SegFault返回声明C.

Question

我对此代码的问题是当我试图在第一次迭代时返回addTrash函数中的struct node * head。我怀疑它可能是堆栈损坏但我不确定并且我不确切地知道我将如何弄清楚我给你的代码中的错误是什么。

这是一个双向链接的链表，它具有唯一的数据值。

struct node * modifyMainList( struct node *head, int link2Delete){

    struct node * curr = head;
    struct node * temp;
    int i = 0;  

    //traverse list link2Delete amount of times
    while(i != link2Delete){

        curr = curr -> next;
    }


    //head case
    if(curr -> previous == NULL){

        curr = curr -> next;            

        head = curr;
        return head;
    }

    //tail case 
    if(curr -> next == NULL){

        temp = curr;    
        curr = curr -> previous;

        curr -> next = NULL;
        temp -> previous = NULL;
        temp -> next = NULL;

        free(temp);
        return head;
    }

    curr -> previous -> next = curr -> next;
    curr -> next -> previous = curr -> previous;            


    curr -> previous = NULL;
    curr -> next = NULL;
    free(curr);
    return head;
}



struct node * addTrash(struct node *mainHead, int link2Delete){

    struct node * head = NULL;
    struct node * curr = mainHead;
    struct node * trashCurr = NULL;;
    struct node * temp = NULL;
    int i = 0;  

    printf("im in trash before loop\n\n");
    for(i = 0; i < link2Delete; i++){

        curr = curr -> next;
    }

    printf("im in trash before head size check\n\n");
    if(head == NULL){

        printf("im in trash with head == null\n\n");
        //head of main list
        if(link2Delete == 0){

            printf("im in trash link2delete == null\n\n");
            curr = curr -> previous;
            head = curr;

            curr = curr -> next;
            curr -> previous = NULL;
            curr -> next = NULL;
            return head;
        }

        printf("im in trash before tail case\n\n");
        //tail of main list
        if(curr -> next == NULL){


            printf("im in trash with tail case\n\n");
            head = curr;

            head -> previous = NULL;
            return head;
        }

        printf("im in trash before after tail case\n\n");

        //every other case

        //printf("this is the head value: %d\n\n", head -> value);
        head = curr;
        //printf("im in trash after head = curr\n\n");

        head -> previous = NULL;
        //printf("im in trash after head -> previous\n\n");

        head -> next = NULL;
        printf("im in trash after head -> next\n\n");

        printf("this is the head value: %d\n\n", head -> value);
        return head;

    }else{

        printf("im in trash inside else\n\n");
        trashCurr = head;
        while(trashCurr -> next != NULL){

            trashCurr = trashCurr -> next;
        }

        if(link2Delete == 0){

            temp = curr; 
            trashCurr -> next = temp;

            temp -> previous = trashCurr;
            trashCurr = temp;
            trashCurr -> next = NULL;
            return head;
        }

        //tail of main list
        if(curr -> next == NULL){

            temp = curr;
            trashCurr = temp;

            temp -> previous = trashCurr;           
            temp -> next = NULL;
            trashCurr -> next = temp;

            return head;
        }

        //every other case

        temp = curr;    
        temp -> previous = trashCurr;

        trashCurr -> next = temp;
        trashCurr = temp;
        trashCurr -> next = NULL;
        return head;

    }


}


void generateRandom(struct node *mainHead, int size){
    int i = 0;
    int link2Delete = 0;
    struct node *head = NULL;
    srand ( time(NULL) );
    int number2Delete = rand() % size + 1;


    printf("this is the rand number: %d\n", rand());    

    printf("this is the number of nodes to be deleted: %d\n", number2Delete);

    for (i = 0; i < number2Delete; i++) {
        // Pick a random node (payload) to delete.  
        link2Delete = (rand() % size);
        printf("this is the number of nodes in the list: %d\n", size);
        printf("this is the node to be deleted: %d\n", link2Delete);
        size--;

        if(link2Delete == 0){
            mainHead = modifyMainList(mainHead, link2Delete);
            //printf("this is the call return: %d\n\n",  addTrash(mainHead, link2Delete) -> value);
            head = addTrash (mainHead, link2Delete);

        }else{

            head = addTrash (mainHead, link2Delete);
            mainHead = modifyMainList(mainHead, link2Delete);
        }

    }
    return;
}

Answer 1

在您的代码中，

while(i != link2Delete){

    curr = curr -> next;
}

如果link2Delete!=0，

是一个无限循环。

而且，不要在head case中释放。

由于循环是无限的，curr = curr->next将继续重复，它将指向一些垃圾指针（如果循环条件为真）。然后，它有未定义的行为。你可能会得到SEGFAULT。