私有变量分配正确

背景：我不了解C ++，我了解C。

Problem: In a file called lruTable.hh, I have defined

struct lnode {
    struct lnode *next;
    struct lnode *prev;
};

struct Table {
    struct lnode *list;
    int size;
};

class lruTable {

private:
    struct Table *table;
public:
    lruTable();

};

I want the class constructor lruTable() to initialize the private variable table such that table->list is the head of a doubly linked list, and should be initialized to point to itself in both directions. In a file called lruTable.cc, I have the constructor as

lruTable::lruTable() {
    table = TableAlloc();
}

和表分配器为

struct Table *TableAlloc(void) {
    struct Table *t = (struct Table *) malloc(sizeof(struct Table));
    if (t == NULL) {
        fprintf(stderr, "[ERROR] %s:%d: malloc failed\n", __FILE__, __LINE__);
        exit(EXIT_FAILURE);
    }

    t->size = 0;
    t->list = lnconst(); // A
    return t;
}

最后，lnode分配器为

struct lnode *lnconst(void) {

        struct lnode *ln = (struct lnode *) malloc(sizeof(struct lnode *));
        if (ln == NULL) {
            fprintf(stderr, "[ERROR] %s:%d: malloc failed\n", __FILE__, __LINE__);
            exit(EXIT_FAILURE);
        }

        ln->next = ln;
        ln->prev = ln;
        return ln;
}

I have verified that lnconst() initializes list heads like I want it to. In fact, running the GDB, at line A, the Table t is exactly as I want it to be with t->list->next == t->list and t->list->prev == t->list. However, once TableAlloc() returns in the constructor, something goes wrong and what I have instead is that table->list->next == table->list (desired) and table->list->prev == table (incorrect). I have verified this by printing addresses in GDB.