#include <string.h>
#include <stdint.h>
#include <limits.h>

#define ALIGN (sizeof(size_t))
#define ONES ((size_t)-1/UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX/2+1))
#define HASZERO(x) (((x)-ONES) & ~(x) & HIGHS)

char *stpcpy(char *d, const char *s)
{
#if defined(__GNUC__) && __GNUC__ >= 4
        typedef size_t __attribute__((__may_alias__)) word;
        word *wd;
        const word *ws;
        if ((uintptr_t)s % ALIGN == (uintptr_t)d % ALIGN) {
                for (; (uintptr_t)s % ALIGN; s++, d++)
                        if (!(*d=*s)) return d;
                wd=(void *)d; ws=(const void *)s;
                for (; !HASZERO(*ws); *wd++ = *ws++);
                d=(void *)wd; s=(const void *)ws;
        }
#endif
        for (; (*d=*s); s++, d++);

        return d;
}