Where does the swap space reside?

Consider Peterson’s algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below.

 Repeat 
     flag[i]=true; 
     turn=j; 
     while (P) do no-op; 
     Enter critical section, perform actions, then 
     exit critical section 
     Flag[i]=false; 
     Perform other non-critical section actions. 
 Until false;

For the program to guarantee mutual exclusion, the predicate P in the while loop should be

Consider the following three C functions:

[P1] int*g(void)
     {
       int x=10;
       return(&x);
     }

[P2] int*g(void)
      {
        int *px;
       *px = 10;
        return px;
      }

[P3] int*g(void)
     {
       int *px
       px =(int*)malloc (size of (int));
       *px = 10;
       return px;
     }

Which of the above three functions are likely to cause problems with pointers?

Consider the following C program:

void abc(char *s)
{
   if(s[0]=='\0') return;
   abc(s+1);
   abc(s+1);
   printf("%c",s[0]);
}
main()
{ 
   abc("123");
}

(a) What will be the output of the program?
(b) If abc(s) is called with a null-terminated string s of length n characters (not counting the null ('\0') character), how many characters will be printed by abc(s)?