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

[Eli Zaretskii <eliz@gnu.org>]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  Paul Eggert <eggert@cs.ucla.edu>,
>   pipcet@protonmail.com,  emacs-devel@gnu.org
> Date: Tue, 16 Jul 2024 16:48:38 +0200
> 
> Helmut Eller <eller.helmut@gmail.com> writes:
> 
> > On Tue, Jul 16 2024, Gerd Möllmann wrote:
> >
> >> 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?
> >
> > That's not a problem because offsetof(struct x, s) = 8. There are 4
> > bytes padding after x.  A problem could be if an unaligned void* is cast
> > to a struct Lisp_Symbol*; let's hope that nobody does that.
> 
> If you're right, and the same holds for the control stack and anything
> else a malloc'd block can contain, then we're safe.
> 
> Since I don't know that for a fact, it's an invalid assumption for me, ATM.

I think it's a fact.