Simple Warning, How do I remove -- Missing Prototype 'free'

Here's a snippet, real basic stuff...

I am worried about commenting it out and not giving back the
memory...  I though as loc was declared local I need to free it local
hence the use of free() but why the "missing prototype free"
error...

If it helps I have a bunch of other missing prototype errors like atol
and malloc.  All standard library stuff not my own protos.

#include <stdio.h>
#include "xmlapi.h"

ME * var_one;
ME * var_two;
char * loc;
FILE * file;

int main (int argc, char *argv[])
{

   ...Do Stuff...
   free (loc);
}

Thanks in advance.

Christopher