disable debug-on-error in emacs -Q?

disable debug-on-error in emacs -Q?

[Stephen Leake]

I'm trying to write a bug report about an error message.

But when I start emacs with -Q, it _always_ enters the debugger when the
error is signaled, even if I explicitly set debug-on-error to nil.

In addition, the Options menu shows debug on error to be disabled.

I can understand why debug-on-error would be set to t with -Q, but why
is setting it nil ignored?

How do I get the error message for the bug report?

-- 
-- Stephe

Re: disable debug-on-error in emacs -Q?

[Andreas Schwab]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> But when I start emacs with -Q, it _always_ enters the debugger when the
> error is signaled,

Which version?  Where do you get the error?  Emacs doesn't behave
differently with -Q in this respect.

> I can understand why debug-on-error would be set to t with -Q, but why
> is setting it nil ignored?

Worksforme.  Outside of eval-expression, Emacs respects the setting of
debug-on-error.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: disable debug-on-error in emacs -Q?

[Stephen Leake]

Andreas Schwab <schwab@linux-m68k.org> writes:

> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> But when I start emacs with -Q, it _always_ enters the debugger when the
>> error is signaled,
>
> Which version?  

I've tried Emacs 24.5 and emacs-25 branch, on Windows/MinGW64 and Debian
on VMWare/Windows.

> Where do you get the error? 

I'm testing with:

(+ "foo" 2)

evaluated in the scratch buffer with C-j. Same result evaluating via M-:.

> Emacs doesn't behave differently with -Q in this respect.

It does for me.

With just "emacs", the above puts an error message in *Messages* if
`debug-on-error' is nil.

With "emacs -Q", it opens the *Backtraces* buffer independent of
`debug-on-error'.


I found a workaround; eval the expression once to get *Backtraces*.
Then eval it again without quiting the debugger; that gives the error
message.

-- 
-- Stephe

Re: disable debug-on-error in emacs -Q?

[Michael Heerdegen]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> evaluated in the scratch buffer with C-j. Same result evaluating via
> M-:.

Are you missing `eval-expression-debug-on-error'?


Michael.

Re: disable debug-on-error in emacs -Q?

[Stephen Leake]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> evaluated in the scratch buffer with C-j. Same result evaluating via
>> M-:.
>
> Are you missing `eval-expression-debug-on-error'?

That symbol is not defined, so yes, I am missing it.

What would that do for me?

-- 
-- Stephe

Re: disable debug-on-error in emacs -Q?

[Michael Heerdegen]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> > Are you missing `eval-expression-debug-on-error'?
>
> That symbol is not defined, so yes, I am missing it.

This user option was introduced in Emacs 21.1, and is defined in
simple.el.  I don't understand how it can be undefined for you.

> What would that do for me?

Solve your problem and answer your question.


Michael.

Re: disable debug-on-error in emacs -Q?

[Stephen Leake]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> Michael Heerdegen <michael_heerdegen@web.de> writes:
>
>> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>>
>>> evaluated in the scratch buffer with C-j. Same result evaluating via
>>> M-:.
>>
>> Are you missing `eval-expression-debug-on-error'?
>
> That symbol is not defined, so yes, I am missing it.

I searched for a function; it seems it is a variable.

-- 
-- Stephe

Re: disable debug-on-error in emacs -Q?

[Andreas Schwab]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> I'm testing with:
>
> (+ "foo" 2)
>
> evaluated in the scratch buffer with C-j. Same result evaluating via M-:.

Worksasdesigned.

C-h v eval-expression-debug-on-error

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: disable debug-on-error in emacs -Q?

[Stephen Leake]

Andreas Schwab <schwab@linux-m68k.org> writes:

> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> I'm testing with:
>>
>> (+ "foo" 2)
>>
>> evaluated in the scratch buffer with C-j. Same result evaluating via M-:.
>
> Worksasdesigned.
>
> C-h v eval-expression-debug-on-error

Ah; that is listed in the info node "Entering Debugger on an Error".
Apparently I missed it the first time I read that node.

Thanks for the pointer.

-- 
-- Stephe

Re: disable debug-on-error in emacs -Q?

[Noam Postavsky]

On Tue, Dec 1, 2015 at 11:54 AM, Stephen Leake
<stephen_leake@stephe-leake.org> wrote:
> I'm testing with:
>
> (+ "foo" 2)
>
> evaluated in the scratch buffer with C-j. Same result evaluating via M-:.

Both of those methods use eval-expression-debug-on-error rather than
debug-on-error, try

(defun foo ()
  (interactive)
  (+ "foo" 2))

And then M-x foo, instead.

>> Emacs doesn't behave differently with -Q in this respect.
>
> It does for me.

Presumable you have set eval-expression-debug-on-error to nil in your init file.

> I found a workaround; eval the expression once to get *Backtraces*.
> Then eval it again without quiting the debugger; that gives the error
> message.

Hitting c (debugger-continue) from *Backtraces* should also work.

Re: disable debug-on-error in emacs -Q?

[Stephen Leake]

Noam Postavsky <npostavs@users.sourceforge.net> writes:

> Presumable you have set eval-expression-debug-on-error to nil in your
> init file.

Yes, I do, in custom-set-variables. I must have done that a _long_ time
ago; I've totally forgotten about it.

>> I found a workaround; eval the expression once to get *Backtraces*.
>> Then eval it again without quiting the debugger; that gives the error
>> message.
>
> Hitting c (debugger-continue) from *Backtraces* should also work.

Ah. I was not aware of that command.

(there's only a million or so Emacs commands to learn ...)

Thanks.

-- 
-- Stephe

RE: disable debug-on-error in emacs -Q?

[Drew Adams]

> > Hitting c (debugger-continue) from *Backtraces* should also work.
> Ah. I was not aware of that command.
> (there's only a million or so Emacs commands to learn ...)

Ask Emacs: `C-h m' =>

Debugger mode defined in `debug.el' (`debugger-mode'):
Mode for backtrace buffers, selected in debugger.

A line starts with `*' if exiting that frame will call the debugger.
Type b or u to set or remove the `*'.

When in debugger due to frame being exited,
use the r command to override the value
being returned from that frame.

Use M-x debug-on-entry and M-x cancel-debug-on-entry to control
which functions will enter the debugger when called.

Complete list of commands:
key             binding
---             -------

0 .. 9          digit-argument
TAB             forward-button
RET             debug-help-follow
ESC             Prefix Command
SPC             next-line
-               negative-argument
R               debugger-record-expression
b               debugger-frame
c               debugger-continue
d               debugger-step-through
e               debugger-eval-expression
h               describe-mode
j               debugger-jump
l               debugger-list-functions
q               top-level
r               debugger-return-value
u               debugger-frame-clear
v               debugger-toggle-locals
...

This mode runs the hook `debugger-mode-hook', as the final step
during initialization.