Re: Unwind cycle detection false positive mixing frame view and backtrace

[Tom Tromey <tom@tromey.com>]

>>>>> "Carlos" == Carlos Sánchez de La Lama via Gdb <gdb@sourceware.org> writes:

Carlos> I have found a problem which cases a false positive detection of cycles
Carlos> when "frame view" specifier is used in combination with "bt"; the
Carlos> consequence is affected frames are (wrongly) reported as impossible to be
Carlos> further traversed.
...

Carlos> I was going to create a bug report, but I want to hear comments on the
Carlos> expected behaviour here:
Carlos> Option 1) this works as expected, you are not supposed to "frame view" frames
Carlos> which are on your current backtrace
Carlos> Option 2) make "frame view" reset the frame stash before and after running
Carlos> Option 3) condition the frame traverser to skip the cycle detection
Carlos> when using "frame view"

Carlos> Suggestions?

I don't really know the answer, but I didn't want your note to go too
long without some kind of response.

It's not clear to me we ever really worked out all the implications of
"frame view".

On the one hand, it seems like it should flush the frame cache and let
you "bt".  On the other hand, the docs say you can then do "frame level
0" to reset back to gdb's "native" notion of frames -- which seems a
little incoherent to me.

If we had green thread support I guess I'd be tempted to make "frame
view" make a temporary, gdb-side-only green thread.  Then switching away
from the thread would delete the frame view.

Tom