Make a memory diagram. Copying lists

$```$

The following code tries to copy a list:

struct llist $*$list$\_$cp$\_$bad$($struct llist $*$ll$)\{$

struct llist $*$newlist $=$

malloc$($sizeof$($struct llist$))$;

newlist$->$front $=$ ll$->$front;

return newlist;

$\}$

Our attempt to use it seems to work:

struct llist $*$ll $=$ list$\_$create$()$;

list$\_$insert$\_$front$($ll$,7)$;

list$\_$insert$\_$front$($ll$,5)$;

list$\_$insert$\_$front$($ll$,3)$;

list$\_$insert$\_$front$($ll$,10)$;

struct llist $*$ll$\_$copy $=$ list$\_$cp$\_$bad$($ll$)$;

list$\_$print$($ll$)$;

list$\_$print$($ll$\_$copy$)$;

$->($cons $10($cons $3($cons $5($cons $7$ empty$))))$

$->($cons $10($cons $3($cons $5($cons $7$ empty$))))$

$```$

Here is the memory diagram for llist $*$ll:

Draw a memory diagram after

list$\_$cp$\_$bad executes.

We see that these lists share nodes. If we mutate nodes in ll $,$ we also mutate nodes in ul$\_$copy; they are the same nodes.

list$\_$cp$\_$bad makes a shallow copy; it copies the values of the fields of tlist $.$ What we need is a deep copy.