c - 除非我在其他所有内容之前添加 printf，否则我的 C 程序无法运行

Question

我尝试运行代码，它终止并且不打印任何内容，但如果我在主代码的第一行包含 printf 语句，它就会起作用。为什么？

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

typedef struct node TNode;
typedef struct list TList;

struct list{
    TNode *node;
};

struct node{
    int data;
    TNode *next;
};

TList* buildList(){
    TList *list;
    list = (TList*)malloc(sizeof(TList));
    list->node->next = NULL;
    printf("\nList was built successfully\n");
    return list;
}


int main(){
    TList *myList = buildList();
    myList->node->data = 5;
    printf("\nData: %d\n", myList->node->data);
    return 0;
}

Answer 1

您正在访问list->node->next，但尚未初始化list->node。为节点分配内存，并将指向该节点的指针分配给list->node。

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

typedef struct node TNode;
typedef struct list TList;

struct list{
    TNode *node;
};

struct node{
    int data;
    TNode *next;
};

TList* buildList(){
    TList *list;
    list = (TList*)malloc(sizeof(TList));
    list->node = (TNode*)malloc(sizeof(TNode));    // <---
    list->node->next = NULL;
    printf("\nList was built successfully\n");
    return list;
}


int main(){
    TList *myList = buildList();
    myList->node->data = 5;
    printf("\nData: %d\n", myList->node->data);
    return 0;
}