链接列表无法正常运行

Question

我正在创建一个链表类型的数据结构，但不完全是。到目前为止，我有以下内容，但问题是，在此方法完成后，只有第一个链接仍然存在，第一个链接之后的链接消失了。这里有什么问题？

//Global Vars
m_p H = NULL; //m_p is the struct

func(){
    /* .... */
    H = malloc(sizeof(m_r));
    H->next = NULL;
    H->previous = NULL;
    m_p p = H;
    for(i = 0; i < nLists; i++){
        m_p n = malloc(sizeof(m_r));
        n->next = NULL;
        n->previous = p;
        p->next = n;

        p = p->next;
    }
  //if I iterate through the links here, they all print out fine

  m_p x = H;
  while(x != NULL){
     printf("%d ", x->data);
     x = x->next;
  }
}

既然 H 是一个全局变量，链接不应该保持原样吗？当我尝试遍历同一文件中另一个函数中的链接时，它们不存在，只有第一个存在。我做错了什么？

编辑：我省略了在每个结构中设置数据字段以保持代码简洁的部分。

编辑2：这是另一个文件中的一个函数，这是发生错误的地方：

extern m_p H;

m_p func2(int s) {

  int n_s = ALIGN(s);
    m_p p = H;

    while(p != NULL ){
        printf("1. %d \n", p->data);
        p = p->next; //this is always NULL even if there were more than one node previously in func()
        if(p == NULL) printf("LINK NOT PRESENT \n");    
    }

  /* ... */

}

这也是我的结构的样子：

typedef struct m{
    struct m *next;
    struct m *previous;
    int data;

} m_r, *m_p;

Answer 1

据我所知，您的代码看起来不错。 BLUEPIXY 提供的代码有效，所以我必须同意 BLUEPIXY。您的问题可能在其他地方。这是我在电脑上测试的代码（和BLUEPIXY's code很像）。

list.h

struct node {
    struct node *previous, *next;
    int data;
};

void linkedList();
void anotherFunction();
void freeMemory();

list.c

#include <stdlib.h> // malloc, free
#include <stdio.h> // printf
#include "list.h"

// Global variable
struct node *m_root;

void linkedList(){
    m_root = malloc(sizeof(struct node));
    m_root->data = -1;
    m_root->next = NULL;
    m_root->previous = NULL;
    int i;
    int n = 10;
    struct node *prev = m_root;
    struct node *next;
    for(i=0;i<n;i++){
        next = malloc(sizeof(struct node));
        next->data = i;
        next->previous = prev;
        prev->next = next;

        prev = prev->next;
    }

    printf("Within linkedList\n");
    struct node *iter = m_root;
    while(iter!=NULL){
        printf("%d ",iter->data);
        iter = iter->next;
    }
    printf("\n");
}

void anotherFunction(){
    printf("Within anotherFunction\n");
    struct node *iter = m_root;
    while(iter!=NULL){
        printf("%d ",iter->data);
        iter = iter->next;
    }
    printf("\n");
}

void freeMemory(){
    printf("Freeing memory\n");
    struct node *current = m_root;
    struct node *next;
    while(next!=NULL){
        next = current->next;
        free(current);
    }
    m_root->next = NULL;
    m_root = NULL;
}

extern.c

#include <stdio.h>
#include "list.h"

extern struct node *m_root;

void anotherFileFunction(){
    struct node *iter = m_root;
    while(iter!=NULL){
        printf("1. %d\n",iter->data);
        iter = iter->next;
    }
}

int main(){
    linkedList();
    anotherFileFunction();
    freeMemory();
    anotherFileFunction();
    printf("Done!\n");
    return 0;
}

输出是：

Within linkedList
-1 0 1 2 3 4 5 6 7 8 9 
1. -1
1. 0
1. 1
1. 2
1. 3
1. 4
1. 5
1. 6
1. 7
1. 8
1. 9
Freeing memory
Done!