free()ing a pointer

[Markus]

If we free() a pointer, is the pointer free()d or the memory the pointer points to?

#include <stdlib.h>
#include <stdio.h>
#include "stack.h"
 
void stack_new(stack *st) 
{
    st->log_len = 0;
    st->alloc_len = 4;
    st->elems = malloc(4 * sizeof(int));
}
 
void stack_dispose(stack *st)
{
    free(st->elems);
}
 
stack *stack_newx(void)
{
    stack *st = (stack *)malloc(sizeof(stack));
    stack_new(st);
    return st;
}
 
void stack_disposex(stack *st)
{
    free(st); // Does this free the pointer or memory?
}

Edit: since this pointer points to the memory, I guess it will free the memory. *stupid*.

Mark.

[sumeshnb]

when a pointer is freed the memory it pointing to is freed...after freeing also the pointer points to that particular location in memory.

[Markus]

@sumeshnb
Right. I get that. So, after the memory pointed to is freed, the pointer still points to that memory location?

[drhowarddrfine]

Yes. The pointer still exists and still points to that location.

[Markus]

@drhowarddrfine
Thanks, Doc.

[donbock]

Some of the confusion comes from using the phrase "freeing a pointer". This phrase certainly gives the impression that the pointer itself is being freed. Since that is not the case, I suggest you avoid using that phrase.

The code snippet in the OP "called function free(), passing it the value of a pointer". The result was to free the memory pointed to by the pointer variable.

[drhowarddrfine]

And to add the obvious, the same pointer can be used to point to new allocated memory or anything else of the same type.