c++ - gcc 4.7.4 链接问题 : Undefined Symbols for Architecture x86_64

Question

我是新来的，所以我希望你能帮助我。我在一个 C++ 项目中工作，试图用终端 (Mac Os) 编译它，但是当我包含我的类的 .hpp 时我总是得到一个错误，但是当我包含 .cpp 时却没有。

I tried to make the simplest example in the main to see more clearly the issue.

这些是我的文件:

main.cpp

#include "Point.hpp"

int main(){
  Point p1;
}

点.hpp

#ifndef Point_hpp
#define Point_hpp

#include <math.h>
#include <iostream>
#include <stdio.h>

class Point{
private:
  double dX;
  double dY;

public:
  Point();
  Point(double dX, double dY);

  void setX(double dX);
  double getX();
  void setY(double dY);
  double getY();

  double getDistance(Point p);

  void move(double dDespX, double dDespY);

  void display();
};

#endif

点.cpp

#include "Point.hpp"

Point::Point(){
  dX = 0;
  dY = 0;
}

Point::Point(double dX, double dY){
  this -> dX = dX;
  this -> dY = dY;
}

void Point::setX(double dX){
  this -> dX = dX;
}

double Point::getX(){
  return dX;
}

void Point::setY(double dY){
  this -> dY = dY;
}

double Point::getY(){
  return dY;
}

double Point::getDistance(Point p){
  double dDist;
  dDist = sqrt(pow(p.dX - dX, 2) + pow(p.dY - dY, 2));
  return dDist;
}

void Point::move(double dDespX, double dDespY){
  dX += dDespX;
  dY += dDespY;
}

void Point::display(){
  std::cout << "Point = (" << dX << "," << dY <<")" << std::endl;
}

当我尝试编译(使用'make main')时，我从终端得到这个:

$ make main
c++     main.cpp   -o main
Undefined symbols for architecture x86_64:
  "Point::Point()", referenced from:
      _main in ccVzh5gg.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make: *** [main] Error 1

Answer 1

您需要将Point.cpp 添加到您在makefile 中编译和链接的文件列表中。所以将编译行更改为

c++     main.cpp  Point.cpp  -o main

因为您没有将 Point.cpp 文件中的定义链接到可执行文件，所以您无权访问 Point.cpp 中提供的函数，您只能在编译时知道它们的声明(参数和返回值)。