre=tempGenre;
    head->data->song=tempTitle;
    head->data->length=tempLength;
    head->data->played=tempPlay;
    head->data->rating=tempRating;
}

打印测试功能

int main(void)
{
    FILE *loadFile = NULL;
    Node *head=NULL;

    head=(Node*)malloc(sizeof(Node));
    head->data=(Record*)malloc(sizeof(Record));
    head->data->length=(SongLength*)malloc(sizeof(SongLength));

    loadFile=fopen("records.txt","r");

    load(loadFile,head);
    head->data->artist; // artist matches the name in load file (aka snoop)
    printf("%s", head->data->artist); // When trying to print here it prints a smiley face
}

方便复制的额外信息

typedef struct songlength
{
    int *mins;
    int *secs;
}SongLength;


typedef struct record
{
    char *artist;
    char *album;
    char *song;
    char *genre;
    struct songlength *length;
    int played;
    int rating;

}Record;

typedef struct node
{
    struct node *pPrev;
    struct record *data;
    struct node *pNext;

}Node;

文件数据格式

snoop
heartbeat
swiggity
rap
03
10
25
4

Answer 1

您有undefined behavior因为您将指向本地数组的指针分配给 head 结构。

例如，一旦函数 load 返回，数组 tempArtist 将超出范围，因此任何指向该数组的指针(例如head->artist)将是杂散指针，取消引用这些指针将导致上述未定义的行为。