How to find out where a function is called from (backtrace/stacktrace)?

Question

I've hit a problem that region is deactivated (in transient-mark-mode). The function deactivate-mark is called and I would like to find out where (and why) it is called from.

I tried M-x debug-on-entry RET deactivate-mark and it stops but I found no way to find out the caller. Whole displayed stacktrace is:

Debugger entered--entering a function:
* deactivate-mark()

I tried M-x edebug-eval-defun but Edebug does not show the caller either.

How do I find out why (where from) deactivate-mark is called? I'm look for backtrace or stacktrace functinality.

EDIT:

An advice-add trick:

(defun message-show-backtrace ()
  (message "%s" (backtrace-frame 10)))

(advice-add deactivate-mark :before #'message-show-backtrace)

produces nil in *Messages*.

Edit: more info about deactivate-mark: http://emacshorrors.com/posts/deactivate-mark.html

I can reproduce the described behaviour and output. Run emacs -Q, turn on the debug M-x debug-on-entry deactivate-mark, activate mark C-<SPC>, type a character. — Andrew Swann, May 08 '15 at 14:10
You could advise deactiveate-mark and in your advice function use backtrace-frames to get a view of the whole call stack if edebug is not showing what you expect. — Jordon Biondo, May 08 '15 at 16:08
Added edit about advice-add and backtrace-frame. It did not help. — Gracjan Polak, May 09 '15 at 06:29
Regarding the reproduction from @AndrewSwann, it is worth noting that typing a character typically runs self-insert-command and "self-insert-command is an interactive built-in function in 'C source code'." This, together with the other behavior noted so far, suggests that one will have to debug with gdb. — Joe Corneli, May 29 '15 at 22:05
From reading the question, it sounded like mark was being unexpectedly deactivated. Meanwhile the behaviour described by @AndrewSwann is perfectly expected (the region is deactivated when you type something). If the behaviour you get matches Andrew's, please clarify what you want to do. — Malabarba, May 29 '15 at 23:43
Your advice-add contains a syntax error: the deactivate-mark should be 'deactivate-mark. Also, backtrace-frame for me seems to just return nil, Idk why. Instead (backtrace) works more or less, except that it prints to *Messages* instead of returning a string. There's this answer though that describes how to make (backtrace) return a string. — Hi-Angel, Mar 27 '24 at 22:50

score 4 · Accepted Answer · edited Apr 13 '17 at 12:52

From command_loop_1 in keyboard.c.

  ...
  if (!NILP (BVAR (current_buffer, mark_active))
  && !NILP (Vrun_hooks))
{
  /* In Emacs 22, setting transient-mark-mode to `only' was a
     way of turning it on for just one command.  This usage is
     obsolete, but support it anyway.  */
  if (EQ (Vtransient_mark_mode, Qidentity))
    Vtransient_mark_mode = Qnil;
  else if (EQ (Vtransient_mark_mode, Qonly))
    Vtransient_mark_mode = Qidentity;

  if (!NILP (Vdeactivate_mark))
    /* If `select-active-regions' is non-nil, this call to
       `deactivate-mark' also sets the PRIMARY selection.  */
    call0 (Qdeactivate_mark);
  else
  ...

That seems to be the only place where Qdeactivate_mark is called in all of src/*.c. So my guess is that this what you're running into.

Note, I am not an expert on Emacs C. I poked around with gdb --args src/emacs -Q after reading How to compile emacs with debug symbols?.

How to find out where a function is called from (backtrace/stacktrace)?

1 Answers1