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#ifndef _CSTR_H
#define _CSTR_H
class CStr
{
public:
    CStr(char *str = NULL);
    ~CStr();
protected:
private:
    char *m_str;
};
#endif;

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error C2065: 'NULL' : undeclared identifier
error C2440: 'default argument' : cannot convert from 'int' to 'char *'
unable to recover from previous error(s);

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CStr::CStr(char *str /* = NULL */)
{
    m_str = str;
}

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#include"iostream.h"
#ifndef _CSTR_H
#define _CSTR_H

class CStr
{
public:
    CStr(char *str);
    ~CStr();
protected:
private:
    char *m_str;
};

CStr::CStr(char *str)//ÕâÀï¿ÉÒÔÓÃchar *str=NULL
{
    m_str=str;
}
CStr::~CStr()
{
    cout<<m_str<<endl;
}
#endif
main()
{   char s[]={"aasdsdfdsf"};
    CStr *c1;
    c1=new CStr(s);
    delete c1;

}
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CStr(char *str);
Õâ¸ö¹¹Ô캯Êý£¬Èç¹ûÎÒ¶¨Òå¸ö¶ÔÏó±ÈÈçCStr cstr;
ÕâÑù¾Í³öÎÊÌâÁË£ºno appropriate default constructor available