c++ - Code giving SEG FAULT only when the class is being derived! -

unable find out bug in below code had written[not purpose though].

  #include < iostream > #include < cstdlib >  using namespace std;   class base{ public:         base(){cout << "base class constructor" << endl;}         void funv() {};         ~base(){cout << "base class destructor" << endl;} ; };  class derived:public base{ public:         char *ch;         derived():ch(new char[6]()){}         ~derived(){                 cout << "before" << endl;                 delete [] ch;                 ch = null;                 cout << "after" << endl;         } };  int main(){          derived * ptr = new derived;          //memcpy(ptr -> ch,"ar\0",4); // works when class derived derved base , when not derived base          ptr -> ch = const_cast < char* >("ar0");  // works when class derived not derived class base          cout << ptr -> ch[1] << endl;          ptr -> funv();          delete ptr;          return 0; }   

have commented on suspected lines of code.

using sun studio 12.

this undefined behavior. cause problem in case, whether derive or not. when assign const char* char* below:

ptr -> ch = const_cast < char* >("ar0"); 

that means, assigning character string defined in non-heap segment (mostly in data segment). 1 should delete memory allocated on heap segment.

also, above assignment statement executed, leak memory pointed ch earlier. 1 way avoid such problem declare variable as,

private: char* const ch; 

as try assigning ch, give compilation error. make write wrapper assign ch , there can take care of deallocation.