Re: san_ignore_object not found at link time

[Philipp Stephani]

Am Sa., 1. Aug. 2020 um 20:32 Uhr schrieb Eli Zaretskii <eliz@gnu.org>:
>
> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Sat, 1 Aug 2020 20:29:29 +0200
> > Cc: Alan Third <alan@idiocy.org>, raman <raman@google.com>,
> >       Emacs developers <emacs-devel@gnu.org>
> >
> > >   alloc.c: In function 'mark_maybe_object':
> > >   alloc.c:4641:14: warning: cast to pointer from integer of different 
> > > size [-Wint-to-pointer-cast]
> > >    4641 |   void *po = (char *) ((intptr_t) (char *) XLP (obj)
> > >         |              ^
> > >
> > > This is a 32-bit build --with-wide-int, in case it matters, where
> > > EMACS_INT is a 64-bit data type.
> >
> > This is due to the unrelated commit a2323c7ccb. (I just happened to
> > push both commits at the same time.)
> > It looks like LISP_WORD_TAG in a wide int build is a 64-bit number, so
> > that the entire expression gets widened to a 64-bit number. However,
> > since it's cast back to a pointer, the value has to fit in 32 bits.
>
> The pointer is there, you just cannot safely extract it by casting to
> a narrower data type.  You need to explicitly mask the MSBs by
> shifting or some other bit fiddling.

IIUC casting between unsigned integer types is guaranteed to have the
same effect.