c - 我一直收到 collect2 : error: ld returned 1 exit status

Question

我遇到了一些问题。每次尝试编译我的程序时，我都会收到“collect2: error: ld returned 1 exit status”。我在谷歌上搜索了这个，查看了示例，发现它通常发生在头文件未正确使用时；但是，我没有在我的代码中使用头文件，所以我不确定为什么要这样做。我认为这对其他遇到此错误但不明白原因的人会有所帮助。我确实知道我的代码中有很多错误，但我正在努力找到可以编译它并解决所有问题的地方。非常感谢!!

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

struct node_t {
    double x;
    struct node_t *next;
};

struct node_t *create_node(double n);
void print_node (struct node_t * node ); 
void print_list (struct node_t * head );
struct node_t * insert_head (struct node_t *head , struct node_t * node );
struct node_t * insert_tail (struct node_t *head , struct node_t * node );
struct node_t * insert_middle (struct node_t *head , struct node_t *node , int pos );
int count_nodes (struct node_t * head );
struct node_t * delete_node (struct node_t *head , double n);
void delete_list (struct node_t * head ); 

int main (void) 
{

    double n;
    int pos;


/** Asks the user what they would like to do. */

    printf("Please select an option: ");
    printf("1. Enter a number ");
    printf("2. Delete a number ");
    printf("3. Print all numbers ");
    printf("4. Tell how many items in the list ");
    printf("5. End program ");
    printf("Please enter your choice (1, 2, 3, 4, 5): ");
    while ((tmp = getchar()) != '\n')
        in = tmp; /** Tells the compiler to use the number that the use put in. */

    switch (in){
    case '1': {/** If the user chooses Enter a Number, go through this process. */
        printf("1. Enter item at head of list ");
        printf("2. Enter item in middle of list ");
        printf("3. Enter item at tail of list ");
        printf("Please enter your choice (1,2,3): ");
        while ((tmp = getchar()) != '\n')
            in = tmp;

        switch (in) {
        case '1':{
            printf("Enter the number to be entered at head: ");

            fgets(s, 1024, stdin);

            struct node_t * create_node (double n);
            struct node_t *insert_head(struct node_t *head, struct node_t *node);

            break;
            }

        case '2':{
            printf("Enter the number to be entered in middle: ");

            fgets(s, 1024, stdin);

            struct node_t * create_node (double n);
            struct node_t * insert_middle (struct node_t *head , struct node_t *node , int pos);
            break;
            }

        case '3':{
            printf("Enter the number to be entered at tail: ");

            fgets(s, 1024, stdin);

            struct node_t * create_node (double n);
            struct node_t *insert_tail(struct node_t *tail, struct node_t *node);

            break;
            }
        break;
            }
        }   

    case '2':{/** If the user selected Delete a Number, go through this process. */ 

        printf("Enter the node that needs to be deleted: ");

        fgets(s, 1024, stdin);

        struct node_t * delete_node (struct node_t *head , double n);

        break;

        }   

    case '3':{/** If the user selected Print All Numbers, go through this process. */

        //void print_list (struct node_t *head)

        break;

        }

    case '4':{ /** If the user selected Tell How Many Items in the List, go through this process. */
        int count_nodes (struct node_t * head );        

        break;
        }

    case '5':{ /** If the user selected End Program, go through this process. */

        return 1;       

        break;
        }

    }       

    return 0;

}







/** Creates a new node
 *  @param double n, a number n
 *  @return pointer
 */

struct node_t * create_node (double n)
{


    struct node_t *p = malloc (size of (struct node_t))
    p -> x = n;
    p -> next = NULL; /*initializes pointer to null*/
    return p;
}


/** Prints the nodes
 *  @param struct node_t *node
 */
//void print_node (struct node_t *node )
//{
//  prints out the node and the address of the node
//  print(*node, &node)
//}


/** Prints list
 *  @param struct node_t *head
 */
//void print_list (struct node_t *head)
//{
//  print contents of list. both the doubles and the address.
//  while (pointer is pointing to something, keep going through the list. )
//  print(nodes in list, address of nodes )
//}


/** Inserts a node at the head
 *  @param struct node_t *head, the structure where head is. 
 *  @param struct node_t *node, the structure where node is.
 *  @return head.
 */
struct node_t *insert_head(struct node_t *head, struct node_t *node)
{
    node-> next = head;
    head = node;
    return head;
}


/** Inserts a node at the tail.
 *  @param struct node_t *tail, the structure where tail is. 
 *  @param struct node_t *node, the structure where node is.
 *  @return head.
 */
struct node_t *insert_tail(struct node_t *tail, struct node_t *node)
{

    struct node_t *p = head;
    if (head == NULL)
        head = node;
        return head;
    while (p->next ! = NULL)
        p = p-> next;
        p-> next = node;
        return head;
}


/** Inserts a node at the middle.
 *  @param struct node_t *head, the structure where head is. 
 *  @param struct node_t *node, the structure where node is.
 *  @param int pos, the position of the current node.
 *  @return head.
 */
struct node_t * insert_middle (struct node_t *head , struct node_t *node , int pos);
{

    int pos = 1;
    struct node_t *p = head;
    *head = pos, pos = 1;
    if (pos > SIZE )
        p-> next = node;
    else if (pos < 1)
        printf("Error\n");
    return head;
}


/** Counts the number of nodes
 *  @param struct node_t *head, the structure where head is. 
 *  @return count.
 */
int count_nodes (struct node_t * head );
{

    struct node_t *p = head;
    while(p->next ! = NULL)
        return count;
    if (head == NULL)
        count = 0;
    return count;
}   

/** Deletes nodes
 *  @param struct node_t *head, the structure where head is. 
 *  @param double n, a number n.
 *  @return head.
 */ 
struct node_t * delete_node (struct node_t *head , double n);
{

    if (node == head)
        free head;
        p->next = head; //head now points to the pointer that was next after the node that was deleted

    else if (node == middle)
        free node;
        p = p->next //pointer before node that was deleted now points to node that was after deleted node

    else if (node == tail)
        free p = p->next = node; //free the last node that holds data. The node before it now points to NULL
        p->next = NULL;

    else printf("Error\n")
    return head;
}


/** Deletes list
 *  @param struct node_t *head, the structure where head is. 
 *  @return head.
 */ 
void delete_list (struct node_t * head ); 
{
    while((p->next ! = NULL)
        free head; //This will lose all memory after head.
        head == NULL;
    if (head == NULL) 
        return 0;
    return 0;
}

Answer 1

那是链接器失败的时候。

您的文件顶部的前向声明签名可能与下面的实现不匹配。链接器找不到其中一个函数。