c - 使用 GLib 包模拟 linux 命令 “who” 的行为 - Valgrind 错误

Question

它获取已登录系统的用户的详细信息并打印其详细信息并将其存储在适当的数据结构中并最终显示。 这是我写的代码。输出是正确的，但我在 valgrind 检查中得到“肯定丢失”和“间接丢失”。 尝试了很多检查泄漏。 谁能帮我清除它们。如果他们告诉我们在编写 prgoram 本身时如何避免这种情况，那将会很有用。 包含所有必要的头文件

void disp(gpointer key, gpointer value, gpointer userdata)
{
printf("%-10s",(char*)key);
g_slist_foreach((GSList*)value, (GFunc)displ, NULL);
printf("\n");
g_free(key);
g_slist_free((GSList*)value);
}

void displ(gpointer value, gpointer userdata)
{
printf("%-25s ", (char *)value);
g_free(value);
}

int main(int argc, char *argv[])
{
if(argc > 1)
{
    printf("Too many input arguments. \n");
    exit(1);
}

GHashTable* hash = NULL;
hash = g_hash_table_new(g_str_hash, g_str_equal);
GSList* list = NULL;

struct utmpx *ret = NULL;
struct passwd *uentry = NULL;
char *id = NULL;
char *name = NULL;
char *hostid = NULL;

while((ret = getutxent())!= NULL)
{
    if(USER_PROCESS == ret->ut_type)
    {       
        /*fetch userid for this user*/
        uentry = getpwnam(ret->ut_user);
        if (NULL == uentry)
        {
            printf("No user found. \n");
            return 0;
        }
        else 
        {   
            /* Create new list for each user */
            list = NULL;
            id = strdup(ret->ut_user);
            name = strdup(uentry->pw_gecos);
            hostid = strdup(ret->ut_host);
            list = g_slist_append(list, name);
            list = g_slist_append(list,hostid);

            g_hash_table_insert(hash, id, list);
                        }
    }
}
/* printing the details of respective users */
g_hash_table_foreach(hash, (GHFunc)disp, NULL);
/*freeing memory created for Hash Table */
g_hash_table_destroy(hash);
return 0;
}

Answer 1

为了释放 Glib 使用的所有内存，您必须使用它的特定函数来执行此操作，因为 Glib 使用引用计数方法来释放对象。我按如下方式更改了您的代码，所有使用的内存均已成功释放。

#include <glib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmpx.h>
#include <pwd.h>
#include <sys/types.h>

void displ(gpointer value, gpointer userdata)
{
    printf("%-25s ", (char *) value);
}

void dell(gpointer value)
{
    g_free(value);
}

void del_list(gpointer value)
{
    g_slist_free_full((GSList*)value, (GDestroyNotify)dell);
}

int disp_del(gpointer key, gpointer value, gpointer userdata)
{
    printf("%-10s",(char*)key);
    g_slist_foreach((GSList*)value, (GFunc)displ, NULL);
    printf("\n");
    return TRUE;
}

int main(int argc, char *argv[]) {
    if (argc > 1) {
        printf("Too many input arguments. \n");
        exit(1);
    }

    GHashTable* hash = NULL;
    hash = g_hash_table_new_full(g_str_hash, g_str_equal, (GDestroyNotify)g_free, (GDestroyNotify)del_list);
    GSList* list = NULL;

    struct utmpx *ret = NULL;
    struct passwd *uentry = NULL;
    char *id = NULL;
    char *name = NULL;
    char *hostid = NULL;

    while ((ret = getutxent())!= NULL) {
        if(USER_PROCESS == ret->ut_type) {
            /* fetch userid for this user */
            uentry = getpwnam(ret->ut_user);
            if (NULL == uentry) {
                printf("No user found. \n");
                return 0;
            } else {
                /* Create new list for each user */
                list = NULL;
                id = strdup(ret->ut_user);
                name = strdup(uentry->pw_gecos);
                hostid = strdup(ret->ut_host);
                list = g_slist_append(list, name);
                list = g_slist_append(list, hostid);
                g_hash_table_insert(hash, id, list);
            }
        }
    }
    /* printing the details of respective users */
    g_hash_table_foreach_remove(hash, (GHRFunc)disp_del, NULL);
    /*freeing memory created for Hash Table */
    g_hash_table_remove_all(hash);
    g_hash_table_destroy(hash);
    return 0;
}