求指教下面这个代码哪里不对

#include
using namespace std;
class CString
{
public :
CString(char*str);
CString();
~CString();
void Print();
CString(const CString &src);
CString&operator=(const CString &src);
CString operator+(CString r);
friend ostream&operator<<(ostream &output,CString obj);
private:
char *s;
int length;
};

CString::CString(char*str)
{
length=strlen(str);
s=new char[length];
strcpy(s,str);
}
CString::CString()
{
length=10;
s=new char[length];
s[1]=0;
}
CString::~CString()
{
delete [] s;
}
void CString::Print()
{
cout<<s<<endl;
}
CString::CString(const CString &src)
{
if(strlen(src.s)<length)
{strcpy(s,src.s);}
else
{
int m=strlen(src.s)*2;
char *temp=new char[m];
strcpy(temp,src.s);
delete[]s;
s=temp;
}
}

CString& CString::operator=(const CString &src)
{
if(this==&src)
{return*this;}
else
{
if(strlen(src.s)<length)
{strcpy(s,src.s);}
else
{
int m=strlen(src.s)*2;
char *temp=new char[m];
strcpy(temp,src.s);
delete[]s;
s=temp;
}
}
return *this;
}

CString CString::operator+(CString r)
{
CString tem;
int remain=tem.length-length;
if(remain>strlen(r.s))
{
strcpy(tem.s,s);
strcpy(tem.s,r.s);
return tem;
}
else
{
int m=length+strlen(r.s)+1;
char *temp=new char[m];
strcpy(temp,s);
strcpy(temp,r.s);
delete[]tem.s;
tem.s=temp;
return tem;
}
}

ostream& operator<<(ostream &output,CString obj)
{
output<<obj.s<<endl;
return output;
}

int main()
{
CString str1("str1");
str1.Print();

 CString str2("str2");
 str2.Print();

 CString str3;

 str3=str2+str1;
 cout<<str3;
 CString str4=str3;
 cout <<str4;
 system("pause");
 return 0;

}

编译没有问题，运行就出现问题了，哪里不对，看了半边没找出来

同学，bug是调试出来的，不是“看”出来的。我的天。