__stpncpy (q, p, buflen - unklen);
memcpy (q, p, MIN (&numbuf[21] - p, buflen - unklen));
__strerror_r (int errnum, char *buf, size_t buflen){  int system;  int sub;  int code;  const struct error_system *es;  extern void __mach_error_map_compat (int *);  __mach_error_map_compat (&errnum);  system = err_get_system (errnum);  sub = err_get_sub (errnum);  code = err_get_code (errnum);  if (system > err_max_system || ! __mach_error_systems[system].bad_sub)    {      /* Buffer we use to print the number in.  For a maximum size for	 `int' of 8 bytes we never need more than 20 digits.  */      char numbuf[21];      const char *unk = _("Error in unknown error system: ");      const size_t unklen = strlen (unk);      char *p, *q;      numbuf[20] = '\0';      p = _itoa_word (errnum, &numbuf[20], 16, 1);      /* Now construct the result while taking care for the destination	 buffer size.  */      q = __mempcpy (buf, unk, MIN (unklen, buflen));      if (unklen < buflen)	__stpncpy (q, p, buflen - unklen);      /* Terminate the string in any case.  */      if (buflen > 0)	buf[buflen - 1] = '\0';      return buf;    }  es = &__mach_error_systems[system];  if (sub >= es->max_sub)    return (char *) es->bad_sub;  if (code >= es->subsystem[sub].max_code)    {      /* Buffer we use to print the number in.  For a maximum size for	 `int' of 8 bytes we never need more than 20 digits.  */      char numbuf[21];      const char *unk = _("Unknown error ");      const size_t unklen = strlen (unk);      char *p, *q;      size_t len = strlen (es->subsystem[sub].subsys_name);      numbuf[20] = '\0';      p = _itoa_word (errnum, &numbuf[20], 10, 0);      /* Now construct the result while taking care for the destination	 buffer size.  */      q = __mempcpy (buf, unk, MIN (unklen, buflen));      if (unklen < buflen)	{	  q = __mempcpy (q, es->subsystem[sub].subsys_name,			 MIN (len, buflen - unklen));	  if (unklen + len < buflen)	    {	      *q++ = ' ';	      if (unklen + len + 1 < buflen)		__stpncpy (q, p, buflen - unklen - len - 1);	    }	}       /* Terminate the string in any case.  */      if (buflen > 0)	buf[buflen - 1] = '\0';      return buf;    }  return (char *) _(es->subsystem[sub].codes[code]);}