打印链表会导致字符串带有垃圾值 (C)

Question

我正在从.txt文件中读取链表以填充以下节点：

typedef struct node {

int data;
char* line;
struct node* next;
} NODE;

代码工作正常，并将文件读入链表。我在初始化每个节点时打印出字符串。但是，每当我调用printList()函数时，line字符串始终是垃圾值。示例运行：

./a.out linkedlisttext.txt
data in readFile(): 4
string in readFile():  Hello world
address in readFile(): 0x1326067a0

data in readFile(): 28
string in readFile():  What is up world???
address in readFile(): 0x1326067c0

data in readFile(): 2124
string in readFile():  your mother
address in readFile(): 0x1326067e0

data in readFile(): 85
string in readFile():  more data
address in readFile(): 0x132606800

data in readFile(): 9421
string in readFile():  just a little more data
address in readFile(): 0x132606820

data in readFile(): 992
string in readFile():  are we almost there?
address in readFile(): 0x132606840

data in readFile(): 301
string in readFile():  we did it!
address in readFile(): 0x132606860
DATA:    4 | STRING �g`2
address in printList(): 0x1326067a0
DATA:   28 | STRING �g`2
address in printList(): 0x1326067c0
DATA: 2124 | STRING �g`2
address in printList(): 0x1326067e0
DATA:   85 | STRING h`2
address in printList(): 0x132606800
DATA: 9421 | STRING 0h`2
address in printList(): 0x132606820
DATA:  992 | STRING Ph`2
address in printList(): 0x132606840
DATA:  301 | STRING 
address in printList(): 0x132606860

这是linkedlisttext.txt

4, Hello world
28, What is up world???
2124, your mother
85, more data
9421, just a little more data
992, are we almost there?
301, we did it!

这是代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct node {

int data;
char* line;
struct node* next;
} NODE;

struct node* readFile(FILE* fp, NODE* root) {
char line[100];
char* token;
NODE* curr;
NODE* prev;

while(fgets(line, 100, fp) != NULL) {   

curr = malloc(sizeof(struct node*));
token = strtok(line, ",");

curr->data = atoi(token);
printf("ndata in readFile(): %dn", curr->data);

token = strtok(NULL, "");
curr->line = (char*) malloc(sizeof(token)  + 1);
strcpy(curr->line, token);
printf("string in readFile(): %s", curr->line);
printf("address in readFile(): %pnn", curr->line);

curr->next = NULL;  


if(root == NULL) {
root = curr;
} else {
NODE* travel = root;
while(travel->next != NULL) {
travel = travel->next;
}
travel->next = curr;
}

}
return root;    
}
void printList(NODE* root) {

struct node* temp = root;
while(temp->next != NULL) {
printf("DATA: %4d | STRING %sn", temp->data, temp->line);
printf("address in printList(): %pn", temp->line);

temp = temp->next;
}
printf("DATA: %4d | STRING %sn", temp->data, temp->line);
printf("address in printList(): %pn", temp->line);
}
int main(int argc, char** argv) {

FILE* fp = fopen(argv[1], "r");
NODE* root = NULL;  
if(fp == NULL) {
return 0;
}   
root = readFile(fp, root);
printList(root);

}

任何帮助不胜感激，谢谢！

Answer 1

curr->line = (char*) malloc(sizeof(token) + 1);

由于sizeof(token)总是返回指针的大小(大多数系统为 8 字节)， 不是字符串的长度，您没有为line分配足够的缓冲区。请尝试：

curr->line = malloc(strlen(token) + 1);

作为旁注，您对 main 函数中的行缓冲区和结构成员名称使用相同的名称line。它们具有单独的命名空间且语法有效，但可能会使将来的维护感到困惑。

Answer 2

这是非常可疑的：

curr = malloc(sizeof(struct node*));

您正在为struct node指针分配内存，但不为struct node分配内存。给定指针和整数的内存大小，随后分配给curr->data可能实际上有效，但随后分配给curr->line和curr->next可能会给您带来麻烦。

或者不是。未定义的行为本质上是不可预测的。