Question

我遇到一个指针，当它传递给一个函数时会改变值...我在各处散布了各种打印语句，确认指针的值没有改变，只是在hashmap中的node-＆gt; prev，这导致我丢失列表并使程序崩溃，因为我希望它有效或为0. Print语句指示指针值在传递给pushmap时发生变化。

我很好奇这是如何可能的：

全部开始：封闭：

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和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;
}

hashmap和hashnode创建函数以防万一：

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;
}

编辑：这就是问题所在：原来这个：

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

应该是：

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

Answer 1

原来这个：

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

应该是：

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

C：推送功能损坏指针？

1 个答案: