Question

我正在努力学习使用C ++进行OOP并遇到问题。我确定它是一个内存分配问题，但似乎无法理解它。任何帮助将不胜感激。

我的客户代码

    #include <iostream>
    #include "Box.cpp"

    using namespace std;

    int main(){
        Box *box = new Box;
        return 0;
    }

我的盒子类......

    #include <iostream>

    using namespace std;

    class Box{

        private:
            double width;
            double height;
            double perimeter;
            double area;


        public:
            Box(){
                cout << "Box created" << endl;
            }

            ~Box(){
                cout << "Box Destroyed" << endl;
            }

            double getWidth(){
                //
                return this->width;
            }

            double getHeight(){
                //
                return this->height;
            }

            double getArea(){
                //
                return this->area;
            }

            double getPerimeter(){
                //
                return this->perimeter;
            }

            void setWidth(double w){
                //
                this->width = w;
                if(!this->height){
                    computeSetArea(this->width, this->height);
                    computeSetPerimeter(this->width, this->height);
                }
            }

            void setHeight(double h){
                //
                this->height = h;
                if(!this->width){
                    computeSetArea(this->width, this->height);
                    computeSetPerimeter(this->width, this->height);
                }
            }

        private:
            void computeSetArea(double w, double h){
                //
                this->area = w*h;
            }

            void computeSetPerimeter(double w, double h){
                //
                this->perimeter = (w * 2) + (h + 2);
            }
    };

我使用gcc并执行：

    gcc Box.cpp client.cpp -o mainfile

之后我收到此错误。

/tmp/ccaVb21k.o: In function `__static_initialization_and_destruction_0(int, int)':
Box.cpp:(.text+0x1d): undefined reference to `std::ios_base::Init::Init()'
Box.cpp:(.text+0x22): undefined reference to `std::ios_base::Init::~Init()'
/tmp/ccaVb21k.o:(.eh_frame+0x12): undefined reference to `__gxx_personality_v0'
/tmp/ccjtbzi4.o: In function `main':
client.cpp:(.text+0x14): undefined reference to `operator new(unsigned int)'
client.cpp:(.text+0x3f): undefined reference to `operator delete(void*)'
/tmp/ccjtbzi4.o: In function `__static_initialization_and_destruction_0(int, int)':
client.cpp:(.text+0x6c): undefined reference to `std::ios_base::Init::Init()'
client.cpp:(.text+0x71): undefined reference to `std::ios_base::Init::~Init()'
/tmp/ccjtbzi4.o: In function `Box::Box()':
client.cpp:(.text._ZN3BoxC1Ev[Box::Box()]+0x11): undefined reference to `std::cout'
client.cpp:(.text._ZN3BoxC1Ev[Box::Box()]+0x16): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
client.cpp:(.text._ZN3BoxC1Ev[Box::Box()]+0x1e): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)'
client.cpp:(.text._ZN3BoxC1Ev[Box::Box()]+0x26): undefined reference to `std::basic_ostream<char, std::char_traits<char> >::operator<<(std::basic_ostream<char, std::char_traits<char> >& (*)(std::basic_ostream<char, std::char_traits<char> >&))'
/tmp/ccjtbzi4.o:(.eh_frame+0x12): undefined reference to `__gxx_personality_v0'
/tmp/ccjtbzi4.o:(.eh_frame+0x4b): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status

Answer 1

你的代码编译得很好，你得到一个链接器错误（ld是链接器，它返回1（错误）），这是抱怨缺少c ++库。

要修复，您需要将stdc ++ lib添加到命令行，或使用g ++。

将gcc替换为g++或将-lstdc++添加到您的gcc命令行。

gcc Box.cpp client.cpp -o mainfile -lstdc++

或

g++ Box.cpp client.cpp -o mainfile

这会将std c ++库与已编译的代码链接起来。使用g++，您可以省略此步骤。

Answer 2

设置这样的类结构对我有用：

Box.h：

class Box
{
public:
    Box();
    ~Box();

    double getWidth();
    double getHeight();
    double getArea();
    double getPerimeter();
    void setWidth(double w);
    void setHeight(double h);
    void computeSetArea(double w, double h);
    void computeSetPerimeter(double w, double h);

private:
    double width;
    double height;
    double perimeter;
    double area;
};

然后是Box.cpp：

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

Box::Box(){
    cout << "Box created" << endl;
}

Box::~Box(){
    cout << "Box Destroyed" << endl;
}

double Box::getWidth(){
    return this->width;
}

double Box::getHeight(){
    return this->height;
}

double Box::getArea(){
    return this->area;
}

double Box::getPerimeter(){
    return this->perimeter;
}

void Box::setWidth(double w){
    this->width = w;
    if(!this->height){
        computeSetArea(this->width, this->height);
        computeSetPerimeter(this->width, this->height);
    }
}

void Box::setHeight(double h){
    this->height = h;
    if(!this->width){
        computeSetArea(this->width, this->height);
        computeSetPerimeter(this->width, this->height);
    }
}

void Box::computeSetArea(double w, double h){
    this->area = w*h;
}

void Box::computeSetPerimeter(double w, double h) {
    this->perimeter = (w * 2) + (h + 2);
}

输出：

Box created

Answer 3

尝试使用g ++代替gcc。

对std :: ios_base :: Init :: Init（）的未定义引用

3 个答案: