How to print a stack trace into the stderr from elisp?

Question

There are cases Emacs wont print stack traces on error

How can I make elisp print a stack trace from my own code? (into the stdout/stderr for example)

Something like Python's traceback:

import traceback
traceback.print_exc()

Answer 1

I'm not sure just what you're asking, but does using function backtrace in your code, at the place where you want to see a backtrace, help? C-h f says:

backtrace is a compiled Lisp function in subr.el.

(backtrace)

Print a trace of Lisp function calls currently active.

Output stream used is value of standard-output.

Answer 2

(let ((debug-on-error t))
  (error "test"))

With emacs -Q --batch -l tmp/test.el the following is printed to stderr:

Debugger entered--Lisp error: (error "test")
  signal(error ("test"))
  error("test")
  (let ((debug-on-error t)) (error "test"))
  eval-buffer(#<buffer  *load*> nil "/home/wasa/tmp/test.el" nil t)  ; Reading at buffer position 44
  load-with-code-conversion("/home/wasa/tmp/test.el" "/home/wasa/tmp/test.el" nil t)
  load("/home/wasa/tmp/test.el" nil t)
  command-line-1(("-l" "tmp/test.el"))
  command-line()
  normal-top-level()

If there's a situation where it doesn't work, chances are errors are inhibited by the code in question.