c - 访问结构时出现段错误

Question

当我执行 level->description 的 printf 命令时，程序给出段错误。我不知道为什么。我应该使用 malloc 来修复它吗？文件 sokoban.dat 的内容(只有 1 行以 '\n' 结尾)是“chicago;addie;story begin here;-----#####-----------| ----#@$.#------------|-----######-----------"

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

typedef struct {
char *name;
char *description;
char *password;
char *map;
struct level *next;
//char *solution;
} LEVEL;

LEVEL* parse_level(char *line) {   //parsing from file into the structure
    LEVEL level;
    char level_name[50];
    char level_password[50];
    char level_description[100];
    char level_map[200];

    int i = 0;
    int j = 0;
    while (line[i] != ';') {      //getting level name
        level_name[j] = line[i];
        i++;
        j++;
    }
    level_name[j]='\0';
    level.name=&level_name[0];
    //strcpy(&level.name,level_name);
    //printf("%s\n",level.name);
    printf("%s\n",level_name);
    j = 0;
    i++;
    while (line[i] != ';') {     //getting level password
        level_password[j] = line[i];
        i++;
        j++;
    }
    level_password[j]='\0';
    level.password=&level_password[0];
    printf("%s\n",level_password);
    j = 0;
    i++;
    while (line[i] != ';') {     //getting level description
        level_description[j] = line[i];
        i++;
        j++;
    }
    level_description[j]='\0';
    level.description=&level_description[0];
    printf("%s\n",level_description);
    j = 0;
    i++;
    while (line[i] != '\n') {    //getting level map
        level_map[j] = line[i];
        i++;
        j++;
    }
    level_map[j]='\0';          
    level.map=&level_map[0];
    printf("%s\n",level_map);
    j = 0;
    level.next=NULL;    
    LEVEL* levelPointer=&level;
    return levelPointer;
}  
int main(){
    FILE *fp = fopen("sokoban.dat", "r");
    if( fp == NULL ){
        printf("No such file\n");
        return 1;
    }

    char line[500];
    //strcpy(line,"");
    char c;
    int i=0;
    while((c = fgetc(fp)) != '\n'){ //reading from file 1 by 1 character
       line[i]=c;
       i++;
    }
    printf("%s\n",line);
    LEVEL* level;
    level=parse_level(line);
    //printf("%s\n",level->description);   **//!!! this is where error occur**
    printf("%s\n",level->map);

    return 0;
}

Answer 1

在函数 parse_level() 中，您获取所有局部变量的地址并将其复制到 struct 变量 level 中并返回 级别。所有这些本地地址的副本以及在其生命周期之后使用这些对象都会使您的程序非法并导致 undefined behaviour 。

在深入研究之前，您应该首先阅读语言基础知识，并了解指针、数组、函数返回值、返回指针等概念。

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