What is wrong with the following code? and what will be the rectified version of this code ?

Question

#include <stdio.h>

#include <stdlib.h>

int *get_val(int y) {

int x = 200; x += y;

return &x; }

int main()

{ int *p, y = 10;

p = get_val(y);

printf("%d\n", *p);

exit(0); }

Answer 1

Hello!

As detailed above in the video, the issue with this code is that x, inside of get_val(), will only exist for as long as the function is running. When you return the reference to x (&x), you're returning memory that has been deleted after the function exits.

The fix to this is making x's memory dynamic. We do this by first saying that x is no longer an int, but an int pointer

int* x = malloc(sizeof(int)); // give me 4 (usually) bytes of memory

Then, we give x a default value of 200

*x = 200; // Notice the derefence operator here

Next, we add the value of y to x

*x += y; // Again, notice the dereference operator (*)

Finally, we fix the return statement by simply returning x, as x's value (without dereferencing) is the, in fact, the memory that holds the answer to our calculation (200 + 10 = 210).

return x; // Not return &x;

Please feel free to reach out with any more questions :)

Michael