c - 不存储数据的结构指针的全局数组

Question

我有一个试图表示房屋布局的 C 程序。它从具有以下格式的文本文件中读取房间:

RoomDoorDoor*RoomDoorDoor

The rooms and doors are stored as structures, and I have a global array of pointers to store 10 rooms. I'm using the method readrooms() to read in the rooms from the text file and store them in the array. However, after reading it in, when I try to print the contents of the array, I get a string of random characters.

#include <stdio.h>
#define MAX 10
struct room * rooms[MAX];
int rp = 0; //room count

//Declare Structures
struct room {
    char *name;
    struct door *doors[4];
    int dp; //door count
};

struct door {
    char *name;
    struct room *room;
};

//Declare Functions
char *readLine(FILE *fin);
readrooms(FILE *fin);
struct  door *newDoor(char * name);
struct room *newRoom(char *name);

main(int argc, char const *argv[])
{
    FILE *f = fopen("C:\\Users\\s\\Documents\\C\\explore\\rooms.txt", "r");
    readrooms(f);
    printf("\n----- READ FILE SUCCESSFULLY | Room Count: %d -----\n", rp);

    for (int i = 0; i < rp; i++) {
        if (rooms[i] != NULL) {
            struct room r = *rooms[i];
            printf("ROOM %d: %s\n", i, r.name);
        }
    }


    return 0;
}

struct  door *newDoor(char * name) {
    struct door d;

    //TODO: MAKE SURE THIS IS RIGHT
    d.name = name;
    d.room = NULL;

    return &d;
}

struct room *newRoom(char *name) {
    struct room r;

    r.name = name;
    r.dp = 0;

    rooms[rp++] = &r;

    return &r;
}

char *readLine(FILE *fin) {
    char *str = (char *) malloc(sizeof(char) * 3);
    char current = fgetc(fin);
    int iter = 0;
    while (1) {
        if (current == '\n') {
            str[iter] = '\0';
            break;
        }
        else if (current == EOF) return NULL;
        else {
            str[iter++] = current;
           current = fgetc(fin);
        }
    }
    return str;
}

readrooms(FILE *fin) {
    char *curr_room = readLine(fin);

    while (curr_room != NULL) {
        if (strcmp(curr_room, "*") == 0) {
            curr_room = readLine(fin);
            continue;
        }
        struct room r = *newRoom(curr_room);
        printf("\n\nReading room %s\n", r.name);

        curr_room = readLine(fin);
        while (curr_room != NULL && strcmp(curr_room, "*") != 0) {
            struct door d = *newDoor(curr_room);
            d.room = &r;
            r.doors[r.dp++] = &d;

            printf("\t%s.doors[%d] = %s\n", r.name, r.dp-1, d.name);
            curr_room = readLine(fin);
            //printf("Current room is now %s\n\n", curr_room);
        }
    }

}

这是输出:

Reading room Hall
        Hall.doors[0] = Study
        Hall.doors[1] = Cellar
        Hall.doors[2] = Kitchen


Reading room Study
        Study.doors[0] = Hall
        Study.doors[1] = Garden


Reading room Cellar
        Cellar.doors[0] = Hall


Reading room Kitchen
        Kitchen.doors[0] = Hall
        Kitchen.doors[1] = Garden


Reading room Garden
        Garden.doors[0] = Study
        Garden.doors[1] = Kitchen

----- READ FILE SUCCESSFULLY | Room Count: 5 -----
ROOM 0: ├ïuΣ uαΦ┤■  Y├jhxÖä
ROOM 1: É√o
ROOM 2: É√o
ROOM 3: É√o
ROOM 4: É√o

Answer 1

一个问题。

struct room *newRoom(char *name) {
    struct room r;

    r.name = name;
    r.dp = 0;

    rooms[rp++] = &r;

    return &r;
}

struct room r; 是局部变量，一旦控制退出 newRoom 函数就会消失。

相反，你可以做的是

struct room *r = malloc(sizeof(struct room));
r->name = name;
r->dp = 0;

rooms[rp++] = r;

---

在 readLine 中分配足够的内存来读取完整的行，否则您最终会越界访问并调用未定义的行为。

 char *readLine(FILE *fin) {
    char *str = (char *) malloc(sizeof(char) * 256);
                                                 ^^^Max line length
     ...
  }

如果你不想盲目地分配内存，realloc 就是你要找的东西。