c++ - 未定义对 `typeinfo and ' vtable 的引用

Question

我目前正在开发一个使用虚函数用户的程序。我只使用了一个虚拟函数，并且遇到了一个似乎是常见问题的常见解决方案，我已经尝试过但不幸的是没有成功。

我最初有 virtual void calcArea();在 BasicShape.h 中没有任何定义或指定为纯虚函数。我更改了它并在末尾添加了 {}(正如另一个有类似问题的线程所建议的那样)，但我仍然收到以下错误:

我输入:

g++ BasicShape.h BasicShape.cpp circle.h circle.cpp Rectangle.h Rectangle.cpp driver.cpp -o Lab4

然后我得到:

/tmp/ccf1Y4Br.o: In function `BasicShape::BasicShape()': circle.cpp:(.text._ZN10BasicShapeC2Ev[_ZN10BasicShapeC5Ev]+0xf): undefined reference to `vtable for BasicShape'
/tmp/ccf1Y4Br.o:(.rodata._ZTI6circle[_ZTI6circle]+0x10): undefined reference to `typeinfo for BasicShape'
/tmp/ccc7gjtH.o:(.rodata._ZTI9Rectangle[_ZTI9Rectangle]+0x10): undefined reference to `typeinfo for BasicShape'
collect2: error: ld returned 1 exit status

有什么想法吗？

这是实现文件BasicShape.h:

#ifndef BASICSHAPE_H
#define BASICSHAPE_H

class BasicShape 
{
  protected: 
    double area;

  public:
    double getArea() const;
     virtual void calcArea();
};

#endif

随附的 BasicShape.cpp 文件:

#include "BasicShape.h"

double BasicShape::getArea() const
{
  return area;
}

void BasicShape::calcArea()
{
}

圆.h:

#include "BasicShape.h"

#ifndef CIRCLE_H
#define CIRCLE_H

class circle : public BasicShape
{
  private:
    long centerX;
    long centerY;
    double radius;

  public:
    circle(long, long, double);
    long getCenterX() const;
    long getCenterY() const;
    virtual void calcArea();
};

#endif

圆.cpp:

#include "circle.h"

// constructor
circle::circle(long userIn, long userIn2, double userIn3)
{
  centerX = userIn;
  centerY = userIn2;
  radius = userIn3;
  calcArea();
}

// accesors
long circle::getCenterX() const
{
  return centerX;
}

long circle::getCenterY() const
{
  return centerY;
}

// virtual function
void circle::calcArea()
{
  area = (3.14159 * radius * radius);
}

矩形.h

#include "BasicShape.h"

#ifndef RECTANGLE_H
#define RECTANGLE_H

class Rectangle : public BasicShape
{
  private:
    long width;
    long length;

  public:
    Rectangle(long, long);
    long getWidth() const;
    long getLength() const;
    virtual void calcArea();
};

#endif

矩形.cpp:

#include "Rectangle.h"

// constructor
Rectangle::Rectangle(long userIn, long userIn2)
{
  width = userIn;
  length = userIn2;
  calcArea();
}

// accessors
long Rectangle::getWidth() const
{
  return width;
}

long Rectangle::getLength() const
{
  return length;
}

void Rectangle::calcArea()
{
  area = (length * width);
}

驱动程序不完整，但无论如何与我的问题无关(至少我是这么认为的)。

#include <cassert>
#include <iostream>
#include "BasicShape.h"
#include "Rectangle.h"
#include "circle.h"
using namespace std;

int main()
{

  cout << "Testing the functionality and efficiency of the circle class...\n";
  // declare circle object and test accessors and area computation
  circle objCircle(8,8,4);
  assert(objCircle.getCenterX() == 8);
  assert(objCircle.getCenterY() == 8);
  assert(objCircle.getArea() == 50.26544);
  cout << "Circle object testing completed successfully\n";

  cout << "Testing the functionality and efficiency of the Rectangle class...\n";
  // declare rectangle object and test accessors and area computation  
  //Rectangle objRec();

  return 0;
}

Answer 1

实际上，正如所指出的，您不必编译 header 。 (虽然你可以，但在这里无关紧要——gcc 将生成预编译头文件)。

更有趣的是:您的示例在这里完美运行，GCC 4.6.3。

此外，旁注:calcArea 不应公开