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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: |
Thu, 4 Apr 2019 18:57:55 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Eli.
On Wed, Apr 03, 2019 at 07:43:22 +0300, Eli Zaretskii wrote:
> > Date: Tue, 2 Apr 2019 20:42:37 +0000
> > From: Alan Mackenzie <address@hidden>
> > Cc: address@hidden
> > I'm having some difficult seeing the entire last_marked array with GDB.
> > I will try to find a solution in the GDB manual.
> You want "set print elements unlimited", I think.
> However, my recommendation is to examine the array one element at a
> time, moving back to the previous one only when you understand what
> the element you've looked at is and whether it is or isn't related to
> the problem. Also, last_marked array is written cyclically, so you
> may need to wrap around the index to see the objects in the right
> order.
I've found the bug.
In the garbage collection, it's necessary for Qsymbols_with_pos_enabled
to be bound to nil. (That's the variable which enables symbols with
position).
I had bound that variable to nil in Fgarbage_collect, not noticing that
there are calls to the C function garbage_collect which bypass the
primitive. This was the bug.
As a result, the pseudovector (Symbol "nil" at position 339) was caught
by a NILP, causing it not to get marked. So it got swept away, even
though it was still live.
So I've spent several days on this, but as a consolation I now know GDB
much better than I did before. ;-). My branch now builds successfully.
Thanks for all the help!
--
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
Re: Help please! To track down GC trying to free an already freed object., Alan Mackenzie, 2019/04/02