How do I get edebug online?

How do I get edebug online?

[Davin Pearson]

First I eval the following sexp:

(setq edebug-all-defs t)

Then I issue the following command on the following code which resides
in a file called:
~/java-training-wheels/dlisp/coolmacs/dmp-grep--splat-file.el.
The command is \C-\M-x.  The file contains the following defun:

(defun fac (n)
  (when (= 5 n)
    (message "Foo bar")
    (edebug)
    (message "Rita Hayworth"))
  (if (< 0 n)
      (* n (fac (1- n)))
    1))

Execute the following command:

(fac 10)

and it comes back at you with the following backtrace: (see after this
backtrace for my question)

Debugger entered: nil
  apply(debug nil nil)
  edebug()
  (progn (message "Foo bar") (edebug) (message "Rita Hayworth"))
  (if (= 5 n) (progn (message "Foo bar") (edebug) (message "Rita
Hayworth")))
  fac(5)
  (* n (fac (1- n)))
  (if (< 0 n) (* n (fac (1- n))) 1)
  fac(6)
  (* n (fac (1- n)))
  (if (< 0 n) (* n (fac (1- n))) 1)
  fac(7)
  (* n (fac (1- n)))
  (if (< 0 n) (* n (fac (1- n))) 1)
  fac(8)
  (* n (fac (1- n)))
  (if (< 0 n) (* n (fac (1- n))) 1)
  fac(9)
  (* n (fac (1- n)))
  (if (< 0 n) (* n (fac (1- n))) 1)
  fac(10)
  eval((fac 10) nil)
  elisp--eval-last-sexp(nil)
  eval-last-sexp(nil)
  funcall-interactively(eval-last-sexp nil)
  call-interactively(eval-last-sexp nil nil)
  command-execute(eval-last-sexp)

My question is this:

How do I go about typing g (goto next breakpoint)

Do I need to pop the stack and go back to the top level?

Do I enter the command g in the *Backtrace* window?
or in the file window
~/java-training-wheels/dlisp/coolmacs/dmp-grep--splat-file.el

How do I go about printing out "Rita Hayworth" ? I have searched my
*Messages* buffer but I have not found Rita Hayworth anywhere.  Judging
from the Elisp manual it seems that I need to type in the "g" command but I
am perplexed at where I need to issue this command!

Re: How do I get edebug online?

[Eric Abrahamsen]

Davin Pearson <davin.pearson@gmail.com> writes:

> First I eval the following sexp:
>
> (setq edebug-all-defs t)
>
> Then I issue the following command on the following code which resides
> in a file called:
> ~/java-training-wheels/dlisp/coolmacs/dmp-grep--splat-file.el.
> The command is \C-\M-x.  The file contains the following defun:
>
> (defun fac (n)
>   (when (= 5 n)
>     (message "Foo bar")
>     (edebug)
>     (message "Rita Hayworth"))
>   (if (< 0 n)
>       (* n (fac (1- n)))
>     1))

You don't insert an actual call to (edebug) in your code (I didn't
actually know that was possible, and looking at the docstring it says it
works more or less like `debug', which is why you got the backtrack you
mention below).

Using `edebug-all-defs' always seemed clumsy to me, and likely to cause
an explosion of unwanted effects. I would leave that as nil, and then
just use the C-u prefix argument for C-M-x (`eval-defun'). That lets you
be much more targeted about what you instrument and what you don't.

Now, when you execute the function, edebug will halt execution right at
the beginning of the function, and hand over control to you and
keybindings like "g" and "SPC" and what have you. You don't need to
insert anything into the function definition itself.

HTH,
Eric

Re: How do I get edebug online?

[Michael Heerdegen]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> You don't insert an actual call to (edebug) in your code (I didn't
> actually know that was possible, and looking at the docstring it says it
> works more or less like `debug', which is why you got the backtrack you
> mention below).

Not quite, see (info "(elisp) Source Breakpoints").  That requires the
containing function to be instrumented (which was not the case for the
OP).  In uninstrumented code it indeed just calls `debug'.

Michael.

Re: How do I get edebug online?

[Eric Abrahamsen]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>
>> You don't insert an actual call to (edebug) in your code (I didn't
>> actually know that was possible, and looking at the docstring it says it
>> works more or less like `debug', which is why you got the backtrack you
>> mention below).
>
> Not quite, see (info "(elisp) Source Breakpoints").  That requires the
> containing function to be instrumented (which was not the case for the
> OP).  In uninstrumented code it indeed just calls `debug'.

Well that was the "more or less" :)

Re: How do I get edebug online?

[Michael Heerdegen]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> Well that was the "more or less" :)

Ok :)

But jokes aside: it really can be useful - but it's better to make the
variable buffer local.

If you don't have a clue why and where something strange is happening,
it allows to instrument a whole buffer's definitions.  Then you can set
edebug-global-break-condition to a sexp that checks whether the strange
things have started, and with some luck edebug drops you directly inside
the culprit.  If not, hit "d" to check the callers and instrument some
more stuff.

Michael.

Re: How do I get edebug online?

[Emanuel Berg via Users list for the GNU Emacs text editor]

Eric Abrahamsen wrote:

>> containing function to be instrumented (which was not the
>> case for the OP). In uninstrumented code it indeed just
>> calls `debug'.
>
> Well that was the "more or less" :)

Is "more or less" the Swedish "mer eller mindre", meaning
pretty close or close enough a description of something, or
does it mean "både ock" which means both aspects are true but
in their own ways?

E.g.,

- Mr. Paul Anderson, when one speaks with you one gets the
  impression that you always try to see both sides of
  a problem?

- _________ <-- what should this be in English? It is "både
                ock" in Swedish, "mer eller mindre" which is
                literally "more or less" doesn't make sense,
                well, it isn't fun anyway :))

-- 
underground experts united
https://dataswamp.org/~incal

Re: How do I get edebug online?

[Eric Abrahamsen]

Emanuel Berg via Users list for the GNU Emacs text editor
<help-gnu-emacs@gnu.org> writes:

> Eric Abrahamsen wrote:
>
>>> containing function to be instrumented (which was not the
>>> case for the OP). In uninstrumented code it indeed just
>>> calls `debug'.
>>
>> Well that was the "more or less" :)
>
> Is "more or less" the Swedish "mer eller mindre", meaning
> pretty close or close enough a description of something, or
> does it mean "både ock" which means both aspects are true but
> in their own ways?

I think it's more like the former: an approximation that doesn't quite
fit with the facts, but close enough to be useful.

Re: How do I get edebug online?

[Michael Heerdegen]

Davin Pearson <davin.pearson@gmail.com> writes:

> First I eval the following sexp:
>
> (setq edebug-all-defs t)
>
> Then I issue the following command on the following code which resides
> in a file called:
> ~/java-training-wheels/dlisp/coolmacs/dmp-grep--splat-file.el.
> The command is \C-\M-x.  The file contains the following defun:
>
> (defun fac (n)
>   (when (= 5 n)
>     (message "Foo bar")
>     (edebug)
>     (message "Rita Hayworth"))
>   (if (< 0 n)
>       (* n (fac (1- n)))
>     1))
>
> Execute the following command:
>
> (fac 10)
>
> and it comes back at you with the following backtrace: (see after this
> backtrace for my question)
>
> Debugger entered: nil
> [...]

While I agree that in your situation it's more appropriate to call C-M-x
with prefix argument, your recipe should enable edebug nonetheless, so I
have reported your discovery as new Bug#53331.  Hard to believe that
nobody ever reported this.

Thanks,

Michael.