Dereferencing Raw Pointers

Exercises

Immutable raw pointers

// Fix the code to make it compile. You may not modify any statement.

fn main() {
    let num = 123;
    let ptr = &num as *const i32;
    println!("{} stored at {:p}", *ptr, ptr);
}

fn main() {
  let num = 123;
  let ptr = &num as *const i32;
  unsafe {
      println!("{} stored at {:p}", *ptr, ptr);  
  }
}

Mutable raw pointers

// Fix the code to make it compile.

fn main() {
    // print first 10 fibonacci numbers
    let (mut a, mut b) = (1, 0);
    let mut c = 0;
    let ptr_a = &mut a as *const i32;
    let ptr_b = &mut b as *const i32;
    let ptr_c = &mut c as *const i32;
    for _ in 0..10 {
        *ptr_c = *ptr_a + *ptr_b;
        println!("{}", *ptr_c);
        *ptr_a = *ptr_b;
        *ptr_b = *ptr_c;
    }
}

fn main() {
  // print first 10 fibonacci numbers
  let (mut a, mut b) = (1, 0);
  let mut c = 0;
  let ptr_a = &mut a as *mut i32;
  let ptr_b = &mut b as *mut i32;
  let ptr_c = &mut c as *mut i32;
  unsafe {
      for _ in 0..10 {
          *ptr_c = *ptr_a + *ptr_b;
          println!("{}", *ptr_c);
          *ptr_a = *ptr_b;
          *ptr_b = *ptr_c;
      }
  }
}

Multiple pointers

// Fix the code to make it compile.

macro_rules! ptr {
    ($type:ty, $var:ident) => {
        &mut $var as *mut $type
    };
}

fn main() {
    let mut x = 20;
    let ptr1 = ptr!(i32, x);
    let ptr2 = ptr!(i32, x);
    println!("x: {x}");
    *ptr1 = *ptr1 * 2;
    *ptr2 = *ptr2 * 2;
    *ptr2 = *ptr1 * 2;
    println!("x * 8 = {x}");
}

macro_rules! ptr {
  ($type:ty, $var:ident) => {
      &mut $var as *mut $type
  };
}

fn main() {
  let mut x = 20;
  let ptr1 = ptr!(i32, x);
  let ptr2 = ptr!(i32, x);
  println!("x: {x}");
  unsafe {
      *ptr1 = *ptr1 * 2;
      *ptr2 = *ptr2 * 2;
      *ptr2 = *ptr1 * 2; 
  }
  println!("x * 8 = {x}");
}