Summary of Portland meeting

Kyle Huey me at
Sun Dec 7 20:26:51 PST 2014

On Sun, Dec 7, 2014 at 8:17 PM, Yichun Zhang (agentzh)
<agentzh at> wrote:
> Hello!
> On Sun, Dec 7, 2014 at 4:44 PM, Robert O'Callahan wrote:
>> -- Prior to the meeting I brainstormed with Jason Orendorff about how to
>> provide the JS debugger API in an rr replay.
> Hmm, gdb already provides Python as its (only) officially supported
> extension language. Should we consider that first? We've already
> accumulated a lot of advanced debugging tools based on gdb python in
> the nginx-gdb-toolkit project, for example:
> (And all of them seem to be already working fine already in the rr
> replay with gdb.)
> Personally I'm more interested in embedding smaller and faster
> scripting language into such debugging tools, like the standard Lua
> interpreter and LuaJIT 2. When working with large working set, the
> speed is also very important. We've had a hard time with our existing
> gdb python scripts, for example. LuaJIT is usually much faster (and
> much smaller) than V8, unless GC is the bottleneck. But yeah, I
> completely understand there are way more JS programmers than Lua
> programmers out there. Maybe providing more options is a good choice
> here :)
> Well, just my 2 cents :)
> At last but not least, I'm very excited about all the new progress in
> rr and looking forward to making use of it to tackle some really hard
> problems in our own CDN systems.
> Thanks!
> -agentzh
> _______________________________________________
> rr-dev mailing list
> rr-dev at

I think you have misunderstood.  The goal is to debug JavaScript
running inside a recorded Firefox.  Firefox already has an API for
debugging JavaScript, but that requires executing code inside the
replay, which is what roc spoke with jorendorff about.  We're
certainly not trying to add another scripting language to gdb!

- Kyle

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