exception种构造函数没有参数，那what成员函数返回什么字符串

exception类构造函数没有参数，那what成员函数返回什么字符串
继承exception时，需要传给exception一个字符串，会与形参不匹配。
并且是不是不能用string？
我的代码如下：
#ifndef MYEXCEPTION_H
#define MYEXCEPTION_H
#include <exception>
#include <iostream>
#include <string>
using namespace std;

class MyException:public exception
{
  public:
  MyException(const char *):exception(const char * ){}; virtual ~MyException() throw (); //编译报错 expected primary -expression before const 这是为什么呢
  protected:
  private:
};

class OMarkError:public MyException
{
  public:
  OMarkError():MyException("mark shuold be between 0 and 100."){}
};

class EMarkError:public MyException
{
  public:
  EMarkError():MyException("grade shuold be between A and E."){}
};

class MonthError:public MyException
{
  public:
  MonthError():MyException("Month shuold be between 1 and 12."){}
};

class DayError:public MyException
{
  public:
  DayError():MyException("Day error."){}
};

class ScriptError:public MyException
{
  public:
  ScriptError():MyException("script exceed."){}
};
#endif // MYEXCEPTION_H


------解决方案--------------------

C/C++ code

class MyException:public exception
{
public:
    MyException(const char *str):exception(str){}
    virtual ~MyException() throw (); //编译报错 expected primary -expression before const 这是为什么呢
protected:
private:
};