Question

我有一个包含指针next的结构。我试图建立一个结构队列，但是当我调用enqueue/dequeue时，我最终会在尝试写信息时遇到错误;并且不知道它是否归因于enque/dequeue/insert。只是学习C并且不确定free/malloc或者是否有必要。 Insert基于int值（最小值优先）。

struct queue { 
    struct RCB* front; 
    struct RCB* back; 
};

/*Initialize queue */ 
struct queue* new_queue(void){
    struct queue* tmp = malloc( 1 * sizeof(tmp));  
    tmp->front = NULL; 
    tmp->back = NULL;
    return tmp;  
}

/*Add RCB to Queue FIFO */
struct queue* enqueue(struct queue* queue, struct RCB* rcb){
    if(queue->front == NULL && queue->back == NULL){
        queue->front = rcb; 
        queue->back = rcb;
            printf("added front to queue\n");  
        return queue; 
    }
    else {
        queue->back->next = rcb; 
        queue->back = rcb;
            printf("added to queue\n");  
    }
    return queue; 
} 

/*Remove RCB from Queue FIFO */ 
struct RCB* dequeue(struct queue* queue){
    struct RCB *tmp1 = (struct RCB *)malloc(sizeof(struct RCB)); 
    struct RCB *tmp2 = (struct RCB *)malloc(sizeof(struct RCB)); 
    if(queue->front == NULL && queue->back == NULL){
        printf("queue is empty\n"); 
    }   
    tmp1 = queue->front; 
    tmp2 = tmp1->next; 
    queue->front = tmp2; 
    if(queue->front == NULL){
        queue->back = queue->front;
            printf("removed rcb from queue\n");  
    }
    return tmp1; 
}
/*Insert RCB into Queue */ 
 struct queue* insert(struct queue* queue, struct RCB* rcb){
            if(queue->front == NULL && queue->back == NULL){
                queue->front = rcb; 
                queue->back = rcb;
                return queue; 
            }
            if(queue->front->next == NULL){
                queue->front->next = rcb; 
                return queue; 
            }

            struct RCB *tmp = (struct RCB *)malloc(sizeof(struct RCB));
                    tmp = queue->front; 
                        while(tmp->next->b2r < rcb->b2r || tmp->next == NULL){
                        tmp = tmp->next;
                    }
                    rcb->next = tmp->next; 
                    tmp->next = rcb; 

                    return queue; 
    }

非常感谢任何帮助。

Answer 1

Do not cast malloc return value

new_queue

，struct queue* tmp = malloc( 1 * sizeof(tmp));是错误的，因为这会分配一个指针大小为struct queue的缓冲区，而不是struct queue的大小，也是1*foo事情根本没用。使用以下：
```
struct queue* tmp = malloc(sizeof(*tmp));
```

在dequeue中，您正在分配两个struct RCB的缓冲区，同时通过分配指针tmp1 and tmp1暂时丢失对它们的引用，这些不是必需的，而您是造成内存泄漏。你需要的只是两个指针：

struct RCB* dequeue(struct queue* queue) {
        struct RCB *tmp1; 
        struct RCB *tmp2; 
        if(queue->front == NULL && queue->back == NULL) {
            printf("queue is empty\n"); 
        }   
        tmp1 = queue->front; 
        tmp2 = tmp1->next; 
        queue->front = tmp2; 
        if(queue->front == NULL) {
            queue->back = queue->front;
                printf("removed rcb from queue\n");  
        }
        return tmp1; 
}

在队列中排队/出队/插入结构

1 个答案: