#include <stdio.h>

int* f(int x) {

    int *pp;

    if ( x ) {

      int y = 3;
      
      pp = &y; // ok so far

    }

    //y = 4; // does not compile

    // pp is now dangling!
    
    *pp = 7; // Wrong!!! But may not crash!! Sneaky bug

    return pp; // Super wrong!!

}


void g(int *p) { 

    int a = 3;
    int b = 4;

    *p = 123; 

    printf("The value of p is %d\n", *p);

    // *** Check this out, we have overwritten memory! ***
    // *** Very common bug. Watch-out for this type of errors ***
    // Note: this example may not work on all systems
    // It depends where the local variables appear in the 
    // activation record
    printf("The value of a is %d\n", a);
    printf("The value of b is %d\n", b);

}


int main() {

    int *p;

    p = f(3); // p is now dangling too

    *p = 5;   // Wrong! but can also be a silent problem

    printf("The value is %d\n", *p);
    
    // And now the fun part!
    g(p);

    return 0;

}