/* UA1ZBE Custom Firmware - _sbrk stub
 *
 * Newlib requires _sbrk for malloc/sbrk system calls.
 * Since this firmware uses zero dynamic allocation,
 * we provide a minimal stub that always fails.
 */

#include <sys/types.h>

caddr_t _sbrk(int incr)
{
    /* No heap available — return NULL to indicate failure */
    (void)incr;
    return (caddr_t)0;
}