conversion string to character in c++ Not Working Properly - c++

Question

make a function which receive the file name but it not working properly because it receives "Doctor.txtG" but I am giving "Doctor.txt" how can i resolve it?My code is Given below......
#include <iostream>
#include <conio.h>
#include <fstream>
using namespace std;
int number_of_lines = 0;
int numberoflines(string A);
int main()
{
cout<<numberoflines("Doctor.txt");
getch();
return 0;
}
int numberoflines(string A)
{
int Len;
char Chr[Len];
Len=A.length();
A.copy(Chr, Len);
//cout<<Len;
cout<<Chr;
string line;
ifstream myfile(Chr);
if(myfile.is_open())
{
while(!myfile.eof())
{
getline(myfile,line);
number_of_lines++;
}
myfile.close();
}
return number_of_lines;
}

Answer 1

It needs to copy a null-terminated byte into Chr.
Use
strcpy(Chr, A.c_str());
instead of A.copy(Chr, Len);
And you should properly init Chr like
char Chr[1024]
or
char* Chr = new char[Len + 1].

Answer 2

Your problem is happening because you are trying to create a char array with the size Len. But you have not initialized Len before using it. This is why it is resulting in undefined behavior and creating this problem. Always try to initialize variables when you declare them. Otherwise, this problem will happen quite often.
However, You don't need to create another char array. Just use std::string::c_str(); in your parameter for the constructor of the ifstream. I am giving a sample code below. This should solve your problem.
#include <iostream>
#include <conio.h>
#include <fstream>
using namespace std;
int number_of_lines = 0;
int numberoflines(string A);
int main()
{
cout<<numberoflines("Doctor.txt");
getch();
return 0;
}
int numberoflines(string A)
{
string line;
ifstream myfile(A.c_str());
if(myfile.is_open())
{
while(!myfile.eof())
{
getline(myfile,line);
number_of_lines++;
}
myfile.close();
}
return number_of_lines;
}