free()ing a pointer

Markus

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

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#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

Quote:

Originally Posted by 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.

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

Quote:

Originally Posted by drhowarddrfine

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

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.

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