程序运行出错了

这是本人的一个编程作业题，是一个很简单的程序，编译可以通过，结果也能出现，但是有个严重的错误，因为出现结果的时候，总提示程序运行出错，我就是找不出来，希望哪位达人能指点我一下，感激不尽
//cow.h
#ifndef COW_H_
#define COW_H_

class Cow
{
private:
    char name[20];
    char *hobby;
    double weight;
public:
    Cow();
    Cow(char *nm, char *ho, double wt);
    Cow(const Cow &c);
    ~Cow();
    Cow & operator=(const Cow &c);
    void ShowCow() const;
};
#endif


//////////////////////////////////////////////////
//cow.cpp
#include <iostream>
#include "cow.h"
using namespace std;

//member methods

Cow::Cow()
{
    strcpy(name, "little white");
    
    hobby = new char[20];
    strcpy(hobby, "drink");
    weight=100;
}

Cow::Cow(const Cow &c)
{
    strcpy(name, c.name);
    int len=strlen(c.hobby);
    hobby=new char[len+1];
    strcpy(hobby, c.hobby);
    weight=c.weight;
}

Cow::Cow(char *nm, char *ho, double wt)
{
    strcpy(name, nm);
    int len=strlen(ho);
    hobby=new char[len+1];
    strcpy(hobby, ho);
    wt=weight;
}

Cow::~Cow()
{
    delete [] name;
    delete [] hobby;
}

Cow & Cow::operator =(const Cow &c)
{
    strcpy(name, c.name);
         int len=strlen(c.hobby);
    hobby=new char[len+1];
    std::strcpy(hobby, c.hobby);
    weight=c.weight;
    
    return *this;
}

void Cow::ShowCow() const
{
    cout << "name: " << name << endl;
    cout << "hobby: " << hobby << endl;
    cout << "Weight: " << weight << endl;

}

////////////////////////////////////////////
//usecow.cpp
#include <iostream>
#include "cow.h"
using namespace std;

int main()
{
    Cow cow1;
    Cow cow2("ketty", "eat", 100);
    //Cow cow3(cow2);

    cow1.ShowCow();
    cow2.ShowCow();
    //cow3.ShowCow();

    //Cow cow4=cow3;
    //cow4.ShowCow();

    return 0;
}