What is CrtIsValidHeapPointer(pUserData)

[ahmed mahmoud]

I am new to C programming language
i am trying to implement linked list using C
but i found that error CrtIsValidHeapPointer(pUserData)
i don't know what is it

my code

struct node
{
    int value;
    struct node * next;
};
 
void addNode(struct node * t)
{
    t->next = (struct node *)malloc(sizeof(struct node));
    if(t->next != NULL)
    {
        (t->next)->value = 5;
        (t->next)->next = NULL;
    }
    else
    {
       printf("FATAL ERROR NO MEMORY");
    }
}
 
 
int main(array<System::String ^> ^args)
{
    struct node * p;
    struct node head;
    head.value = 1;
    head.next = NULL;
    p = & head;
       addNode(p);
    while(p != NULL)
    {
        printf("%d\n",(*p).value);
        p = (*p).next;
    }
    p = &head;
    free(p->next);
    p->next = NULL;
    free(p);
    p = NULL;
    return 0;
}
 

i know that there is lot of things that is not implemented efficiently but now i am focusing only on this error
thanks in advance

[Banfa]

You call free(p) but p has been set to &head and not malloced so you are trying to free memory that is not allocated on the heap and hence you get the error.