Question

it’s a basic program for array of pointer to objects.

#include <iostream>
using namespace std;

class city
{
protected:
    char *name;
    int len;
public:
    city()
    {
        len=0;
        name= new char[len+1];
    }
    void getname(void)
    {
        char *s;
        s= new char[30];
        cout<< "enter city name";
        cin >> s;
        len= strlen(s);
        name = new char[len+1];
        strcpy(name, s);
    }
    void printname(void)
    {
        cout<< name <<"\n";
    }
};

compiler says problem is in the “cout<< name <<“\n”;”

int main()
{
    city *cptr[10];

    int n=1;
    int option;

    do
    {
        cptr[n]= new city;
        cptr[n]->getname();
        n++;
        cout<< "continue? yes=1, no=0. select now?";
        cin>> option;
    }
    while(option);

    cout<< endl<< endl;
    for (int i=1;i<=n;i++)
    {
        cptr[i]-> printname();
    }

    cin.ignore();
    getchar();
    return 0;
};

There’s also a warning(this warning is not an issue)

warning C4996: 'strcpy': This function or variable may be unsafe. Consider using strcpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files\microsoft visual studio 10.0\vc\include\string.h(105) : see declaration of 'strcpy'

I tried strcpy_s to remove the warning, but the word is unrecognized.

Answer 1

cptr is an array of character pointers. And the size of the array is fixed to 10:

city *cptr[10];

This makes 0 to 9 as the valid index into the array. But your do-while loop does not perform this check. If the user keeps continuing by inputting 1 you’ll go and write beyond the array.

And array index in C++ start with 0 and not 1 so

for (int i=1;i<=n;i++)

should be:

for (int i=0;i<n;i++)

And

int n=1;

should be

int n=0;

Also consider using strncpy in place of strcpy.

Also you are leaking memory by not freeing the memory allocated to s. You need to free it by calling delete:

char *s;
s= new char[30];
// use it
delete[]s;