wcscpy broken

[Ulrich Weigand]

Hello,

the implementation of wcscpy in glibc appears to be broken:

wchar_t *
wcscpy (dest, src)
     wchar_t *dest;
     const wchar_t *src;
{
  wchar_t *wcp = (wchar_t *) src;
  wint_t c;
  const ptrdiff_t off = dest - src - 1;

  do
    {
      c = *wcp++;
      wcp[off] = c;
    }
  while (c != L'\0');

  return dest;
}

Note the pointer difference 'dest - src'; this invokes undefined
behaviour according to the C standard because dest and src are
not guaranteed to point into the same array.

And in fact this generates incorrect code if one of dest and src
is not sizeof(wchar_t)-aligned  (which, while unusual and a bit
inefficient, is valid as far as I can see).

I've had an actual bug report due to this because gcc 2.95.3 does
not always align wide character string constants to 4 bytes, so a
'wcscpy (str, L"some constant")' can trigger the bug.


Mit freundlichen Gruessen / Best Regards

Ulrich Weigand

--
  Dr. Ulrich Weigand
  Linux for S/390 Design & Development
  IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen
  Phone: +49-7031/16-3727   ---   Email: Ulrich.Weigand@de.ibm.com