Thread: Useless conversion from string to char*

Good afternoon. I tried to translate the warning from portuguese to english.

edit: I figured out

Code:

 
thames@semaht ~/C++ $ g++ -g -Wall inheritance.cpp -o inheritance
inheritance.cpp: Na função membro ‘void Derived1Level1::f(char*)’:
inheritance.cpp:32:21: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:33:21: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp: Na função membro ‘void Derived2Level1::f(char*)’:
inheritance.cpp:48:23: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp: Na função membro ‘void DerivedLevel2::f(char*)’:
inheritance.cpp:59:21: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:60:37: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:61:32: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp: Na função ‘int main()’:
inheritance.cpp:72:17: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:75:19: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:77:19: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:78:19: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:81:18: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
inheritance.cpp:83:9: warning: conversão obsoleta de constante string para ‘char*’ [-Wwrite-strings]
thames@semaht ~/C++ $

Code:

 
#include <iostream> 

using namespace std;

class BaseClass { 
    
  public: 
    BaseClass() {}
    void f(char *s = "unknown")
    { 
      cout << "Function f() in Baseclass called from " << s << endl; 
      h();      
    } 
  protected: 
    void g(char *s = "unknown") 
    { 
      cout << "Function g() in BaseClass called from " << s << endl;           
    } 
  private: 
     void h()
     { 
        cout << "Function h() in BaseClass\n";       
     } 
};      

class Derived1Level1: public virtual BaseClass
{ 
   public: 
     void f(char *s = "unknown")
     { 
        cout << "Function f() in Derived1Level1 called from " << s << endl;
        g("Derived1Level1");
        h("Derived1Level1");  
     }
     
     void h(char *s = "unknown")
     { 
        cout << "Function h() in Derived1Level1 called from " << s << endl;     
     }          
}; 

class Derived2Level1: public virtual BaseClass 
{ 
    public: 
      void f(char *s = "unknown")
      { 
          cout << "Function f() in Derived1Level1 called from " << s << endl; 
          g("Derived2Level1");
          // h() // error: BaseClass::h() is not accessible      
      } 
}; 

class DerivedLevel2: public Derived1Level1, public Derived2Level1
{ 
    public: 
      void f(char *s = "unknown")
      { 
         cout << "Function f() in DerivedLevel2 called from " << s << endl;
         g("DerivedLevel2");
         Derived1Level1::h("DerivedLevel2");
         BaseClass::f("DerivedLevel2");  
      }             
};

int main(void) 
{ 
  BaseClass bc; 
  Derived1Level1 d1l1; 
  Derived2Level1 d2l1; 
  DerivedLevel2  dl2;
  
  bc.f("main(1)");
  // bc.g(); // error:  BaseClass::g() is not accessible
  // bc.h(); // error: BaseClass::h() is not accessible
  d1l1.f("main(2)");
  // d1l1.g(); 
  d1l1.h("main(3)");
  d2l1.f("main(4)");
  // d2l1.g();
  // d2l1.h();
  dl2.f("main(5)");
  // dl2.g();
  dl2.h();
  
  return 0;     
}

Considering the book is using C string literals and without const, no less, I would suggest you be careful with that book. It might be a bad book.
Since I can find no good review on the book (much less so without an author name), the only advice I can give on that part is that you share some examples from different parts of the book so we can say if it's a good book or not. Learning bad examples can be a pain if/when you have to unlearn them later (and would suck big time for you).