Question

我目前正在处理一个处于早期阶段的虚拟运行时环境程序，由于使用我的makefile时出现链接器错误，我无法继续工作，如下所示。我收到的错误是：

g++ controller.o processor.o test.o -o final
controller.o: In function `Controller::run()':
controller.cpp:(.text+0x1e0): undefined reference to
Processor::codeParams(char)'
controller.o: In function `Controller::fetch()':
controller.cpp:(.text+0x290): undefined reference to `Controller::pc'
controller.cpp:(.text+0x299): undefined reference to `Controller::pc'
collect2: error: ld returned 1 exit status
makefile:16: recipe for target 'final' failed
make: *** [final] Error 1

我不确定为什么我会收到此错误，因为我认为我已经在与标题对应的源文件中定义了这些内容。下面将给出所有文件，以便编译程序。

TEST.CPP：

#include <iostream>
#include <vector>
#include "includes/controller.h"

using namespace std;

int main()
{
    vector<char> prog = {0x0};

    Controller contr(prog);
    cout << "Error Code: " << contr.run() << endl;

    return 0;
}

controller.cpp：

/*
    Author(s):  James Dolan
    File:       controller.cpp
    Build:      0.0.0
    Header:     includes/controller.h
    DoLR:       21:39 11/1/2017

    Todo: n/a
*/



#include "includes/controller.h"


Controller::Controller(vector<char> prog)
{
    printf("Program:");                         //Display program
    for(auto i : program)
    {
        printf("%02X", i);
    }
    printf("\n");

    Controller::program = program;
}

Controller::~Controller ()
{
}

int Controller::run()
{
    bool runFlag = true;
    int errorCode = 0;
    char curCode;
    vector<char> curInstr;
    int paramRef;

    while(runFlag)
    {
        curCode = fetch();
        printf("curCode:%02X\n", curCode);
        curInstr.push_back(curCode);
        paramRef = proc.codeParams(curCode);

        if (paramRef == 0xffff){runFlag = false; continue;}     //Check if shutdown signal was returned, if so shutdown
        printf("opcode good\n");

        for(int i; i<paramRef; i++){curInstr.push_back(fetch());}
    }


    return errorCode;
}

char Controller::fetch()
{
    return program[pc++];                       //Return next instruction then increment the program counter
}

或者Controller.h：

/*
    Author(s):  James Dolan
    File:       controller.h
    Source:     ../controller.cpp
    DoLR:       21:39 11/1/2017

    Todo: n/a
*/


#ifndef CONTROLLER_H
#define CONTROLLER_H

#include <iostream>
#include <vector>
#include <cstdlib>

#include "processor.h"

using namespace std;

class Controller{

    public:
        Controller(vector<char> prog);
        ~Controller();
        int run();

    protected:

    private:
        vector<char> program;
        static int pc;
        char fetch();
        Processor proc();


};

#endif

processor.cpp：

#include "includes/processor.h"

Processor::Processor()
{
}

Processor::~Processor()
{
}

int codeParams(char code)
{

    switch(code)
    {
        case 0x0:                   //Halt
            return 0;
        default:
            printf("[ERROR!] Invalid opcode [%02X]", code);
            return 0xffff;          //Return shutdown signal
    }
}

processor.h：

#ifndef PROCESSOR_H
#define PROCESSOR_H

#include <iostream>
#include <cstdlib>

class Processor{

    public:
        Processor();
        ~Processor();
        int codeParams(char code);

    protected:

    private:

};

#endif

所有这些都得到了大量的赞赏，因为它将帮助我继续热衷于开发像java vm这样的完全成熟的开源虚拟运行环境，感谢您的时间。

Answer 1

对于成员函数Processor::codeParams，您应将其定义为：

int Processor::codeParams(char code)
//  ~~~~~~~~~~~
{
  ...
}

否则它只是一个普通的（非成员）功能。

对于静态成员Controller::pc，您应该在controller.cpp中的类定义之外定义它。

// Controller.h
class Controller {
    ...
    private:
        static int pc;
};

// controller.cpp
int Controller::pc;

Answer 2

在Controller.cpp中，您需要int Controller::pc = 0;或int Processor::codeParams(char code)

在头文件中，您声明了一个名为pc的静态int，它存在于某处。它需要实际存在于某个地方的转换单元中（在本例中为Controller.cpp），以便当链接器试图找到它时......它就存在了。

在Processor.cpp中，您的签名应该看起来像// add CORS filter $behaviors['corsFilter'] = [ 'class' => Cors::className(), 'cors' => [ // restrict access to 'Origin' => ['*'], 'Access-Control-Request-Method' => ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS'], // Allow only POST and PUT methods 'Access-Control-Request-Headers' => ['*'], // Allow only headers 'X-Wsse' 'Access-Control-Allow-Credentials' => true, // Allow OPTIONS caching 'Access-Control-Max-Age' => 86400, // Allow the X-Pagination-Current-Page header to be exposed to the browser. 'Access-Control-Expose-Headers' => [], ];`，让编译器知道这是处理器的codeParams而不是一个名为codeParams的随机函数，它恰好也会占用一个字符。

G ++ - 未定义对已定义的成员函数的引用

2 个答案: