C：推送功能的指针损坏了吗？

Question

I'm having trouble with a pointer that changes value as its passed to a function… I have various print statements scattered throughout that confirm that the value of the pointer doesn't change, just node->prev in hashmap, which causes me to lose the list and crash the program because I expect it to be valid or 0. Print statements indicate the pointer value changes when its passed to pushmap .

I'm curious how this is possible:

where it all starts: closure:

RELATION * closure(RELATION * list, RELATION * testdep, DEP_HOLDER * deplist)
{
    RELATION *ret = 0;
    if(list && testdep && deplist)
    {
        HASHMAP * top=buildmap(deplist);
        ret = copyrelation(testdep);
        traversehashmap(ret,top);
     }
     return ret;
}

buildmap:

HASHMAP * buildmap(DEP_HOLDER * deplist)
{
    HASHMAP * ret = 0;
    if(deplist)
    {
        while(deplist)
        {
            DEPENDENCY *dd = deplist->data;
            HASHMAP * nnew = 0;
            nnew = createhashmap(dd->left);
            if(ret)
            {
                pushmap(&ret, nnew);    
            }
            else
            {
                ret = nnew;
            }
            RELATION *holder = dd->right;
            while(holder)
            {
                RELATION * h = getnewrelation(holder->data);
                HASHNODE *node = createhashnode(h);
                if(ret->determines)
                {
                    pushnode(&(ret->determines), node); 
                }
                else
                {
                    ret->determines=node;
                }
                holder=holder->next;
            }
            deplist=deplist->next; 
        }
    }
    return ret;
}

pushmap and pushnode:

void pushmap(HASHMAP **top, HASHMAP **nnew)
{
    (*top)->prev=(*nnew);
    (*nnew)->next=(*top);
    *top=*nnew;
}
void pushnode(HASHNODE **top,HASHNODE *nnew)
{
    nnew->next=(*top);
    *top=nnew;
}

the hashmap and hashnode creation functions just in case:

HASHMAP * createhashmap(RELATION * value)
{
    HASHMAP *ret = (HASHMAP *)malloc(sizeof(HASHMAP *));
    ret->value=value; ret->visited=0; ret->prev=0;
    ret->next=0; ret->determines=0;
    return ret;
}
HASHNODE * createhashnode(RELATION * value)
{
    HASHNODE *ret = (HASHNODE *)malloc(sizeof(HASHNODE *));
    ret->value=value; ret->next=0;
return ret;
}

EDIT: this was the problem: turn out this:

HASHMAP *ret = (HASHMAP *)malloc(sizeof(HASHMAP *));

should be:

HASHMAP *ret = (HASHMAP *)malloc(sizeof(HASHMAP));

Answer 1

turns out this:

HASHMAP *ret = (HASHMAP *)malloc(sizeof(HASHMAP *));

should be:

HASHMAP *ret = (HASHMAP *)malloc(sizeof(HASHMAP));