Hello friends,

I am trying to use const char* as the primary key of map. But since contents pointed by pointer can change any time, map's primary key is becoming null.
The following program demonstates my problem. Is there anyway to replace assignment of primary key with strcpy? Also, I understand that this problem can be solved by writing a wrapper class for pointer. But I want to know whether STL provides any way to resolve this problem:

Program :

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<vector>
#include<map>
using namespace std;
struct ltstr
{
  bool operator()(const char* s1, const char* s2) const
  {
    return strcmp(s1, s2) ;
  }
};

main()
{
        map<const char*, int,ltstr> map_v;
        char testt[20] = {"first"};
        map_v.insert(map<const char*, int, ltstr>::value_type(testt, 1));
        map_v.insert(map<const char*, int, ltstr>::value_type("second", 2));
        map_v.insert(map<const char*, int, ltstr>::value_type("third", 3));

        cout<< "List of Elements of map" << endl;
        cout<< "size = "<< map_v.size()<<endl;
        map<const char*, int, ltstr> ::iterator itr;
        for(itr=map_v.begin(); itr!=map_v.end(); itr++)
        {
                 cout<< itr->first<< ","<< itr->second<<endl;
        }

        cout <<endl <<endl;

        cout<< "Before assigning test string to NULL" <<endl;
        itr = map_v.find("first");
        if(itr != map_v.end())
        {
                cout<< "Element found" <<endl;
                cout<< itr->second<< ","<< itr->second<<endl;
        }
        else
        {
                cout<< "Element not found" <<endl;
        }

        cout <<endl <<endl;
        memset(testt , '\0', sizeof(testt));
        cout<< "After assigning test string to NULL" <<endl;
        itr = map_v.find("first");
        if(itr != map_v.end())
        {
                cout<< "Element found" <<endl;
                cout<< itr->second<< ","<< itr->second<<endl;
        }
        else
        {
                cout<< "Element not found" <<endl;
        }
}

Output:

List of Elements of map
size = 3
third,3
second,2
first,1


Before assigning test string to NULL
Element found
1,1


After assigning test string to NULL
Element not found