c - 将节点插入链表期间出现分段错误

Question

我正在尝试在我的add函数中按字母顺序排列两个单独的列表：一个按名字对节点进行排序，另一个按姓氏排序。我还有一些逻辑可以检查名称是否已在列表中，如果它是错误，则打印并且列表返回不变。就像标题所说，我在这里遇到了一个分段错误，不知道为什么。这可能是一个非常基本的问题，但我是C新手，尤其是链表新手。

以下是节点的定义方式：

typedef struct node {
    char *first;
    char *last;
    long number;
    struct node *nextFirst;
    struct node *nextLast;
} Node;
typedef struct mlist {
    Node *headFirstName;
    Node *headLastName;
} MultiLinkedList;

这是我的添加函数：

MultiLinkedList *add(MultiLinkedList *list, char *first, char *last, long num) {
    // allocate a new node
    Node *newNode = malloc ( sizeof(Node) );
    newNode->first = malloc ( strlen(first) + 1 );
    strcpy(newNode->first, first);
    newNode->last = malloc ( strlen(last) + 1 );
    strcpy(newNode->last, last);
    newNode->number = num;
    //make placeholder nodes
    Node *a = list->headFirstName;
    Node *b = list->headLastName;
    // add this new node at the head of the "byFirst" list
    if (strcmp(newNode->first, a->first) < 0) {
            newNode->nextFirst = list->headFirstName;
            list->headFirstName = newNode;
    }
    for (Node *i = list->headFirstName; i; i = i->nextFirst) {
            // add after less alphabetical nodes
            if (strcmp(newNode->first, i->first) > 0) {
                    newNode->nextFirst = i->nextFirst;
                    i->nextFirst = newNode;
            }
            // return error for duplicate name
            if (strcmp(newNode->first, i->first) == 0 && strcmp(newNode->last, i->last) == 0) {
                    printf("That person is already in the list! Please try with a different name.n");
            }
    }
    // add this new node at the head of the "byLast" list
    if (strcmp(newNode->last, b->last) < 0) {
            newNode->nextLast = list->headLastName;
            list->headLastName = newNode;
    }
    for (Node *j = list->headLastName; j; j = j->nextLast) {
            // add after less alphabetical nodes
            if (strcmp(newNode->last, j->last) > 0) {
                    newNode->nextLast = j->nextLast;
                    j->nextLast = newNode;
            }
    }
    // return the multi-list object with updated or original head pointers
    return list;
}

Answer 1

我弄清楚了我的问题是什么。我必须在每个 if 语句的末尾添加 return list;，否则该函数会尝试执行每个 true 语句;这会导致赛格故障。事后看来，我很惊讶我没有早点弄清楚这一点。