c - 函数不返回

Question

struct m_queue{
       int ndata;
       struct m_queue* pnext;
       struct m_queue* pdown;
       };

 int search(struct m_queue* list,int key){  //returns the index where it founded the key, return -1 if key is not found
        struct m_queue* temp;//searches horizontal
        struct m_queue* run;//searches downward
        int i;
        temp = list;

        run = temp->pdown;

        getch();
        while(temp!=NULL){

            getch();
            while(run!=NULL){
                if(run->ndata == key)
                    return temp->ndata;
                else
                    run = run->pdown;
            }
            temp = temp->pnext;
            run = temp->pdown;

        }
        printf("returning -1");
        getch();
        return -1;

    }

我已经检查了其他函数，我很确定没有缺陷，但每当我调试程序时，它总是突出显示“run = temp->pdown”段。这个函数不返回-1，它只是在找到 key 时返回。这是用c语言编写的

Answer 1

如果temp为NULL，则run = temp->pdown;是无效操作。

}
temp = temp->pnext;
if (temp!=NULL)  //add this line
    run = temp->pdown;