Two questions

Robert O'Callahan robert at ocallahan.org
Wed Feb 22 20:01:26 UTC 2017


On Thu, Feb 23, 2017 at 5:54 AM, Juraj <juraj.orsulic at fer.hr> wrote:
> Hello everyone, you are doing wonderful work with rr. I have
> successfully used it in CLion, via its remote gdb debugging feature.
> Another nice thing is that the CLion plug-in, which the folks from
> UndoDB made, that provides "backwards continue", "backwards step",
> etc. buttons in the debug GUI, also works with rr. Rr is also quite a
> lot faster for me than UndoDB.

That's interesting. Thanks!

> I have two questions. First, I am probably not missing something and
> the answer is "impossible", but is it possible to immediately jump to
> a saved state of the application without having to replay all the way
> from the beginning? I am trying to debug an error in an application
> which happens 20 minutes from start, somewhere around the 600 000th rr
> event. It would be nice if I could somehow save the application state
> from there and on the next run immediately start from there.
> Currently, every time I want to debug this trace, I have to wait for
> 20 minutes until the replay reaches this place.

That could be implemented, but it would be quite a lot of work and
it's not a priority for me at this time, nor do I know of any other rr
contributors who are currently interested in it. If someone wanted to
take it on, I'd be happy to provide some guidance.

Is there a reason why you need to restart the debugging session from
scratch multiple times?

> Second, to connect from the gdb inside CLion, I am using the --dbgport
> option. Rr displays the gdb command to execute for connecting, which
> is helpful, but I am missing the rr macros this way. E.g. I cannot use
> "when". Could you also expose a script file which could be sourced
> from gdb in this case?

`rr gdbinit` outputs the script file and might be what you need here.

Rob
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