gdb doesn't print Lisp backtrace in some circumstances.

[Alan Mackenzie <acm@muc.de>]

Hello, Emacs.

Yesterday I got a core dump from a segmentation fault in Emacs (my
development version, not master).  I loaded this into gdb inside Emacs
to have a look at it.

The backtrace command output the C data as it should, but on coming to
the Lisp backtrace gave an error message about there needing to be a
process running to "do this".  (I don't have the exact message any
more.)  It would seem these fancy Lisp facilities only work when the
process that produced them is still running.

All the information required to produce this Lisp backtrace is present
in the core dump.  Would it be possible, perhaps, to modify our .gdbinit
to use the running Emacs to process the core dump, or something like
that?  Extracting useful information from the C backtrace is slow and
tedious in the extreme.

-- 
Alan Mackenzie (Nuremberg, Germany).