need help in free() of linked list

hey, i'm have a "heap corruption" error while trying to free linked list.
my structs are:

Code:

---

typedef struct client
{
        char* License;
        struct client* next;
}client;

typedef struct station
{
        char* sName;
        client* clients;
        struct station* next;
}station;

---

linked list of station, each with linked list of clients. stations and clients have a name type char* allocated by malloc.

i'm trying to free the list like this:

Code:

---

void FreeAll(station *st)
{
        client *cl;
        station* temp;
        while (st != NULL)
        {
                cl = st->clients;
                FreeClients(cl);
                temp = st;
                st = st->next;
                free(temp->sName);
                free(temp);
        }
}

void FreeClients(client* cl)
{
        client* temp;

        while (cl != NULL)
        {
                temp = cl;
                cl = cl->next;
                free(temp->License);
                free(temp);
        }
}

---

when i get to free(temp->License); in FreeClients the program crashs down, using debugging i get "heap corruption" error...

thenks for your time...

Since it's a char pointer, my guess is you forgot to count the \0 when allocating space for a string.

To copy "hello", you need 6 chars, not 5.
That is
p = malloc( strlen(s) + 1 );
strcpy( p, s );

Not sure how would that effect freeing a pointer? I suppose free, free the allocated memoryt back to the pool. My guess would be that he's freeing NULL pointer.

ssharish

Freeing NULL pointer is absolutely fine. FYI...

Perhaps I should have said, pointer which hasn't initialised.

Code:

---

char *p;
free(p);  <- crash

---

Though it is very unlikely.

ssharish

well, i can say for sure that i'm note trying to free a NULL pointer, although even if i did that sould be fine...

i did find the root of the problem, it IS as u guys sayed, a problem with free(char*), i did allocated anough space:

Code:

---

client *cl = (client*)malloc(sizeof(client));
cl->License = (char*)malloc(sizeof(str)+1);
strcpy(cl->License, str);

---

even so, when it gets to freeing that freaking char*, the program crushs down...

thenk you all for helping out... the deadline is in 24 hours, and the freeing the allocated memory is the only one standing in my way :\

> cl->License = (char*)malloc(sizeof(str)+1);
Do you know the difference between strlen() and sizeof() ?

There's almost no difference if str is an array.
But if str is a POINTER, then your sizeof is just plain broken.

It does NOT tell you how long the string is!

Oh, and read the FAQ on not casting the result of malloc in a C program.

thenk you salem...

i did sizeof when allocating a struct, forgot to change to strlen when allocating string, that was the problem.

thenx again