c++ - 获取错误 : redifinition of bool queue previously declared here

Question

我正在尝试使用 C++ 进行负载平衡。但是出现错误。我已经从 youtube 复制了代码，它在那里工作正常。代码是

//arrayqueue.h

#define QUEUE_H
#pragma once
template <class T>
class queue
{
    public:
        queue()
        {
            size = 5;
            data = new T[size];
            head = 0;
            tail = 0;
        }
        void enqueue (T data);
        T dequeue ();
        T peek ();
        bool isEmpty();

    private:
        T* data;
        int head, tail, size;
        bool needToResize();
        void resize();
};

#include "arrayqueue.cpp"

//arrayqueue.cpp

#ifndef QUEUE_H
#include "arrayqueue.h"
#endif

#include <stdexcept>
using namespace std;

template <class T>
bool queue<T>::needToResize()
{
  return (tail == size);   
}

template <class T>
void queue<T>::resize()
{
    T* temp = new T[2*size];
    for (int i = 0; i < tail - head; i ++)
        temp[i] = data[i+head];
    data = temp;
    tail = tail - head;
    head = 0;
    size *= 2;
}

template <class T>
void queue<T>::enqueue(T obj)
{
    if (needToResize())
        resize();
    data[tail++] = obj;
}

template <class T>
T queue<T>::dequeue()
{
    if (head == tail)
        throw std::out_of_range("Attempt to dequeue from empty queue");
    return data[head++];
}

template <class T>
T queue<T>::peek()
{
    if (head == tail)
        throw std::out_of_range("Attempt to peek from empty queue");
    return data[head];
}

template <class T>
bool queue<T>::isEmpty()
{
    return head == tail;
}

//loadbalancer.h

#define LOADBALANCER_H

#ifndef REQUEST_CPP
#include "request.cpp"
#endif

#include "arrayqueue.h"

class loadbalancer
{
    public:
        loadbalancer()
        {
            systemTime = 0;
        }
        int getTime();
        void incTime();
        void addRequest (request r);
        request getRequest();
        bool isRequestQueueEmpty();
    private:
        int systemTime;
        queue <request> requestQueue;
};
#include "loadbalancer.cpp"

//loadbalancer.cpp

#ifndef LOADBALANCER_H
#include "loadbalancer.h"
#endif

int loadbalancer::getTime()
{
    return systemTime;
}

void loadbalancer::incTime()
{
    systemTime ++;
}

void loadbalancer::addRequest(request r)
{
    requestQueue.enqueue(r);
    incTime();
}

request loadbalancer::getRequest()
{
    incTime();
    if (!requestQueue.isEmpty())
    {
        request r = requestQueue.dequeue();
        return r;
    }
}

bool loadbalancer::isRequestQueueEmpty()
{
    return requestQueue.isEmpty();
}

//request.cpp

#include <string>

#define REQUEST_CPP

using namespace std;

struct request
{
    string source;
    string destination;
    int processTime;
};

//webserver.cpp

#ifndef REQUEST_CPP
#include "request.cpp"
#endif

class webserver
{
    public:
        webserver()
        {
            requestStartTime = 0;
            servername = ' ';
        }
        webserver (char c)
        {
            requestStartTime = 0;
            servername = c;
        }
        void addRequest(request req, int currTime)
        {
            r = req;
            requestStartTime = currTime;
        }
        request getRequest()
        {
            return r;
        }
        char getName()
        {
            return servername;
        }
        bool isRequestDone(int currTime)
        {
            return (currTime >= (requestStartTime + r.processTime));
        }
    private:
        request r;
        int requestStartTime;
        char servername;
};

//loadbalancermain.cpp

#include "request.cpp"
#include "webserver.cpp"
#include "loadbalancer.h"

#include <iostream>
#include <ctime>
#include <cstdlib>
#include <sstream>

using namespace std;

const int NUMWEBSERVERS = 8;

//create a request
request createRandomRequest()
{
    stringstream ips, ipd;
    request r;
    ips << (rand() % 256) << "." << (rand() % 256) << "." << (rand() % 256) << "." << (rand() % 256);
    ipd << (rand() % 256) << "." << (rand() % 256) << "." << (rand() % 256) << "." << (rand() % 256);
    r.source = ips.str();
    r.destination = ipd.str();
    r.processTime = rand()%500;
    return r;
}

