error LNK2019: unresolved external symbol _vfork referenced in function _main

Question

My Goal is to get outputs from Critical Section C Program (Visual Studio 2013 on Windows 7). I get the following errors:

error LNK2019: unresolved external symbol _vfork referenced in function _main
error LNK1120: 2 unresolved externals

My Code is

#include<stdio.h>
#include<sys/types.h>
#include<stdlib.h>
int turn;
int flag[2];
int main(void)
{
    int pid, parent = 1;
    printf("before vfork\n");
    if ((pid = vfork())<0)
    {
        perror("vfork error\n");
        return 1;

    }
    while (1)
    {
        if (pid == 0)
        {
            while (parent == 1)
            {
                sleep(2);
            }
            parent = 0;
            flag[0] = 1;
            turn = 1;
            while (flag[1] && turn == 1);
            printf("This is critical section:parent process\n");
            flag[0] = 0;
        }
        else
        {
            parent = 2;
            printf("This is parent");
            flag[1] = 1;
            turn = 0;
            while (flag[0] && turn == 0);
            printf("This is critical section:child process %d \n", pid);
            flag[1] = 0;
        }
    }

}

Answer 1

Windows does not implement the vfork() system call; it is generally only available on UNIX systems. You will need to use threads to implement equivalent functionality.

Information on using threads in Windows is available in the Windows Dev Center under " Processes and Threads ".

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Please note that, as written, your program invokes undefined behavior . The POSIX.1 specification explains that:

…behavior 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(2) or one of the exec(3) family of functions.

To make a long story short, you can only use vfork() to lead up to an exec() . It cannot safely be used for anything else at all.