Quickly jump to event?

Robert O'Callahan robert at ocallahan.org
Wed May 24 12:34:59 UTC 2017


On Wed, May 24, 2017 at 6:48 PM, Benjamin King <benjaminking at web.de> wrote:

> Ok. I was hoping that I could achieve something like that without creating
> the checkpoint in the first place. Maybe this is a weird request. My mental
> model of how rr works is still mostly "hardcore engineering + lots and lots
> of pixie dust" so I have no intuition on what is easy or impossible to do.
> And I have already watched most of your talks about it :-)
>

restart is fast because restoring a checkpoint is fast. Going to an event
where you don't have a checkpoint necessarily takes time proportional to
the distance to the previous checkpoint (or start of trace).

I'll add just a few checkpoints then and navigate between them with restart.
> Your suggestion to keep track of them with eyeballing the event number from
> 'info checkpoints' will be helpful, thanks!
>
> One feature that really should be added to rr itself is the ability to run
>> forward or backward to a specific event without restarting.
>>
> Yes, or to set breakpoints at events. Maybe a hamfisted approach by
> setting a
> conditional breakpoints at the event location + checking the event number
> would already work?
>

The problem there is that you can't easily use the current event number in
an expression. Maybe we should expose the current event number as an extra
pseudo-register to enable that.

Supporting actual breakpoints on events is a bit tricky because we'd have
to provide a stop reason; whatever we do there might confuse gdb. Also we'd
need to find a way to easily let you continue past the breakpoint.

Rob
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