Re: Why is it so difficult to get a Lisp backtrace?

[Lars Ingebrigtsen]

Alan Mackenzie <acm@muc.de> writes:

>> This third group of users is poorly catered for by the current collection
>> of mechanisms.  See also bug #56201, with thanks to Andreas and Lars who
>> helped me get to the bottom of it.  To be reasonably sure of getting a
>> backtrace, it seems one needs to do all of the following:
>> (i) (setq debug-on-error t).
>> (ii) (setq debug-on-signal t).
>> (iii) Bind debug-ignored-errors to nil.
>> (iv) Pray.

You probably also need to ensure that inhibit-redisplay is nil at the
point of the error, I think?  (At least I vaguely recall having to
remove some of those bindings to get a backtrace...)

> I mean something like the following, which to a first approximation,
> works.  To use it, do M-x debug-next-command and the execute the command
> expected to give errors:

I like it, but it may not be useful in all contexts -- errors are used
as a programming mechanism here and there (i.e., throwing an error
symbol to be caught by the caller), and you'll get backtraces from these
non-error errors, too, unfortunately.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no