Tip: Debugging with function `message-box'

Tip: Debugging with function `message-box'

[Jean Louis]

I find it often easier to debug values of some variables by using the
function `message-box' instead of just `message':

(message-box "%s" "Hello")

Unlike the function `message' this one blocks the execution for a
while, or until confirmed. This is useful in various debugging
processes.

Jean

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RE: [External] : Tip: Debugging with function `message-box'

[Drew Adams]

> I find it often easier to debug values of some variables by using the
> function `message-box' instead of just `message':
> 
> (message-box "%s" "Hello")
> 
> Unlike the function `message' this one blocks the execution for a
> while, or until confirmed. This is useful in various debugging
> processes.

Sure.  Some alternatives, just for info:

To just pause so you can see the message (which gets
logged to `*Messages*' anyway), you can use `sit-for'
or `sleep-for'.  E.g. `(message "...")(sleep-for 2)'.

To block until confirmed, you can use `(debug)'.
(`c' to just confirm.)  And `(debug nil <whatever>)'
prints the <whatever> at the top of the debugger
(like a message).

Re: [External] : Tip: Debugging with function `message-box'

[Jean Louis]

* Drew Adams <drew.adams@oracle.com> [2021-06-24 21:50]:
> > I find it often easier to debug values of some variables by using the
> > function `message-box' instead of just `message':
> > 
> > (message-box "%s" "Hello")
> > 
> > Unlike the function `message' this one blocks the execution for a
> > while, or until confirmed. This is useful in various debugging
> > processes.
> 
> Sure.  Some alternatives, just for info:
> 
> To just pause so you can see the message (which gets
> logged to `*Messages*' anyway), you can use `sit-for'
> or `sleep-for'.  E.g. `(message "...")(sleep-for 2)'.
> 
> To block until confirmed, you can use `(debug)'.
> (`c' to just confirm.)  And `(debug nil <whatever>)'
> prints the <whatever> at the top of the debugger
> (like a message).

Good tips.

When there is something wrong I am also using C-u C-M-x to instrument
the function then I can go step by step verifying what is happening.


-- 
Jean

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RE: [External] : Tip: Debugging with function `message-box'

[Drew Adams]

> When there is something wrong I am also using C-u C-M-x to instrument
> the function then I can go step by step verifying what is happening.

1. That's `edebug', one of the Lisp debuggers for Emacs.

https://www.gnu.org/software/emacs/manual/html_node/elisp/Edebug.html

2. Plain `debug' is another Lisp debugger for Emacs.

https://www.gnu.org/software/emacs/manual/html_node/elisp/Debugger.html

 * `debug-on-entry' to debug on entry to a function,
   including a built-in (coded in C).  (And some C
   code calls Lisp functions.)

 * Non-nil `debug-on-error', to just see a backtrace.

 * Place calls to `debug' in code as breakpoints,
   i.e., places where the debugger is entered.

3. GUD is another debugger you can use with Emacs.

https://www.gnu.org/software/emacs/manual/html_node/emacs/Debuggers.html
____

They all let you go step by step.