调用 calloc - 内存泄漏 valgrind

Question

以下代码是来自 NCURSES 的示例菜单库。我不确定代码有什么问题，但 valgrind 报告了一些问题。任何想法...

==4803== 1,049 (72 direct, 977 indirect) bytes in 1 blocks are definitely lost in loss record 25 of 36
==4803==    at 0x4C24477: calloc (vg_replace_malloc.c:418)
==4803==    by 0x400E93: main (in /home/gerardoj/a.out)
==4803== 
==4803== LEAK SUMMARY:
==4803==    definitely lost: 72 bytes in 1 blocks
==4803==    indirectly lost: 977 bytes in 10 blocks
==4803==      possibly lost: 0 bytes in 0 blocks
==4803==    still reachable: 64,942 bytes in 262 blocks

源代码:

#include <curses.h>
#include <menu.h>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD   4

char *choices[] = {
    "Choice 1",
    "Choice 2",
    "Choice 3",
    "Choice 4",
    "Choice 5",
    "Choice 6",
    "Choice 7",
    "Exit",
}
;

int main()
{
    ITEM **my_items;
    int c;
    MENU *my_menu;
    int n_choices, i;
    ITEM *cur_item;

    /* Initialize curses */
    initscr();
    cbreak();
    noecho();
    keypad(stdscr, TRUE);

    /* Initialize items */
    n_choices = ARRAY_SIZE(choices);
    my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
    for (i = 0; i < n_choices; ++i) {
        my_items[i] = new_item(choices[i], choices[i]);
    }
    my_items[n_choices] = (ITEM *)NULL;

    my_menu = new_menu((ITEM **)my_items);

    /* Make the menu multi valued */
    menu_opts_off(my_menu, O_ONEVALUE);

    mvprintw(LINES - 3, 0, "Use <SPACE> to select or unselect an item.");
    mvprintw(LINES - 2, 0, "<ENTER> to see presently selected items(F1 to Exit)");
    post_menu(my_menu);
    refresh();

    while ((c = getch()) != KEY_F(1)) {
        switch (c) {
        case KEY_DOWN:
            menu_driver(my_menu, REQ_DOWN_ITEM);
            break;
        case KEY_UP:
            menu_driver(my_menu, REQ_UP_ITEM);
            break;
        case ' ':
            menu_driver(my_menu, REQ_TOGGLE_ITEM);
            break;
        case 10:
            {
                char temp[200];
                ITEM **items;

                items = menu_items(my_menu);
                temp[0] = '\0';
                for (i = 0; i < item_count(my_menu); ++i)
                if(item_value(items[i]) == TRUE) {
                    strcat(temp, item_name(items[i]));
                    strcat(temp, " ");
                }
                move(20, 0);
                clrtoeol();
                mvprintw(20, 0, temp);
                refresh();
            }
            break;
        }
    }
    unpost_menu(menu);
    free_item(my_items[0]);
    free_item(my_items[1]);
    free_item(my_items[2]);
    free_item(my_items[3]);
    free_item(my_items[4]);
    free_item(my_items[5]);
    free_item(my_items[6]);
    free_item(my_items[7]);
    free_menu(my_menu);
    endwin();
}

Answer 1

根据NCURSES Programming Howto ，使用菜单库需要以下步骤:

Initialize curses

Create items using new_item(). You can specify a name and description for the items.

Create the menu with new_menu() by specifying the items to be attached with.

Post the menu with menu_post() and refresh the screen.

Process the user requests with a loop and do necessary updates to menu with menu_driver.

Unpost the menu with menu_unpost()

Free the memory allocated to menu by free_menu()

Free the memory allocated to the items with free_item()

End curses

从您的代码中我可以看出:

• 您不要取消发布菜单(这可能会导致泄漏，或者可能会导致屏幕出现乱码)。
• 释放项目后释放菜单(我猜这可能是也可能不是问题，具体取决于 ncurses 的实现方式)。
• 只有项目的 8 元素数组中的项目 0 和 1 被释放。这可能是泄漏。
• my_items 指针数组永远不会被释放。这肯定是泄漏。

正如@lh3所说，使用-g选项编译会让Valgrind给出丢失内存的行号。

编辑(回应您的评论):my_items 是一个动态分配的指针数组，指向动态创建的菜单项。换句话说，你有一个动态内存块，它包含一堆指向一堆动态分配的 ncurses 结构(菜单项)的指针。因此，要在完成后进行清理，您需要释放每个动态分配的 ncurses 结构，然后您需要释放保存指向这些结构的指针的内存块。

换句话说，每个calloc 或malloc 都需要一个free，每个new_item 都需要一个 free_item，等等。

for (i = 0; i < n_choices; ++i) {
    free_item(my_items[i]);
}
free(my_items);