C链表searchNode/freeList方法(seg fault)

Question

我一直在为类(class)从 Java 过渡到学习 C。当前的练习是为 LinkedList 实现 removeAtFront()、searchNode() 和 freeList() 方法。我从理论上理解这是如何工作的——我会用 Java 快速完成它，我已经尝试了几个小时，但不明白为什么下面的代码不起作用。

删除方法似乎有效，生成正确的修改列表，直到删除节点后调用搜索方法。然后总是产生seg fault 11。 free 方法也总是会产生段错误。

我不是要别人做我的作业，但如果我能指出正确的方向，我将不胜感激!

给定的 Node* 结构是:

typedef struct Node
{
  char  *word;
  struct Node  *next;
} Node;

main() 之外的方法是这样的:

void insertAtFront( Node **head, char * key )
{
    Node *new =  malloc( sizeof(Node) );
    if (!new)  fatal("Malloc of new Node failed");
    new->word = key;
    new->next = *head;
    *head = new;
}

void insertAtTail( Node **head, char * word )
{
    if (!(*head)) insertAtFront(head, word);    
    else insertAtTail(&(*head)->next, word);
}

void removeAtFront( Node ** head )
{
    Node *tmp = *head;
    if (!tmp) return;

    *head = tmp->next;
    free(tmp->word);
    free (tmp); 
}

void removeNode( Node ** head, char * key )
{
    Node *tmp = searchNode(*head, key);
    if (tmp) removeAtFront (&tmp);
}

Node * searchNode ( Node * head, char * key )
{   
    if (!head || (strcmp(head->word, key) == 0)) return head;
    return searchNode(head->next, key);
}

void freeList(  Node ** head )
{
    if (!head) return;
if (&(*head)->next) freeList (&(*head)->next);
    removeAtFront(head);
}

编辑:其中一条评论解决了我的 freeList() 方法问题，但其他人要求提供更多代码。这个赋值的问题是我只被允许修改 insertAtTail()、removeAtFront()、remove()、search() 和 freeList() 方法。不过，我将在下面发布主要方法。不过，我认为单词值在其中的分配是正确的。

Node *searchNode( Node * head, char * key );
void insertAtFront( Node **head, char * key );  // ALREADY WRITTEN FOR YOU 
void insertAtTail( Node **head, char * key );
void removeAtFront( Node ** head );
void removeNode( Node **head, char * key );
void freeList( Node **head );
void printList( Node * head ); // ALREADY WRITTEN FOR YOU
void fatal( char * msg ); // ALREADY WRITTEN FOR YOU

#define BUFFER_CAP 20

int main() 
{
  Node *head = NULL;

  while (1)
  {
    char option;
    printf("\nChoose 'H'ead Insert, 'T'ail insert, 'R'emove, 'S'earch, F'ree,     'Q'uit " );
    fflush( stdout );
    int result = scanf(" %c%*[^\n]", &option); getchar();  // MAGIC BULLET TO CORRECTLY READ A SINGLE CHAR FROM STDIN
    if (result <1) fatal("failure reading from stdin\n");

    if (option == 'H' )
    {
        char * word=malloc(BUFFER_CAP);  // DONT ENTER ANY LONG WORDS!
        printf("Enter a word to insertAtFront: " );
        fflush( stdout );
        char * result = fgets( word, BUFFER_CAP, stdin );
        if (result==NULL) fatal("failure reading from stdin\n");
        strtok(word,"\n"); // overwrites '\n' with  '\0'
        insertAtFront( &head, word ); /* shallow copy string into list   */
        printList( head );
    }
    if (option == 'T' )
    {
        char * word=malloc(BUFFER_CAP);  // DONT ENTER ANY LONG WORDS!
        printf("Enter a word to insertAtTail: " );
        fflush( stdout );
        char * result = fgets( word, BUFFER_CAP, stdin );
        if (result==NULL) fatal("failure reading from stdin\n");
        strtok(word,"\n"); // overwrites '\n' with  '\0'
        insertAtTail( &head, word ); /* shallow copy string into list   */
        printList( head );
    }
        if (option == 'R' )
    {
        char * word=malloc(BUFFER_CAP);  // DONT ENTER ANY LONG WORDS!
        printf("Enter a word to remove: " );
        fflush( stdout );
        char * result = fgets( word, BUFFER_CAP, stdin );
        if (result==NULL) fatal("failure reading from stdin\n");
        strtok(word,"\n"); // overwrites '\n' with  '\0'
        removeNode( &head, word );
        printList( head );
        free( word ); // we were just using it for matching
    }
    if (option == 'S' )
    {
        char * word=malloc(BUFFER_CAP);  // DONT ENTER ANY LONG WORDS!
        printf("Enter a word to find: " );
        fflush( stdout );
        char * result = fgets( word, BUFFER_CAP, stdin );
        if (result==NULL) fatal("failure reading from stdin\n");
        strtok(word,"\n"); // overwrites '\n' with  '\0'
        if (searchNode( head, word ))
            fprintf(stderr, "%s FOUND\n",word );
        else
            fprintf(stderr, "%s NOT FOUND\n",word );
        printList( head );
        free( word ); // we were just using it for matching
    }
    if (option == 'F' ) // free the entire list (remember to set head to NULL)
    {
        freeList( &head );
        printList( head );
    }
    else if (option == 'Q' )
        exit( 0 );
} // END WHILE

return 0;
}

Answer 1

当您使用 Node *new = malloc( sizeof(Node) ); 为节点分配内存时，您是为指针而不是数据分配内存。您确实为 char 分配了内存，例如:(这只是一个想法)

new->word= malloc(sizeof(char)*(strlen(key) + 1));
strcpy(new->word, key)

否则你必须使用你为 key 动态分配内存。 (因为您执行 free(tmp->word);)

_{我认为你应该再放一些代码。你如何传递 key？}