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Re: Help please! To track down GC trying to free an already freed object
From: |
Alan Mackenzie |
Subject: |
Re: Help please! To track down GC trying to free an already freed object. |
Date: |
Tue, 2 Apr 2019 20:42:37 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Eli.
On Tue, Apr 02, 2019 at 18:04:22 +0300, Eli Zaretskii wrote:
> > Date: Tue, 2 Apr 2019 11:25:37 +0000
> > From: Alan Mackenzie <address@hidden>
> > With GDB, I can break at the creation of this symbol-with-position
> > object and again at its (first) freeing with this breakpoint:
> > break setup_on_free_list if (v == 0x5555561d0450)
> > . However, this isn't helping me to track down the Lisp object which
> > still references this symbol-with-position. I've tried to find the
> > address of Emacs's data segment, so as to be able to search through it
> > for 0x5555561d0455 in GDB, but this doesn't feel like a very useful
> > thing to do.
> > Could somebody who has experience in this sort of thing please suggest
> > how I might proceed with the debugging, or possibly offer me some other
> > sort of help or hints.
> The usual method of debugging such problems is described in etc/DEBUG,
Apologies, I didn't see this. I read quite a bit of etc/DEBUG, but for
some reason completely missed the bit about GC problems.
> it basically uses the last_marked[] array. You start with the object
> at last_marked[last_marked_index - 1], and go backwards (in circular
> manner), comparing the objects you find in the array with those you
> see in the call-stack frames that call mark_* functions. Just be very
> careful when you print the objects; e.g., never use 'pp', because the
> function it calls cannot handle marked objects.
I'm having some difficult seeing the entire last_marked array with GDB.
I will try to find a solution in the GDB manual.
> If you already tried this, please ask more specific questions.
No, I hadn't. I didn't know about last_marked. I'll see if I can get
further with its help. Thanks!
--
Alan Mackenzie (Nuremberg, Germany).
- Help please! To track down GC trying to free an already freed object., Alan Mackenzie, 2019/04/02
- Re: Help please! To track down GC trying to free an already freed object., Daniel Colascione, 2019/04/02
- Re: Help please! To track down GC trying to free an already freed object., Eli Zaretskii, 2019/04/02
- Re: Help please! To track down GC trying to free an already freed object., Alan Mackenzie, 2019/04/02
- Re: Help please! To track down GC trying to free an already freed object., Daniel Colascione, 2019/04/02
- Re: Help please! To track down GC trying to free an already freed object., Eli Zaretskii, 2019/04/03
- Re: Help please! To track down GC trying to free an already freed object., Alan Mackenzie, 2019/04/03
- Re: Help please! To track down GC trying to free an already freed object., Eli Zaretskii, 2019/04/03
- Re: Help please! To track down GC trying to free an already freed object., Paul Eggert, 2019/04/03