Well, I'm Back Robert O'Callahan. Christian. Repatriate Kiwi. Mozilla hacker. corrects IE6 width calculation google_ad_section_start(name=default) Thursday, 5 March 2015 Over the last month or so I've added reverse-execution support to rr 's gdb interface. This enables gdb commands such as reverse-continue , reverse-next , reverse-finish and reverse-step . These work with breakpoints and watchpoints, so you can do things like Breakpoint 1, nsCanvasFrame::BuildDisplayList (this=0x2aaadd7dbeb0, aBuilder=0x7fffffffaaa0, aDirtyRect=..., aLists=...) at /home/roc/mozilla-inbound/layout/generic/nsCanvasFrame.cpp:460 460 if (GetPrevInFlow()) { (gdb) watch -l mRect.width Hardware watchpoint 2: -location mRect.width (gdb) reve...