Subject: bug#22984: 25.0.92; Typo in etc/DEBUG

From: [email-masked] (N. Jackson)
Date: Fri, 11 Mar 2016 14:30:29 -0400

At 17:59 +0200 on Friday 2016-03-11, Eli Zaretskii wrote:
>
>> Additionally, it might be helpful if this file mentioned the "debugger"
>> that pops up when debug-on-error is non-nil.
>
> That's not really what that file is about.
>
>> This "debugger" doesn't seem to be a debugger at all, but just a
>> help window with a backtrace in it.
>
> No, it's a debugger.  See the node "Debugger" in the ELisp manual, it
> is described there.

I see. Thank you.

However, the file is named "DEBUG" and the title is "Debugging GNU
Emacs", so it is by no means obvious that this is not the right file to
look at.

So perhaps the title should be something like "Debugging GNU Emacs with
GDB", and perhaps it should start out by saying something along the
lines of

    This file is about debugging Emacs with GDB.  For information about
    the Lisp debugger and about Edebug (the source-level debugger for
    Emacs Lisp programs), see the node "Debugging" in the Elisp manual.

>> Also, can one use `M-x gdb RET' in the same instance of Emacs that one
>> wishes to debug?
>
> No, of course not.  When you attach GDB to a program, GDB stops its,
> so Emacs will stop responding, and you will not be able to continue
> debugging.
>
> But you can run a second instance of the same binary, and debug the
> first instance from that second instance.  Perhaps this is what you
> had in mind, and this is just a misunderstanding caused by the vague
> meaning of "instance"?

Hah, no. I've only ever used GDB from the command line. It seemed like
an (insanely) neat trick if you could run GDB in the same instance of
Emacs as one was debugging. It was my fuzzy thinking along with the
following sentence that led me astray:

    This will suggest the default binary to debug; if you are going to
    start a new Emacs process, change it as needed to point to the
    correct binary.

I think the full meaning of this sentence only becomes clear after one
reads the following sentence:

    Alternatively, if you want to attach the debugger to an already
    running Emacs process...

The problems with the first sentence are "you", "new", and "it". Perhaps
it could be made slightly clearer?

Perhaps something along the lines of:

    This will suggest the default binary for GDB to start; if you want
    GDB to start a different binary, change the suggestion as needed.
    Alternatively, if you want to attach GDB to an already running Emacs
    process...

Regards,
N.