[Lldb-commits] [PATCH] D15407: When stepping in/over source lines, combine the addr ranges of all line table entries w/ same line num

Jason Molenda via lldb-commits lldb-commits at lists.llvm.org
Fri Dec 11 15:24:25 PST 2015

jasonmolenda added a comment.

Thanks Jim, I'll fix those issues.

With line 0's, I think there are three scenarios of interest (none of this contradicts what you wrote, I'm just spelling it out for myself):

1 We are stepping over a source line and we find a line 0.  We want to include that line 0.  If that same source line # appears after line 0, continue to extend our stepping range.

2 We are somehow starting on a line 0 (which lldb will try to avoid - but an asynchronous interrupt may have put us here).  I think the debugger will show the first non-zero line number as the "currently executing" source line in this case.  So a 'next' should consume the line 0 that we're on, plus the next source line that we encounter.

3 We're stepping a source line "n", we branch over a different source line and find ourselves in a line 0.  In this case we want to consume the 0, and if we find the next non-zero line number is "n", continue to expand the range.  If it's non-"n", then we need to stop expanding the range.

#2 and #3 are trickily similar; I implemented #2 (if we start with a line 0, adopt the first non-zero line num we encounter) in this patch.  #3 won't actually happen because ThreadPlanStepRange::InRange() (which handles the case where we've finished stepping through a range of addresses and we look at the new pc to see if it is still a part of the same line -- so realistically, when we've branched over another source line now that we extend line ranges) treats "the new pc is the same line number as the original line number" and "the new pc is line number 0" separately - and if the new pc is line 0, it replaces the line number with the original line number.  (this isn't a change by me - that was the existing code behavior)

It's a subtle behavior and that's probably not good to rely on it happening to be written correctly - I almost tried to combine the "line 0" and "non-line 0" sections of ThreadPlanStepRange::InRange when  I was writing the patch and it took me a minute to think through the implications of doing that.



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