Re: Building the igc branch on MS-Windows

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Cc: emacs-devel@gnu.org
>> Date: Wed, 24 Apr 2024 21:44:54 +0200
>> 
>> Or IOW, I would propose to see what's special about the pointer in #12.
>
> "Special" in what way?  

Good question. I must admit that I don't know what MPS_FIX1 "let's
through" that MPS_FIX2 doesn't like.

One could for example see in which general direction the pointer points
(is in DATA, is it pdumper_object_p, is_mps, ...). Or maybe control
stack? Or alignment?

Can you read something out the MPS code? Maybe there is a comment
somewhere shedding some light on what it doesn't like?

> Since I can reproduce this at will, I can tell you anything you want
> to know about that, just ask. What do you want to know about it?
>
> The relevant portion of the backtrace is:
>
>   #8  0x007eed88 in amcSegFix (seg=0x9a57490, ss=0x656f814, refIO=0x656f6cc)
>       at poolamc.c:1604
>   #9  0x007d5d16 in SegFix (seg=0x9a57490, ss=0x656f814, refIO=0x656f6cc)
>       at seg.c:793
>   #10 0x007e435b in _mps_fix2 (mps_ss=0x656f818, mps_ref_io=0x656f700)
>       at trace.c:1433
>   #11 0x006ef08a in fix_lisp_obj (ss=0x656f818, pobj=0xcd1aec <globals+396>)
>       at igc.c:428
>   #12 0x006ef27b in scan_staticvec (ss=0x656f818, start=0xccf940 <staticvec>,
>       end=0xcd1940 <consing_until_gc>, closure=0x0) at igc.c:534
>   #13 0x007e4a21 in TraceScanArea (ss=ss@entry=0x656f814,
>       base=0xccf940 <staticvec>, limit=0xcd1940 <consing_until_gc>,
>       scan_area=0x6ef20b <scan_staticvec>, closure=0x0) at trace.c:1566

Hm, don't know. Does staticidx look good? Is the reference tagged? If
so, what type is it? Can you determine if the Lisp obj looks ok?
There is also the igc_header in front of the object which one could look
at.

BTW, how large is that header in your case?

Are you using the default settings when building MPS? If not, maybe it
would be a good idea to start from there.