Consider this C code to swap two integers and these five statements:

void swap(int *px, int *py) 
{ 
    *px = *px - *py; 
    *py = *px + *py; 
    *px = *py - *px; 
}

S1: will generate a compilation error

S2: may generate a segmentation fault at runtime depending on the arguments passed

S3: correctly implements the swap procedure for all input pointers referring to integers stored in memory locations accessible to the process

S4: implements the swap procedure correctly for some but not all valid input pointers

S5: may add or subtract integers and pointers.

Consider the following C program segment:

char p[20];
char *s = "string";
int length = strlen(s);
for(i=0; i < length; i++)
  p[i] = s[length-i];
printf("%s",p);

The output of the program is

Consider the C program shown below.

#include < stdio.h >
#define print(x) printf("%d ", x)
int x;
void Q(int z) {
   z += x; print(z);
}
void P(int *y) {
   int x = *y+2;
   Q(x); *y = x-1;
   print(x);
}
main(void) {
   x = 5;
   P(&x);
   print(x);
}

The output of this program is

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?