Eyes Above The Waves

Robert O'Callahan. Christian. Repatriate Kiwi. Hacker.

Tuesday 23 February 2016

"These Bugs Are Impossible To Fix Without rr"

Jan de Mooij and the Mozilla JS team just used rr to figure out a GC-related top-crash in Firefox Nightly. The IRC discussion starts here.

I think rr is great for most kinds of bugs, not just the really hard ones. But obviously hard bugs are where there's the most win to be had.


Simon Lindholm
A more permanent link to the IRC discussion: http://logs.glob.uno/?c=mozilla%23jsapi&s=23+Feb+2016&e=23+Feb+2016#c701602
Me: What is rr? I haven’t heard of it before. (Note: I came to this blog from a link to Rewrite Everything In Rust just a few minutes ago) *googles* Me: That EXISTS? Why have I not heard about this before? Why have I not been using this for years? This changes everything. Thank you for creating such an amazing-looking tool.
Steve Fink
@Daniel because it hasn't existed for years, of course! (though I think Microsoft has something similar maybe sorta?) By the way, does rr work with Rust? I mean, I know it should accurately record and replay execution since I assume Rust doesn't make completely oddball syscalls or anything. I guess what I'm really asking is if *gdb* works with Rust.
Yes it does. mbrubeck is apparently using rr to track down Servo intermittents.