Question

class Base {

    protected:
            string m_strName;
            char* pchChar;
    public:
            Base()
            {
                    m_strName = "Base";
                    pchChar   = NULL;
            };

           void display()
            {
                    printf(" display name : %s %c\n",m_strName.c_str(),pchChar);
             };
  };

 class Derived : protected Base {
       public:
               Derived()
               {
                       init();
               };

            void init()
            {
                    m_strName = "Derived";
                    pchChar = (char*)malloc(sizeof(char));
                    strcpy(pchChar,"A");
                    printf(" char %c\n",*pchChar);
                    display();
            };
};

int main()
{
        Derived* pDerived = new Derived();
        return 0;
}

The observed output is

    char A
    display name : Derived P

whereas i expected pchChar should have value “A” on both occasions.
am i missing any piece of information??
pls suggest.

Answer 1

You forgot *:

printf(" display name : %s %c\n",m_strName.c_str(), *pchChar);

It should be *pchChar, not pchChar. Because you’re printing it as %c.

Or you can use %s as format string, and your printf would work, if the c-string is null-terminated string. Currently its not null-terminated. You should be doing this:

pchChar = (char*)malloc( 2 * sizeof(char)); //2 chars, one for `\0`
strcpy(pchChar,"A");

Or even better use new, and std::cout.

Also, don’t forget to call free with malloc to deallocate the memory once you’re done with it. And if you use new, use delete.