23.0.60; scroll-up gives something between error and message

23.0.60; scroll-up gives something between error and message

[Lennart Borgman (gmail)]

There is something strange with the error handling in scroll-up. When 
calling (scroll-up 1) in an empty buffer execution of the function 
calling it stopped and a message is given. However there is no error 
generated.

To see this start from

    emacs -Q

and evaluate the following function and run it:

(defun test-scroll ()
   (interactive)
   (setq debug-on-error t)
   (let* ((buffer-name "test-scroll")
         (buffer (get-buffer buffer-name)))
     (when buffer (kill-buffer buffer))
     (setq buffer (get-buffer-create buffer-name))
     (switch-to-buffer buffer)
     (message "here 1") (sit-for 2)
     (scroll-up 1)
     (message "here 2") (sit-for 2)
     ))



In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
  of 2008-03-21
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags 
-Ic:/g/include -fno-crossjumping'

Re: 23.0.60; scroll-up gives something between error and message

[Stefan Monnier]

> There is something strange with the error handling in scroll-up. When
> calling (scroll-up 1) in an empty buffer execution of the function calling
> it stopped and a message is given. However there is no error generated.

What makes you think no error is generated?


        Stefan

Re: 23.0.60; scroll-up gives something between error and message

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
>> There is something strange with the error handling in scroll-up. When
>> calling (scroll-up 1) in an empty buffer execution of the function calling
>> it stopped and a message is given. However there is no error generated.
> 
> What makes you think no error is generated?


There is no traceback, but yes I did not try. Here is a try:

(defun test-scroll ()
   (interactive)
   (setq debug-on-error t)
   (let* ((buffer-name "test-scroll")
         (buffer (get-buffer buffer-name)))
     (when buffer (kill-buffer buffer))
     (setq buffer (get-buffer-create buffer-name))
     (switch-to-buffer buffer)
     (message "here 1") (sit-for 1)
     (condition-case err
         (scroll-up 1)
       (error (message "scroll-up error: %s" err)
              (sit-for 1)))
     (message "here 2") (sit-for 1)
     (scroll-up 1)
     (message "here 3") (sit-for 1)
     ))

The output is now

here 1
scroll-up error: (end-of-buffer)
here 2
let*: End of buffer

There is no *Backtrace* window shown for the second (scroll-up 1). Is 
there when you test it?

Re: 23.0.60; scroll-up gives something between error and message

[Stefan Monnier]

>>> There is something strange with the error handling in scroll-up. When
>>> calling (scroll-up 1) in an empty buffer execution of the function calling
>>> it stopped and a message is given. However there is no error generated.
>> 
>> What makes you think no error is generated?


> There is no traceback, but yes I did not try.

Your test shows that an error is indeed signalled.
Check debug-ignored-errors.


        Stefan

Re: 23.0.60; scroll-up gives something between error and message

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
>>>> There is something strange with the error handling in scroll-up. When
>>>> calling (scroll-up 1) in an empty buffer execution of the function calling
>>>> it stopped and a message is given. However there is no error generated.
>>> What makes you think no error is generated?
> 
> 
>> There is no traceback, but yes I did not try.
> 
> Your test shows that an error is indeed signalled.
> Check debug-ignored-errors.


Oh, no, not once again. Sorry.

How about adding something to the error string, like "(ignored error)"? 
Or maybe that is complicated.