Question

I am using uthash (http://uthash.sourceforge.net/userguide.html) to use a Hash Table implementation in my C Program.

I am trying to printf the data that is being added to the hash table before and after the addition and I get garbage values when I print it after the malloc. Please see the following code.

void add_user(int user_id, char *name)
{
    printf("User ID : %d Name : %s, user_id,name); // Prints fine !!
    struct my_struct *s;
    s = malloc(sizeof(struct my_struct));
    s->id = user_id;
    strcpy(s->name, name);

    printf("User ID : %d Name : %s, s->user_id,s->name); // Prints User ID fine, but for Name, only half of it is printed right, rest is Garbage !!

    HASH_ADD_INT( users, id, s );
}

If I do the following :

void add_user(int user_id, char *name)
{
    printf("User ID : %d Name : %s, user_id,name); // Prints fine !!

    struct my_struct *s;
    s = malloc(sizeof(struct my_struct));

    printf("User ID : %d Name : %s, user_id,name); // Printing same as previous printf then I get Garbage values printed for Name

}

BUT if I comment out malloc as well, then both printf statements print correctly.

HELP !!!

Answer 1

Gosh, I posted the question and in the next 2 mins I figured it out.

YePHlcK, you are kinda right. However, the thing which didn’t have the memory allocated here was *name which was coming in.

The function was called like this :

add_user(r.user_id, r.name); // r itself is a struct where name was a pointer and not a char array.

Changing name to a char array and then initializing it by using strcpy(r.name,”blah”); and then calling add solved the problem. Because strcpy would take care of allocation of memory ?!?!! Correct me if I am wrong.

Thanks!