分段故障（核心已转储）

Question

I have 3 files namely concat.cpp, concat.h and test4concat.cpp, when i compile and execute i get the following error.
Enter the number of splits: 1 Segmentation fault (core dumped)

It asks for the first split and then stops, since i am fairly new to cpp i would need some help on this. Thanks

Following are the 3 file

concat.cpp

#include <iostream>                 
#include <cstring>                  
#include <fstream>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "concat.h"


using namespace std;



char concat(char* si,char* w,char* fid)
{


    strcat (si,w);

    strcat (si,fid);

     return 0;
}

concat.h

#ifndef TRY_H_INCLUDED
#define TRY_H_INCLUDED

char concat(char* si,char* w,char* fid);


#endif

test4concat.cpp

#include <iostream>                 
#include <cstring>                  
#include <fstream>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <concat.h>
using namespace std;


int main ()
 {
 char* si;
 char* w;
 char* fid;


cout << "Enter the number of splits: ";
cin >> si;
cout << "Enter the number of watchdogs: ";
cin >> w;
cout << "Enter the Fid: ";
cin >> fid;
concat(si, w, fid);
cout<<"\nThe string is "<< si <<endl;


}

Problem which i am encountering:

Enter the number of splits: 1 Segmentation fault (core dumped)

Answer 1

You need to allocate memory using malloc (or new as you are writing in C++) before reading data into si, w and fid.

si = new char[10];
w = new char[10];
fid = new char[10];

Of course you need to modify the sizes of the character arrays for your own requirements.

Answer 2

This would be a way to do it in C++, avoiding all manual memory allocation pitfalls:

#include <iostream>                 
#include <string>                  

int main ()
{
  std::string si, w, fid;

  std::cout << "Enter the number of splits: ";
  std::cin >> si;
  std::cout << "Enter the number of watchdogs: ";
  std::cin >> w;
  std::cout << "Enter the Fid: ";
  std::cin >> fid;
  si += w;
  si += fid;
  std::cout<<"\nThe string is "<< si << std::endl;

}

Answer 3

"Enter the number of splits: ";

So you want a number, int .

int si;
cout << "Enter the number of splits: ";
cin >> si;

If you really want to read through pointer, first allocate memory to it with operator new :

int main() {
    char* pt = new char;
    cin >> pt;
    cout << (*pt);
    delete pt;
    return 0;
}

---

C++

There is a std::string class being a C++ string of characters, a specialization of std::basic_string with char as a template parameter. It is flexible and may be used in this case as well:

#include <iostream>                 
#include <string>                  

int main ()
{
  std::string si, w, fid;

  std::cout << "Enter the number of splits: ";
  std::cin >> si;
  std::cout << "Enter the number of watchdogs: ";
  std::cin >> w;
  std::cout << "Enter the Fid: ";
  std::cin >> fid;
  si += w;
  si += fid;

  std::cout<<"\nThe string is "<< si << std::endl;

  return 0;
}