C, free function acts weirdly. why? -

i wrote code generic lists. among functions, has freelist, createlist , copylist. while freeing list created createlist function works fine, when trying free list created copylist function program crashes, checked values when debugging , still see no reason happen. i've got:

void listdestroy(list list) {     if(list==null) return;     listclear(list);     free(list); //<-crashes here when freeing copied lists.     list=null;     return; }  int main() {     list list = listcreate(copystring,freestring);     list copied = listcopy(list);     listdestroy(list);     listdestroy(copied);     printf("success");     return 0; }  list listcreate(copylistelement copyelement, freelistelement freeelement) {     if(!copyelement || !freeelement) return null;     list newlist=malloc(sizeof(*newlist));     if(newlist==null) return null;     newlist->copy = copyelement;     newlist->free= freeelement;     newlist->nodes=null;     newlist->iterator=null;     return newlist; }   node *copynode(node *node, copylistelement copyelement) {     if(node==null) return null;     node *newnode=malloc(sizeof(newnode));     if(newnode==null) return null;     newnode->next=node->next;     newnode->element=copyelement(node->element);     return newnode; }  list listcopy(list list) {     if(!list) return null;     list newlist=malloc(sizeof(newlist));     if(newlist==null) return null;     newlist->copy = list->copy;     newlist->free= list->free;     if(list->nodes!=null)     {         node *firstlink=copynode(list->nodes, newlist->copy);         newlist->nodes=firstlink;         newlist->iterator=firstlink;         node *newpointer=firstlink;         node *listpointer=list->nodes->next;         while(listpointer!=null)         {             node *newlink=copynode(listpointer, newlist->copy);             newpointer->next=newlink;             if(listpointer==list->iterator)             {                 newlist->iterator=newlink;             }             listpointer=listpointer->next;             newpointer=newpointer->next;         }     }     else     {         newlist->iterator=null;         newlist->nodes=null;     }     return newlist; } 

now, while debugging values both list , copied (in main) show same, while freeing list works, free copied causes crash. why?

for starters:

in listcopy() this

list newlist=malloc(sizeof(newlist)); 

should be

list newlist=malloc(sizeof(*newlist)); 

or nicer:

list newlist = malloc(sizeof *newlist); 

---

same in copynode() line:

node *newnode=malloc(sizeof(newnode)); 

which should

node * newnode = malloc(sizeof *newnode); 

---

and btw, in listdestroy() line:

list=null; 

is useless, list copy had been given parameter on call listdestroy().