Re: [libunwind] Unwinding using the context passed to a signal handler (doesn't work)

[David Mosberger]

>>>>> On Wed, 17 Mar 2004 16:18:45 +0100, Johan Walles <address@hidden> said:

  Johan> Note that the function that crashes (crash()) isn't part of
  Johan> the first stack trace (initialized using the context passed
  Johan> to the signal handler).

  Johan> Why isn't it?  And if I want that, what should I do?  Am I
  Johan> using libunwind correctly?

The program attempts to unwind from a sigcontext_t, by casting it to
ucontext_t.  That can't work.  There is a reason these are different
types, even though they have the same layout: unw_getcontext() returns
the _preserved_ state in ucontext_t, whereas a signal handler saves
only the _scratch_ state in sigcontext.  To initiate unwinding, the
preserved state is needed.  You should be able to just do a
unw_getcontext() anywhere in the signal handler and then step until
you hit the signal frame (as indicated by unw_is_signal_frame()).

        --david