Styjun

When I use Xcode for C++ to edit a simple demo that is simulating a process, it gives an error:

 Undefined symbols for architecture x86_64: 
 "exit()", referenced from: 
 menu() in main.o 
 "kill()", referenced from: 
 menu() in main.o 
ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

In my limited experience with C++, I have never meet this problem, and I search for long time on net, but have no use.please help or try to give me some ideas how to achieve this. Thanks in advance.

My Xcode version is 10.1.

<!-- language: C++ -->
 #include<iostream>
 #include<string.h>
 #include<stdlib.h>
 #define OK 1
 #define ERROR 0
 #define OVERFLOW -2
 void create();
 void kill();
 void display();
 void exit();
 struct PCB
 
 char NAME[10];
 long ID;
 float TIME;
 int PRIORITY;
 ;PCB pcb[100];
 typedef struct QNode
 
 int data;
 struct QNode*next;
 QNode,*QueuePtr;
 typedef struct
 
 QueuePtr front;
 QueuePtr rear;
 LinkQueue;LinkQueue Ready,Empty;
 int InitQueue()
 
 Ready.front=Ready.rear=new QNode;
 Empty.front=Empty.rear=new QNode;
 Ready.front->next=NULL;
 Empty.front->next=NULL;
 return OK;
 
 void menu()
 
 std::cout<<"****=========="<<"1. 进程创建 n";
 std::cout<<"****=========="<<"2. 进程撤销 n";
 std::cout<<"****=========="<<"3. 就绪队列显示 n";
 std::cout<<"****=========="<<"4. 退出 n";
 int choice;
 std::cout<<" 请选择： ";
 std::cin>>choice;
 switch(choice)
 
 case 1:create();break;
 case 2:kill();break;
 case 3:display();break;
 case 4:exit();
 
 
 void create()
 
 char name[10];
 long id;
 float time;
 int priority;
 int n;
 QNode *p;
 std::cout<<" 请输入要创建进程的数目： ";
 std::cin>>n;
 for(int i=1;i<=n;i++)
 
 std::cout<<" 进程 ID ："; std::cin>>id;
 for(int j=i-1;j<=n;j++)
 
 while(id==pcb[j].ID)
 
 std::cout<<" 进程 ID 已存在 "<<std::endl;
 std::cout<<" 进程 ID ："; std::cin>>id;
 
 
 std::cout<<" 进程名： ";
 std::cin>>name;
 std::cout<<" 运行时间： ";
 std::cin>>time;
 std::cout<<" 优先级： ";
 std::cin>>priority;
 n++;// 保存当前就绪进程数
 strcpy(pcb[n].NAME,name);
 pcb[n].ID =id;
 pcb[n].TIME =time;
 pcb[n].PRIORITY =priority;
 p=new QNode;// 插入就绪队列
 p->data=n;
 p->next=NULL;
 Ready.rear->next=p;
 Ready.rear=p;
 


 for(int i=1;i<=n;i++)// 按优先级排队
 
 for(int j=i+1;j<=n;j++)
 if(pcb[i].PRIORITY<pcb[j].PRIORITY)
 
 pcb[0]=pcb[i];
 pcb[i]=pcb[j];
 pcb[j]=pcb[0];
 
 
 menu();
 
 void kill(int n)// 进程终止
 
 long id;
 QNode *p,*q;
 std::cout<<" 请输入要终止的进程 ID:";
 std::cin>>id;
 p=Ready.front->next;
 if(p==NULL)
 std::cout<<" 就绪进程为空！ ";
 while(p!=NULL)
 
 if(id==pcb[n].ID)// 终止进程是队列最后一个
 
 if(n==1) // 队列中只有一个进程，且是终止进程
 
 q=new QNode;
 q->data=Ready.rear->data;
 Empty.rear->next=p;
 Empty.rear=p;
 Ready.front =Ready.rear;
 Ready.front ->next =NULL;
 n--;
 std::cout<<" 进程已终止！ ";
 break;
 
 else //队列中进程多个
 
 while(p!=NULL)
 
 if(p->next->next ==NULL)
 
 q=new QNode;
 q->data=Ready.rear->data;
 Empty.rear->next=p;
 Empty.rear=p;
 p->next =NULL;
 Ready.rear =p;
 n--;
 std::cout<<" 进程已终止！ ";
 break;
 
 p=p->next ;
 
 if(id==pcb[p->data].ID)
 
 if(Ready.front==Ready.rear)
 std::cout<<" 队列为空 !"<< std::endl;
 while(p!=NULL)
 
 pcb[p->data]=pcb[p->data+1];// 修改 PCB 数组里的值
 if(p->next ->next ==NULL)
 
 q=new QNode;
 q->data=Ready.rear->data;
 Empty.rear->next=p;
 Empty.rear=p;
 p->next =NULL;
 Ready.rear =p;
 std::cout<<" 进程已终止！ ";
 break;
 
 p=p->next;
 
 n--;
 break;
 
 p=p->next ;
 
 menu();
 
 void display()
 
 QNode *p;
 p=Ready.front->next;
 std::cout<<"ID"<<" "<<" 名字 "<<" "<<" 运行时间 "<<" "<<" 优先级"<<std::endl;
 while(p!=NULL)
 
 std::cout<<pcb[p->data].ID<<""<<pcb[p->data].NAME<<""<<pcb[p->data].TIME <<""<<pcb[p->data].PRIORITY<<std::endl;
 p=p->next ; 
 menu(); 
 int main()
 
 InitQueue();
 pcb[0].ID =0;
 menu();
 

I see:

void kill();
void exit();

declared at the top of your C++ file when you actually have the code defined as:

void kill(int n)// 进程终止
{
...
...

Change your declaration at the top of your C++ file to match what your code looks like. And whenever you call kill in your code, pass in 1 or whatever you want n to be (e.g. kill(1)).

Also, unlike kill, exit() already exists in C++ and you should remove that declaration from the top of your code and whenever you call it, use something like exit(0).