Re: "previous frame inner to this frame" error when unwinding fibers

[Tom Tromey <tom@tromey.com>]

>>>>> "Andrey" == Andrey Turkin via Gdb <gdb@sourceware.org> writes:

Andrey> I'm trying to write a custom unwinder in Python to unwind through
Andrey> boost coroutine (so, follow coroutine stack with its caller's stack).
Andrey> It generally works pretty well except for occasional errors about the
Andrey> inner frame. Obviously, coroutine switches stack so comparing frame
Andrey> pointers makes no sense; so, when caller stack happens to be allocated
Andrey> above coroutine's, the bogus error occurs.
Andrey> I can see in gdb sources that it knows about gcc's split-stacks and
Andrey> apparently arch-specific frames, however I found no way for the
Andrey> unwinder to do anything about it. Is there any way to fix this error
Andrey> with the current gdb, or do I need to patch the sources?

You'll need to patch gdb.  The current code for handling this sort of
thing is totally ad hoc and can't be tweaked by the user or from Python.

Letting Python unwinders affect this seems like a nice feature.  Like
maybe a method on gdb.UnwindInfo that sets a flag, then pipe this
through to the check in get_prev_frame_always_1.

Maybe some other way is better, I don't know.  I'm definitely open to
ideas and I think this is worth solving -- I feel it's been asked for
before.

Tom