c - 自由(): random error in recursive function

Question

我尝试用 C 语言编写 ls 命令，但 -R 选项有问题。

输出:

/Applications/Atom.app/Contents/Resources/app/apm/node_modules/es5-ext/array/of:
implement.js
index.js
is-implemented.js
shim.js
ft_ls(61021,0x7fffc25583c0) malloc: *** error for object 0x7fedfd273700: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
[1]    61021 abort      ./ft_ls -R /

好吧，知道我的递归函数:

static void upper_r_option(t_opt *option, char *dirname)
{
    char    **order;
    char    *path;
    int     i;

    i = 0;
    order = ft_get_order(dirname, option);
    if (option->l)
        ft_getdata(order, dirname);
    else
        ft_puttab(order);
    while (order[i])
    {
        path = upper_r_checker(order[i], dirname);
        if (path != NULL)
        {
            upper_r_option(option, path);
            free(path);
        }
        i++;
    }
    ft_free_tab(order);
    ft_putstr("FREE : OK\n");
    return ;
}

我的错误出现在 ft_free_tab 中递归函数的末尾。我不明白的是为什么我有时能够释放而随机地却不能。当我启动程序“./ft_ls -R/”时，我在错误之前看到一些“FREE:OK”。

我的 ft_free_tab :

void    ft_free_tab(char **tab)
{
    int i;

    i = 0;
    if (tab[1] == NULL)
        free(tab);
    else if (tab != NULL)
    {
        while (tab[i])
        {
            free(tab[i]);
            i++;
        }
        free(tab);
    }
}

编辑:

我试图调试这个，但出了问题。

输出:

This NULL = LICENSE


My order after R =
LICENSE
inherits.js
inherits_browser.js
package.json


Path strdup : 0x7f8218700640
/Applications/Atom.app/Contents/Resources/app/apm/node_modules/inherits
Path in strjoin : 0x7f8218700640
YOPath strjoin1 : 0x7f8218701740
==========================

/Applications/Atom.app/Contents/Resources/app/apm/node_modules/inherits/
Path in strjoin : 0x7f8218701740
ft_ls(17078,0x7fffac1623c0) malloc: *** error for object 0x7f8218700690: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
[1]    17078 abort      ./ft_ls -R /

此错误位于 upper_r_c​​hecker 和 ft_str_fjoin 中。我试图释放旧路径，但我做不到。

upper_r_option 和 upper_r_c​​hecker:

static char *upper_r_checker(char *this, char *dirname)
{
    char    *path;

    path = ft_strdup(dirname);
    printf("Path strdup : %p\n", path);
    if (!ft_issame(path, "/"))
        path = ft_str_fjoin(path, "/", 1);
    printf("Path strjoin1 : %p\n", path);
    ft_putstr("==========================\n\n");
    path = ft_str_fjoin(path, this, 1);
    ft_putstr("==========================\n\n");
    if (ft_type(path) == 'd' && !ft_issame(this, ".") &&
    !ft_issame(this, "..") && ft_error(path, 1))
    {
        ft_putchar('\n');
        ft_putstr(path);
        ft_putstr(":\n");
        ft_putstr("\nThis = ");
        ft_putstr(this);
        ft_putstr("\n\n");
        return (path);
    }
    else
    {
        ft_putstr("\nThis NULL = ");
        ft_putstr(this);
        ft_putstr("\n\n");
        if (path != NULL)
            free(path);
        return (NULL);
    }
}

static void upper_r_option(t_opt *option, char *dirname)
{
    char    **order;
    char    *path;
    int     i;

    i = 0;
    order = ft_get_order(dirname, option);
    if (option->l)
        ft_getdata(order, dirname);
    else
        ft_puttab(order);
    while (order[i])
    {
        path = upper_r_checker(order[i], dirname);
        if (path != NULL)
        {
            upper_r_option(option, path);
            free(path);
        }
        ft_putstr("\nMy order after R = \n");
        ft_puttab(order);
        ft_putstr("\n\n");
        i++;
    }
    ft_free_tab(order);
    return ;
}

ft_str_fjoin:

char    *ft_str_fjoin(char *s1, char *s2, int i)
{
    char    *fraiche;
    int     len;

    if (s1 == NULL || s2 == NULL)
        return (NULL);
    len = (ft_strlen(s1) + ft_strlen(s2) + 1);
    fraiche = ft_memalloc(len);
    if (fraiche == NULL)
        return (NULL);
    ft_strcat(fraiche, s1);
    ft_strcat(fraiche, s2);
    fraiche[len] = '\0';
    if (i == 1)
    {
        ft_putstr(s1);
        ft_putchar('\n');
        printf("Path in strjoin : %p\n", s1);
        free(s1);
        ft_putstr("YO");
    }
    if (i == 2)
        free(s2);
    if (i == 3)
    {
        free(s1);
        free(s2);
    }
    return (fraiche);
}

为什么无法释放 0x7f8218701740 (Cf.Output) ？

Answer 1

您有一个拼写错误:

    if (tab[1] == NULL)    // this is digit '1'

应该是

    if (tab[i] == NULL)     // this is variable 'i'

<小时/> tab 显然是一个以空结尾的字符串指针数组。最后一个元素为 null，表示数组的末尾。当 tab 本身为 null 时，永远不会调用该函数。该函数可以简化并浓缩为:

void ft_free_tab(char **tab)
{
    int i= 0;
    while (tab[i]) free(tab[i++]);
    free(tab);
}