Question

From now on, I think after fork() is being called, the local variable is duplicated into parent process and child process, they are separated. But I try to fetch the address of each local variable in different process,it turns out that they are same:

int main(void){
  int local = 10;
  pid_t childPid;
  childPid = fork();
  if(childPid == 0 ){
    printf("[Child] the local value address is %p\n",&local);
  }else if(childPid < 0){
    printf("there is something wrong");
  }else{
    printf("[Parent] the local value address is %p\n",&local);
  }
  return (EXIT_SUCCESS);
}

The output is:

[Parent] the local value address is 0x7fff5277baa8
[Child] the local value address is 0x7fff5277baa8

Any idea about this?

Answer 1

Being in a different “space” means that the “same” index point in different spaces does not refer to the same thing. Think of “spaces” as pieces of paper. “The 4th character of the 3rd line” on page 1 does not refer to the same thing as on page 2.