why the following code using char* doesn't work?

[indiocolifa]

why the following code doesn't work (gives me a general protection fault):

int    MAX = 200;
char *optiondesc[MAX];

int main()
{
  ...

   // get maximum number of options
    
    do
    {
        cout << "Enter the number of options you want to evaluate:" << endl
            << "(minimum is 2)" << endl;
        cout << "?";
        
        cin >> numopt;
    } while (numopt < 2);
    
	for (i=0; i < numopt; i++)
	{
		cout << "Option " << i << "?";
		cin >> optiondesc[i];
	}
...
return 0;
}

May be I've not allocated spacE?

[vinodp]

May be I've not allocated spacE?
-----------------------------------------------------------
YES ur right u have not allocated the space for char*
try something like this
for (i=0; i <MAX ; i++)
{
optiondesc[i]=(char*)malloc(size);

}


Vinod

[stober]

since you are using C++, why not use the vector and get rid of the malloc() stuff

#pragma warning(disable : 4786)
#include <stdio.h>
#include <string>
#include <vector>
#include <iostream>
using namespace std;


vector<string> optiondesc;

int main()
{

   // get maximum number of options
    string option;
	int numopt, i;
    do
    {
        cout << "Enter the number of options you want to evaluate:" << endl
            << "(minimum is 2)" << endl;
        cout << "?";
        
        cin >> numopt;
    } while (numopt < 2);
    
	for (i=0; i < numopt; i++)
	{
		cout << "Option " << i << "?";
		cin >> option;
		optiondesc.push_back(option);
	}

return 0;
}

[Cheesus]

The real reason your original code didn't work was in the declaration of 'optiondesc'.

By declaring it as:

char *optiondesc[MAX];

you are saying you want and array of MAX elements where each element is of type char*.

That's why you need to inialise each element to point to some memory.
This could also have been done as:

char optiondesc[MAX][256];

(note the abscence of the * in the declaration!)

Where each element would have been statically allocated 256 bytes.

While this is legitimate I totally agree with the other guys responses, but just thought someone should clear it up for you as to why your original code didn't work.