[Lldb-commits] [lldb] [lldb] Fix assert frame recognizer for Ubuntu 22.04 (PR #109594)

[Pavel Labath via lldb-commits]

labath wrote:

> Is the following correct: Even if the user does not have debug symbols installed, it would always be sufficient to match the **first** named frame.

That *might* work. The complication is that the name of the "first named frame" will different depending on whether you have debug symbols, how your libc was compiled, and its version, which sounds a bit whack-a-mole-ish, but hopefully the list does not end up too long.

> 
> If so, we could change `StackFrameList::SelectMostRelevantFrame` to match against the first frame which has a name available. Although, that might already cause a lot of unwinding, in case no debug info is available at all...

Yes, that sounds like it could be a problem (maybe, I really don't know). I think it might be nicer if we were able to put this unwinding into the hands of the individual recognizer -- so that it could do some checks (and bail out early) on the intermediate frames as well. For example, even though we don't know the names of these "unnamed" frames, we can be sure that all of them are coming from the c library, so we can bail out as soon as we encounter a non-libc frame (*)

(*) I'm ignoring the fact that on linux, none of the libc frames actually have to be in a library called `libc.so.6`. If you're linking your binary statically, the name of the module can be completely arbitrary.

https://github.com/llvm/llvm-project/pull/109594