int main()
{
    //random number generator
    srand(time(0));
    //create a loadbalancer
    loadbalancer lb;
    //start off with a "full" queue
    for (int i = 0; i < 10; i ++)
    {
        request r = (createRandomRequest());
        lb.addRequest(r);
    }
    //an array of webservers
    webserver webarray[NUMWEBSERVERS];
    for (int i = 0; i < NUMWEBSERVERS; i ++)
    {
        webserver w((char)(i + 65));
        webarray[i] = w;
        webarray[i].addRequest(lb.getRequest(), lb.getTime());
    }
    //loop
    while (lb.getTime() < 10000)
    {
        int currTime = lb.getTime();
        //check each webserver if it's done
        if (webarray[currTime % NUMWEBSERVERS].isRequestDone(currTime))
        {
            request r = webarray[currTime % NUMWEBSERVERS].getRequest();
            cout << "At " << currTime << " " << webarray[currTime % NUMWEBSERVERS].getName() << " processed request from "<< r.source << " to " << r.destination << endl;
            //then give it a new request
            webarray[currTime % NUMWEBSERVERS].addRequest(lb.getRequest(),currTime);
        }

        //every random amt of time, we get a new request
        if (rand() % 20 == 0)
        {
            request r = (createRandomRequest());
            lb.addRequest(r);
        }
        lb.incTime();
    }
}

错误日志如下:

- Filename: C:\Users\Manish Anhal\Desktop\Makefile.win

Processing makefile...
--------
- Makefile Processor: C:\Program Files (x86)\Dev-Cpp\MinGW64\bin\mingw32-make.exe
- Command: mingw32-make.exe -f "C:\Users\Manish Anhal\Desktop\Makefile.win" all

g++.exe -c Pdc/arrayqueue.cpp -o Pdc/arrayqueue.o -I"C:/Program Files (x86)/Dev-Cpp/MinGW64/include" -I"C:/Program Files (x86)/Dev-Cpp/MinGW64/x86_64-w64-mingw32/include" -I"C:/Program Files (x86)/Dev-Cpp/MinGW64/lib/gcc/x86_64-w64-mingw32/4.9.2/include" -I"C:/Program Files (x86)/Dev-Cpp/MinGW64/lib/gcc/x86_64-w64-mingw32/4.9.2/include/c++" 

Pdc/arrayqueue.cpp:11:6: error: redefinition of 'bool queue<T>::needToResize()'
 bool queue<T>::needToResize()
      ^

In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:11:6: note: 'bool queue<T>::needToResize()' previously declared here
 bool queue<T>::needToResize()
      ^
Pdc/arrayqueue.cpp:17:6: error: redefinition of 'void queue<T>::resize()'
 void queue<T>::resize()
      ^
In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:17:6: note: 'void queue<T>::resize()' previously declared here
 void queue<T>::resize()
      ^
Pdc/arrayqueue.cpp:29:6: error: redefinition of 'void queue<T>::enqueue(T)'
 void queue<T>::enqueue(T obj)
      ^
In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:29:6: note: 'void queue<T>::enqueue(T)' previously declared here
 void queue<T>::enqueue(T obj)
      ^
Pdc/arrayqueue.cpp:37:3: error: redefinition of 'T queue<T>::dequeue()'
 T queue<T>::dequeue()
   ^
In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:37:3: note: 'T queue<T>::dequeue()' previously declared here
 T queue<T>::dequeue()
   ^
Pdc/arrayqueue.cpp:45:3: error: redefinition of 'T queue<T>::peek()'
 T queue<T>::peek()
   ^
In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:45:3: note: 'T queue<T>::peek()' previously declared here
 T queue<T>::peek()
   ^
Pdc/arrayqueue.cpp:53:6: error: redefinition of 'bool queue<T>::isEmpty()'
 bool queue<T>::isEmpty()
      ^
In file included from C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.h:28:0:
C:\Users\Manish Anhal\Desktop\Pdc\arrayqueue.cpp:53:6: note: 'bool queue<T>::isEmpty()' previously declared here
 bool queue<T>::isEmpty()
      ^

C:\Users\Manish Anhal\Desktop\Makefile.win:40: recipe for target 'Pdc/arrayqueue.o' failed
mingw32-make.exe: *** [Pdc/arrayqueue.o] Error 1

我做了与此存储库中给出的完全相同的代码拷贝，但无法运行: https://github.com/mistapotta/C-Code/tree/master/C%2B%2B%20Stuff/Unit%206%20-%20arrayqueue/Day%203%264%20-%20Complicated%20Problem

请帮我找到解决方案。

Answer 1

问题是您将 arrayqueue.cpp 构建为单独的翻译单元。

当您这样做时，arrayqueue.cpp 将#include "arrayqueue.h" #include "arrayqueue.cpp"。

这意味着源文件 arrayqueue.cpp source 中的所有函数将被定义两次。

不要构建arrayqueue.cpp。