On Fri, 2016-04-01 at 11:38 +0000, marko(a)kevac.org wrote:
I would like to user libunwind and libdw to get backtrace and symbol
for backtrace from inside SIGSEGV signal handler.
I understand that libdw does not have documentation at all, so I am looking
for help here.
It does have documentation, but it is indeed not as full as we would
like. Please take a look at libdw.h and libdwfl.h
Is it good decision to use libunwind and libdw for getting backtrace
inside signal handler?
Is libdw async signal safe?
You don't need libunwind for unwinding, you can use the
dwfl_frame_thread calls part of libdw described in libdwfl.h for that.
libdwfl is not designed to be signal safe and it wasn't originally
designed as an in-process unwinder. But people have used it for that.
You might want to take a look at the work of Ben Gamari done a couple of
months back on this mailinglist in a thread with the subject "Using dwfl
to enumerate frames of current thread".
If you really need an in-process unwinder then I would recommend you
take a look at the libbacktrace from the GCC project:
If you just want to get a good backtrace when you get a SIGSEGV or other
fatal signal it makes sense to just call eu-stack -P TID on yourself.
fork and exec are signal safe. And then you don't have to try to deal
with a possibly corrupt program.