#include <stddef.h>
extern char _end[];
static char *curbrk = _end;
extern char _heapend; /* End of heap */
void *
sbrk (ptrdiff_t incr)
{
char *oldbrk = curbrk;
if (curbrk + incr > &_heapend)
return (void *) -1;
curbrk += incr;
return oldbrk;
}