Re: MPS: unable to build due to assertion violation in igc_dump_check_object_starts

[Eli Zaretskii <eliz@gnu.org>]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: pipcet@protonmail.com,  eller.helmut@gmail.com,  emacs-devel@gnu.org
> Date: Tue, 23 Jul 2024 20:42:56 +0200
> 
> We are inside of the dump_igc_finish_obj. I see nothing immediately
> suspicious there, hm. 
> 
> Can you try to look at that header? It is at offset ctx->igc_base_offset
> from ctx->buf. Something like
> 
>   p header_type ((char *) ctx->buf + ctx->igc_base_offset)
> 
> Is it already broken? Depending on where exactly you emacs_abort it
> either should still be zeroed or contain something valid like type
> IGC_OBJ_STRING_DATA.

I added emacs_abort here:

  if (ctx->flags.dump_object_contents)
    {
      char *base = (char *) ctx->buf + ctx->igc_base_offset;
      char *end = (char *) ctx->buf + ctx->offset;
      if (ctx->igc_base_offset == 0x6e6c08)
	emacs_abort ();  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
      eassert (end > base);
      char *should_end = igc_dump_finish_obj (ctx->igc_obj_dumped, ctx->igc_type, base, end);
      eassert (should_end >= end);
      dump_write_zero (ctx, should_end - end);
      if (ctx->flags.record_object_starts)
	dump_push (&ctx->igc_object_starts,
		   list2 (dump_off_to_lisp (ctx->igc_base_offset),
			  dump_off_to_lisp (ctx->offset)));
    }

And:

  (gdb) p header_type ((char *) ctx->buf + ctx->igc_base_offset)
  $10 = IGC_OBJ_STRING_DATA

This is _before_ igc_dump_finish_obj was called.