Re: Help please! To track down GC trying to free an already freed object.

[Daniel Colascione]

> Hello, Eli.
>
> On Tue, Apr 02, 2019 at 22:21:26 +0300, Eli Zaretskii wrote:
>> > Date: Tue, 2 Apr 2019 12:09:59 -0700
>> > From: "Daniel Colascione" <address@hidden>
>> > Cc: address@hidden
>> >
>> > rr is incredibly helpful for debugging this sort of problem. See
>> > https://rr-project.org/. You can record an rr session containing the
>> > crash, replay it, get to the crash, and then reverse-next,
>> reverse-finish,
>> > and reverse-continue your way through the GC, running it in reverse
>> until
>> > you find whatever it is that made mark_object on the dead object
>> happen.
>
>> GDB supports reverse execution as well, on some platforms.
>
> On my GNU/Linux system, I tried to run 'reverse-next', and got the error
> message:
>
>     Target multi-thread does not support this command.
>
> .  :-(  I suppose I could reconfigure without multi threading, but then
> the bug (which is reproducible) probably wouldn't happen in the same
> place.

I don't think I've ever gotten pure-GDB reverse execution to work
correctly. rr Just Works for me in every instance I've tried it.