未定义的引用c ++,不寻常的情况

Question

我正在用c ++创建一个队列类,但是在使用makefile进行编译时遇到了问题.我的queue.cpp类在这里

#include "queue.h"
#include <stdlib.h>

queue::queue()
{
   front_p = NULL;
   back_p = NULL;
   current_size = 0;
}

void queue::enqueue(int item)
{
    node newnode = node(item, NULL);
   if (front_p == NULL) //queue is empty
    {
       front_p = &newnode;
       back_p = &newnode;
    }
   else 
   {
       back_p->next = &newnode;
       back_p = &newnode;
   }
   current_size ++;
}

我的头文件(queue.h)在这里

class queue
{
  public:
    queue(); // constructor - constructs a new empty queue.
    void enqueue( int item ); // enqueues item.
    int dequeue();  // dequeues the front item.
    int front();   // returns the front item without dequeuing it.
    bool empty();  // true iff the queue contains no items.
    int size();  // the current number of items in the queue.
    int remove(int item); // removes all occurrances of item 
      // from the queue, returning the number removed.

  private:
    class node  // node type for the linked list 
    {
       public:
           node(int new_data, node * next_node ){
              data = new_data ;
              next = next_node ;
           }
           int data ;
           node * next ;
    };

    node* front_p ;
    node* back_p ;
    int current_size ; // current number of elements in the queue.
};

测试程序(tester.cpp)

#include <iostream>
#include "queue.h"
#include <stdlib.h>
using namespace std;

int main(int argc, char * const argv[])
{
    cout << "Lalalalala" << endl;
    queue q1;
    q1.enqueue(5);
}

生成文件

all: tester

tester: queue.o
    g++ -o tester tester.cpp

queue.o: queue.cpp queue.h
    g++ -c queue.cpp

clean:
    rm -f tester *.o

当我输入"make"或"make all"时,我收到此错误:

g++ -o tester tester.cpp
/tmp/ccTOKLWU.o: In function `main':
tester.cpp:(.text+0x33): undefined reference to `queue::queue()'
tester.cpp:(.text+0x44): undefined reference to `queue::enqueue(int)'
collect2: ld returned 1 exit status
make: *** [tester] Error 1

关于它的不寻常之处在于,当在Windows机器上的visual studio中编译时,没有错误.我不知道为什么它不应该像我这样在linux机器上编译.有人会好心解释吗？

Answer 1

你的makefile不正确 - 它tester.cpp依赖于编译queue.o,但根本没有链接queue.o.这就是为什么tester.cpp在未解决的参考文献中汇编结果的原因.

您应该更改您的make文件,如下所示:

all: tester

tester: queue.o tester.o
    g++ queue.o tester.o -o tester

tester.o: tester.cpp tester.h
    g++ -c tester.cpp

queue.o: queue.cpp queue.h
    g++ -c queue.cpp

clean:
    rm -f tester *.o