請教這篇Secure, Efficient and Easy C programming的原理

http://irccrew.org/~cras/security/c-guide.html

"Secure, Efficient and Easy C programming" 這篇文章看大意

是在介紹利用記憶體佈局中的 stack 來達成不需手動經由malloc / free

動態配置/回收記憶體的技巧，但想必是我的 C 語言學得太差，看不懂他範例程式

是如何使用到 stack。如果有 C 達人讀過這篇文章，能否為在下解惑，說明一下

作者用了什麼方式來操控 stack 在自己的程式中模擬「動態記憶分配」的功能，

謝謝

// 以下是網頁上的第一個程式，我讀得一頭霧水，看不出「動態分配」在哪？

/* asprintf()-like functon, but allocates the memory from data stack */
const char *t_printf(const char *fmt, ...) __attribute__((format (printf, 1,
2)));

void client_input(struct client *client)
{
    const char *cmd;
    int i;

    cmd = read_command(client);
    if (cmd == NULL)
        return;

    if (strcasecmp(cmd, "status") == 0) {
        time_t now = time(NULL);
        client_send(client, t_printf("Time: %s", ctime(&now)));
        client_send(client, t_printf("Clients: %u", clients_count));

        for (i = 0; i < 10000; i++) {
            /* without an extra stack frame here, we'd allocate the
               t_printf() 10000 times before freeing them all.
               That's probably not be very good. */
            t_push();
            client_send(client, t_printf("%d: %u", i, stuff[i]));
            t_pop();
        }
    } else {
        client_send(client, t_printf("Unknown command: %s", cmd));
    }
}

void main_loop(void)
{
    unsigned int i, id;
    fd_set rfds;

    if (select(max_fd, &rfds, NULL, NUL, NULL) <= 0)
        return;

    for (i = 0; i < clients_count; i++) {
        if (FD_ISSET(clients[i].fd, &rds)) {
            id = t_push();
            client_input(&clients[i]);
            if (t_pop() != id) {
                /* we could simply call the missing t_pop()s,
                   but this  usually indicates a problem which
                   we want to know. for example we might have
                   leaked it inside a for loop which caused
                   unnecessarily large memory usage. */
                panic("missing t_pop()");
            }
        }
    }
}




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☆ [Origin:椰林風情] [From: host-219-70-179-157.dynamic] [Login:  3] [Post:  0]
推 purpose:t_printf 的實作應該是關鍵吧..但作者沒給
推 bob123:t_printf應該只是用__attribute__讓編譯器
→ bob123:檢查printf的參數吧, 看了一下重點應該在
→ bob123:t_push()和t_pop()...
→ bob123:看了一下網站上的data-stack.c 感覺像是用
→ bob123:double linked list實作mem pool來當堆疊用
推 purpose:您說的是，我好像懂了。把 malloc 都改用
→ purpose:t_malloc 在配置空間的同時跟 Heap 管理器
→ purpose:一樣，用鏈結串列把最後於 t_pop 時要一起
→ purpose:free 的 heap blocks 串起來..
推 EdisonX:p 大指的是這篇嗎？ http://ppt.cc/aoSW