bug#7461: 23.2; Gdb only does tab completion inside Emacs when prompt is (gdb)

bug#7461: 23.2; Gdb only does tab completion inside Emacs when prompt is (gdb)

[Rolando Pereira]

When running gdb inside emacs, either by doing M-x gdb or M-x gud-gdb,
if the prompt is set to something that isn't "(gdb)" (or similar, see
the examples below), pressing TAB doesn't do the completion of
commands, functions or variables.

Use the following steps to reproduce the error using emacs -Q:

1) Create a new C file, for example code.c, with the following
contents:

#include <stdio.h>

int main(void) {
	printf("Hello World\n");
	return 0;
}

2) Compile code using gcc -g code.c -o code

3) Open emacs -Q

4) Start debugging the file using M-x gdb

5) Prompt should be "(gdb) ". Try to type "b ma" and press TAB. It
should expand to "b main".

6) Change gdb's prompt to something else using "set prompt". I changed
it to "gdb> ".

7) Try to type "b ma" and press TAB. It should display on the
minibuffer the message "No completions of ma".


Prompts I've tried where TAB completion still worked:

* "(gdb)"
* "        (gdb)        " (the prefix whitespace is discarded by gdb,
  so this is the same as "(gdb)        ")
* "( gdb) "
* "(gdb)_______________________"
* "(GDB) "
* "( GDB) "

Prompts I've tried where TAB completion DIDN'T work:

* "(gdb )"
* "_(gdb)"
* "(gdb "
* "gdb) "
* "( gdb )"
* "" (removed prompt by typing "set prompt" in gdb)
* "gdb> "
* "gdb>"
* "gdb "
* "gdb"
* "<gdb "
* "<gdb"

Emacs version is: GNU Emacs 23.2.1 (i686-pc-linux-gnu, GTK+ Version
2.16.1)

GDB version is: GNU gdb (GDB) 7.2

bug#7461: 23.2; Gdb only does tab completion inside Emacs when prompt is (gdb)

[Glenn Morris]

Rolando Pereira wrote:

> When running gdb inside emacs, either by doing M-x gdb or M-x gud-gdb,
> if the prompt is set to something that isn't "(gdb)" (or similar, see
> the examples below), pressing TAB doesn't do the completion of
> commands, functions or variables.

Thank you for the complete example.

It looks like, after you have changed the prompt, you can set the
local value of comint-prompt-regexp to match it.

More generally, when comint-use-prompt-regexp is nil (which it is by
default), gud.el probably ought not to try and use comint-prompt-regexp.
Instead it should use whatever field properties comint adds.

> Emacs version is: GNU Emacs 23.2.1 (i686-pc-linux-gnu, GTK+ Version
> 2.16.1)
>
> GDB version is: GNU gdb (GDB) 7.2

bug#7461: 23.2; gud.el always uses comint-prompt-regexp; things can break if prompt is changed

[Lars Ingebrigtsen]

Glenn Morris <rgm@gnu.org> writes:

>> When running gdb inside emacs, either by doing M-x gdb or M-x gud-gdb,
>> if the prompt is set to something that isn't "(gdb)" (or similar, see
>> the examples below), pressing TAB doesn't do the completion of
>> commands, functions or variables.
>
> Thank you for the complete example.
>
> It looks like, after you have changed the prompt, you can set the
> local value of comint-prompt-regexp to match it.
>
> More generally, when comint-use-prompt-regexp is nil (which it is by
> default), gud.el probably ought not to try and use comint-prompt-regexp.
> Instead it should use whatever field properties comint adds.

(I'm going through old bug reports that unfortunately weren't
resolved at the time.)

Looking at the gud code, that sounds like a good idea --- but
unfortunately comint doesn't put any specific field property on the
prompt.  Instead it seems like it marks all the data output, including
the prompt, as `output'.  Which makes sense, but doesn't help us with
distinguishing whether the line we're at is a prompt.

I think.

And I don't think we can change the fields here, because I'm guessing a
lot of stuff depends on all the output being the same field.

But comint does indeed know that it's a prompt...  so we could add
another property here -- like `comint-prompt' on the prompts, and then
use that.

Anybody have any other ideas here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no