Why am I getting an error when using vfork()?

Question

This is my code... I don't know why I'm get an error segment... could somebody explain the reason to me?

#include <iostream>

#include <string>

// Required by for routine
#include <sys/types.h>
#include <unistd.h>

using namespace std;


int globalVariable = 2;

main()
{
   string sIdentifier;
   int    iStackVariable = 20;

   pid_t pID = vfork();
   if (pID == 0)                // child
   {
      // Code only executed by child process

      sIdentifier = "Child Process: ";
      globalVariable++;
      iStackVariable++;
      cout << "PROCESO NUMERO"<<getpid()<<sIdentifier;
//          printf("Proceso hijo: PID %d - PPID %d\n", getpid(), getppid());
      cout << " Global variable: " << globalVariable;
      cout << " Stack variable: "  << iStackVariable << endl;
      return (0);
    }
    else if (pID < 0)            // failed to fork
    {
        cerr << "Failed to fork" << endl;
        return (1);
        // Throw exception
    }
    else                                   // parent
    {
      // Code only executed by parent process

      sIdentifier = "Parent Process:";
    }

    // executed only by parent

    cout << sIdentifier;
    cout << " Global variable: " << globalVariable;
    cout << " Stack variable: "  << iStackVariable << endl;
    return (0);
}

Answer 1

Is this of use ? Note the caveats surrounding modification of variables.

The vfork() function has the same effect as fork(), except that the behaviour is undefined if the process created by vfork() either modifies any data other than a variable of type pid_t used to store the return value from vfork(), or returns from the function in which vfork() was called, or calls any other function before successfully calling _exit() or one of the exec family of functions.

Answer 2

If you vfork() both processes are sharing an address space. You should probably only use vfork() if you are going to exec another process pretty much immediately in the child. The reason the system call was created was to avoid the overhead of copying every page in the parent process's address space only to have all those mappings discarded when the child exec's. For your case, use fork() instead.