Re: MPS: assertion failed: header_type (h) != IGC_OBJ_FWD

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Paul Eggert <eggert@cs.ucla.edu>,  pipcet@protonmail.com,
>   emacs-devel@gnu.org,  eller.helmut@gmail.com
> Date: Tue, 16 Jul 2024 15:47:26 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> >> Cc: Emacs Devel <emacs-devel@gnu.org>,  Helmut Eller 
> >> <eller.helmut@gmail.com>
> >> Date: Tue, 16 Jul 2024 15:02:24 +0200
> >> 
> >> The handlerlist_sentinel didn't help, BTW, but I had another idea today.
> >> The function scan_ambig assumes that that references are aligned on word
> >> boundaries (8 bytes here). I haven't checked (and I'm too lazy to check
> >> :-)), but that assumption doesn't have to be true.
> >
> > I think it _is_ true.  At least the original allocation code in
> > alloc.c made sure it was true.  Paul, am I right?
> 
> That's probably a misunderstanding. I'm thinking about a block of memory
> containing references, and the alignment of these references, not the
> alignment of the block.
> 
> Example with sizeof(int) = 4, and sizeof(void *) = 8
> 
>   struct x
>   {
>     int x;
>     struct Lisp_Symbol *s;
>   };
> 
> What about the offset of x::s?

The pointer or the Lisp_Symbol struct it points to?