We just released rr 1.2 and I think this would be a good time for people to try to use it for one of the tasks it was designed for: debugging intermittent test failures.
Consult http://rr-project.org for more information, but the gist is this: you can use rr to record the execution of Firefox test suites (with 32-bit Linux Firefox builds). If you see a test failure occur while recording with rr, you will be able to replay that execution and use gdb to debug the replay. The replay is exact, so the same failure will reoccur every time you replay, and in exactly the same way, including addresses of objects etc. This means that once you've recorded a test failure, it's just a matter of time before you figure out the bug. The steps to get started doing this are roughly as follows: 1) Install rr on a Westmere-or-later Linux system (or VM with performance counters virtualized), build 32-bit Firefox (opt or debug) and verify that recording Firefox works for you. If it doesn't, please file a github issue or check https://github.com/mozilla/rr/issues/973 if your system is Haswell-based. 2) (Optional) Enable chaos mode by editing mfbt/ChaosMode.h to return true for isActive. 3) (Optional) Enable shuffling of mochitests and reftests (sorry, I have a patch that needs to land for the latter). 4) Create a script somewhere called rr-record that does "exec ~/rr/bin/rr record $*" 5) Run your testsuite using mach, and pass the options --debugger rr-record 6) If necessary, run step 5 in a loop until you see test failures you want to fix, clearing out ~/.rr periodically so your disk doesn't fill. 7) Run "rr replay -a" to verify that the replay works. If it doesn't, report an rr bug. 8) Run "rr replay" to debug with gdb. Consult the rr documentation for more information about that. cjones and I are usually around on #research if you have any issues with rr, and we'd love to hear from you. Rob -- Jtehsauts tshaei dS,o n" Wohfy Mdaon yhoaus eanuttehrotraiitny eovni le atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o Whhei csha iids teoa stiheer :p atroa lsyazye,d 'mYaonu,r "sGients uapr,e tfaokreg iyvoeunr, 'm aotr atnod sgaoy ,h o'mGee.t" uTph eann dt hwea lmka'n? gBoutt uIp waanndt wyeonut thoo mken.o w _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
